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Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    The risks of drinking sugar sweetened drinks | WURcast
    Kampman, E. - \ 2019
    Wageningen : WURcast
    sugar - health - diseases - blood sugar - carbohydrates - soft drinks
    The consumption of sugar-sweetened drinks increases rapidly. What is the danger of these drinks? This lesson is part of the WageningenX MOOC called 'Nutrition and Cancer'.
    Evaluation of fungal degradation of wheat straw cell wall using different analytical methods from ruminant nutrition perspective
    Nayan, Nazri ; Erven, Gijs van; Kabel, Mirjam A. ; Sonnenberg, Anton S.M. ; Hendriks, Wouter H. ; Cone, John W. - \ 2019
    Journal of the Science of Food and Agriculture 99 (2019)8. - ISSN 0022-5142 - p. 4054 - 4062.
    carbohydrates - in vitro gas production - lignin - lignin quantification - pyrolysis-GC/MS - white-rot fungi

    BACKGROUND: White rot fungi have been used to improve the nutritive value of lignocellulose for ruminants. In feed analysis, the Van Soest method is widely used to determine the cell wall contents. To assess the reliability of this method (Method A) for determination of cell wall contents in fungal-treated wheat straw, we compared a combined monosaccharide analysis and pyrolysis coupled to gas chromatography with mass spectrometry (Py-GC/MS) (Method B). Ruminal digestibility, measured as in vitro gas production (IVGP), was subsequently used to examine which method explains best the effect of fungal pretreatment on the digestibility of wheat straw. RESULTS: Both methods differed considerably in the mass recoveries of the individual cell wall components, which changed on how we assess their degradation characteristics. For example, Method B gave a higher degradation of lignin (61.9%), as compared to Method A (33.2%). Method A, however, showed a better correlation of IVGP with the ratio of lignin to total structural carbohydrates, as compared to Method B (Pearson's r of −0.84 versus −0.69). Nevertheless, Method B provides a more accurate quantification of lignin, reflecting its actual modification and degradation. With the information on the lignin structural features, Method B presents a substantial advantage in understanding the underlying mechanisms of lignin breakdown. Both methods, however, could not accurately quantify the cellulose contents – among others, due to interference of fungal biomass. CONCLUSION: Method A only accounts for the recalcitrant residue and therefore is more suitable for evaluating ruminal digestibility. Method B allows a more accurate quantification of cell wall, required to understand and better explains the actual modification of the cell wall. The suitability of both methods, therefore, depends on their intended purposes.

    Direct and Long-Term Metabolic Consequences of Lowly vs. Highly-Digestible Starch in the Early Post-Weaning Diet of Mice
    Fernández-Calleja, José M.S. ; Bouwman, Lianne M.S. ; Swarts, Hans J.M. ; Oosting, Annemarie ; Keijer, Jaap ; Schothorst, Evert M. van - \ 2018
    Nutrients 10 (2018)11. - ISSN 2072-6643
    adipose tissue - amylopectin - amylose - C57BL mice - carbohydrates - glycemic index - indirect calorimetry - metabolic flexibility - nutrition - sexual dimorphism

    Starches of low and high digestibility have different metabolic effects. Here, we examined whether this gives differential metabolic programming when fed in the immediate post-weaning period. Chow-fed mice were time-mated, and their nests were standardized and cross-fostered at postnatal days 1⁻2. After postnatal week (PW) 3, individually housed female and male offspring were switched to a lowly-digestible (LDD) or highly-digestible starch diet (HDD) for three weeks. All of the mice received the same high-fat diet (HFD) for nine weeks thereafter. Energy and substrate metabolism and carbohydrate fermentation were studied at the end of the HDD/LDD and HFD periods by extended indirect calorimetry. Glucose tolerance (PW 11) and metabolic flexibility (PW14) were analyzed. Directly in response to the LDD versus the HDD, females showed smaller adipocytes with less crown-like structures in gonadal white adipose tissue, while males had a lower fat mass and higher whole body fat oxidation levels. Both LDD-fed females and males showed an enlarged intestinal tract. Although most of the phenotypical differences disappeared in adulthood in both sexes, females exposed to LDD versus HDD in the early post-weaning period showed improved metabolic flexibility in adulthood. Cumulatively, these results suggest that the type of starch introduced after weaning could, at least in females, program later-life health.

    Human Milk Oligosaccharides in Colostrum and Mature Milk of Chinese Mothers : Lewis Positive Secretor Subgroups
    Elwakiel, M. ; Hageman, J.A. ; Wang, W. ; Szeto, I.M. ; Goudoever, J.B. van; Hettinga, K.A. ; Schols, H.A. - \ 2018
    Journal of Agricultural and Food Chemistry 66 (2018)27. - ISSN 0021-8561 - p. 7036 - 7043.
    carbohydrates - genetic polymorphisms - lactation stage - variability

    To study the variability in human milk oligosaccharide (HMO) composition of Chinese human milk over a 20-wk lactation period, HMO profiles of 30 mothers were analyzed using CE-LIF. This study showed that total HMO concentrations in Chinese human milk decreased significantly over a 20-wk lactation period, independent of the mother's SeLe status, although with individual variations. In addition, total acidic and neutral HMO concentrations in Chinese human milk decreased over lactation, and levels are driven by their mother's SeLe status. Analysis showed that total neutral fucosylated HMO concentrations in Chinese human milk were higher in the two secretor groups as compared to the nonsecretor group. On the basis of the total neutral fucosylated HMO concentrations in Chinese human milk, HMO profiles within the Se+Le+ group can be divided into two subgroups. HMOs that differed in level between Se+Le+ subgroups were 2′FL, DF-L, LNFP I, and F-LNO. HMO profiles in Dutch human milk also showed Se+Le+ subgroup division, with 2′FL, LNT, and F-LNO as the driving force.

    No Adverse Programming by Post-Weaning Dietary Fructose of Body Weight, Adiposity, Glucose Tolerance, or Metabolic Flexibility
    Bouwman, Lianne M.S. ; Fernández-Calleja, José M.S. ; Swarts, Hans J.M. ; Stelt, Inge van der; Oosting, Annemarie ; Keijer, Jaap ; Schothorst, Evert M. van - \ 2018
    Molecular Nutrition & Food Research 62 (2018)2. - ISSN 1613-4125
    carbohydrates - indirect calorimetry - metabolic programming - metabolism - monosaccharides
    Scope: Metabolic programming can occur not only in the perinatal period, but also post-weaning. This study aims to assess whether fructose, in comparison to glucose, in the post-weaning diet programs body weight, adiposity, glucose tolerance, metabolic flexibility, and health at adult age. Methods and results: Three-week-old male and female C57BL6/JRccHsd mice are given an intervention diet with 32 energy percent (en%) glucose or fructose for only 3 weeks. Next, all animals are switched to the same 40 en% high fat diet for 9 weeks. Neither body weight nor adiposity differs significantly between the animals fed with glucose or fructose diets at any point during the study in both sexes. Glucose tolerance in adulthood is not affected by the post-weaning diet, nor are activity, energy expenditure, and metabolic flexibility, as measured by indirect calorimetry. At the end of the study, only in females fasting serum insulin levels and HOMA-IR index are lower in post-weaning fructose versus glucose diet (p = 0.02), without differences in pancreatic β-cell mass. Conclusions: Our present findings indicate no adverse programming of body weight, adiposity, glucose tolerance, and metabolic flexibility by dietary (solid) fructose in comparison to glucose in the post-weaning diet in mice.
    Probing the bacterial cell wall with chemical biology tools
    Sminia, Tjerk J. - \ 2017
    Wageningen University. Promotor(en): H. Zuilhof; W.M. de Vos, co-promotor(en): T. Wennekes. - Wageningen : Wageningen University - ISBN 9789463437080 - 196
    bioengineering - sugars - labelling - synthesis - biochemical techniques - akkermansia muciniphila - gastrointestinal microbiota - carbohydrates - bioengineering - suikers - etiketteren - synthese - biochemische technieken - akkermansia muciniphila - microbiota van het spijsverteringskanaal - koolhydraten

    After DNA and proteins, carbohydrates are the third language of life. Chapter 1 introduces the reader to this class of biomolecules, also called sugars or glycans, that can be found on the outer surface of almost all cells and plays a critical role as the social messengers of a cell. Although our knowledge about the role of glycans in eukaryotic cells has increased considerably in recent decades, our understanding of the glycan layer on bacterial cells is still very limited. Besides the carbohydrates that are present in both eukaryotes and prokaryotes an additional wide range of unique (e.g. microbial sialic acid), often very complex (e.g. pseudaminic acid), carbohydrates is present in prokaryotes. This chapter briefly introduces two research fields, carbohydrate chemistry and chemical biology, that when combined provide a powerful way to investigate the biological role of these unique bacterial carbohydrates at the molecular level. This chemistry-based approach, termed chemical microbiology, often starts with the development of a chemical synthesis for a target bacterial carbohydrate. Subsequently, the synthetic route towards this target allows for the introduction of unnatural functional groups, like chemical reporters, that result in the molecular tools needed to study their biological function. The studies described in this thesis, focus on developing such molecular tools to study the role of glycans and glycoconjugates in human gut bacteria and human-associated bacteria.

    Chapter 2 provides an overview of metabolic oligosaccharide engineering (MOE) a popular chemical biology technique to label glycans in living cells. In MOE, carbohydrates derivatives are synthesised with unnatural chemical reporters and used to study their incorporation in glycans of eukaryote to prokaryote species. The progress in this field over the last 6 years is reviewed in detail with a special emphasis on the synthesis of the unnatural carbohydrates from commercially available sources. The principle behind MOE is that these unnatural carbohydrates with e.g. azide, alkyne, cyclopropene, or isonitrile chemical reporter groups, are still recognised by the endogenous enzymes in the cell that salvage this new carbohydrate. In this way they can enter the associated biochemical pathways and end up in newly biosynthesised cellular glycans. Subsequent labelling techniques, such as strain promoted azide alkyne cycloaddition or tetrazine ligation, enable the visualisation of these incorporated unnatural carbohydrates with for instance fluorescence microscopy.

    Metabolic labelling is further explored in chapter 3. Key cell envelope glycoconjugates in the mucin-degrading gut microbiota member, Akkermansia muciniphila, were subjected to chemistry-based functional analysis, with Escherichia coli being used as a control species. Two novel non-toxic peptidoglycan (PG) probes were designed and synthesised to investigate the presence of PG in this species. Their design was based on the natural d-alanine dipeptide motif found in PG. Inspired by the fact that d-alanine dipeptide-derivatives were previously reported to be incorporated in newly synthesised PG, we synthesised a cyclopropene and isonitrile d-alanine dipeptide. Our probes proved to be non-toxic, as shown by growth and viable count analysis, and were therefore superior over existing PG probes. Another beneficial property was that the probes also did not influence the specific growth rate of A. muciniphila or E. coli. The PG probes were successfully incorporated into the peptidoglycan layer of A. muciniphila and visualised using a tetrazine click-ligation with a fluorophore. Our analysis proved for the first time that A. muciniphila has a PG layer. Besides PG labelling, we also investigated metabolic labelling of other glycoconjugates on the outer surface of A. muciniphila. This part of the study showed that azido-monosaccharide derivatives of N-acetylglucosamine, N-acetylgalactosamine, and fucose are successfully processed by A. muciniphila salvage pathways and incorporated into its surface glycoconjugates. Especially 6-azido-fucose was readily processed by the recently discovered l-fucose salvage pathway of A. muciniphila. The two compatible labelling techniques were next combined in a dual labelling experiment. Our isonitrile dipeptide peptidoglycan probe and 6-azido-fucose were successfully incorporated into A. muciniphila. Subsequent fluorescent labelling with bio-orthogonal techniques resulted in dual labelling of peptidoglycan and fucose-containing glycans in live A. muciniphila cells.

    With the positive results of MOE in A. muciniphila in hand, chapter 4 describes the further investigation of MOE. After successful validation of our Ac4FucAz probe for MOE in Bacteroides fragilis we continued their application in other human gut microbiota members, including the butyrate-producing Anaerostipes rhamnosivorans, Intestimonas butyriciproducens, and Eubacterium hallii. Labelling of these human gut microbes proved to be rather challenging with a-specific cellular labelling with the fluorophore being the major problem. Initial results, however, did show that a 6-azido-l-rhamnose probe resulted in fluorescent labelling of A. rhamnosivorans, which provides initial evidence for the existence of an as of yet undocumented salvage pathway. In this species the 6-azido-fucose probe was not salvaged. Via confocal microscopy and flow cytometry analysis we observed that the 6-azido-rhamnose probe was selective for A. rhamnosivorans in the presence of A. muciniphila. Such a co-culture experiment is a first step in mimicking the complex human gut microbiome. For E. hallii Ac4GalNAz gave clear metabolic labelling and the majority of the cell population could be labelled with the fluorescent dye after a strain-promoted azide alkyne cycloaddition. Other glycan probes (Ac4GlcNAz, Ac4FucAz, and Neu5Az) also resulted in labelling, but not as prominent as Ac4GalNAz. Surprisingly, MOE has never been reported for the common lab strain Escherichia coli MG1655. Curious to investigate this in more detail we started MOE in E. coli. However, no labelling was obtained when Ac4GlcNAz probe was added to E. coli, most likely due to the fast growth, metabolism and turnover. Only, when fresh Ac4GlcNAz probe was added every 30 minutes, metabolic labelling in E. coli was observed. To further investigate the influence of GlcNAc metabolism in E. coli on MOE, single-gene knock-outs of E. coli GlcNAc metabolism from the Keio collection were investigated. Labelling was observed for NagA (N-acetyl glucosamine 6 P deacetylase) and NagK (N-acetyl-d-glucosamine kinase) E. coli mutants. Both enzymes are involved in the last step of the biosynthesis towards UDP-N-acetylglucosamine. When the overall E. coli metabolism was inhibited, after addition of the respiration inhibitor sodium azide, no metabolic labelling was observed. These results indicate that MOE in E. coli is possible, but challenging and can only be performed under specific circumstances.

    An investigation into the total synthesis of pseudaminic acid, a sialic acid produced by specific human-associated prokaryotes, is described in chapter 5. Sialic acids are typically found at the terminal positions of surface glycoconjugates in both eukaryotes and prokaryotes. Other related microbial sialic acids are legionaminic and acinetaminic acid. The total synthesis of these microbial sialic acids is notoriously difficult, as exemplified by the fact that only a few chemical synthesis routes towards them are currently known. Our total synthesis of pseudaminic acid started from the readily available amino acid l-threonine that was transformed into a key versatile Garner aldehyde derivative intermediate. With this aldehyde in hand, the Henry nitro-aldol condensation reaction was investigated. After studying numerous conditions, such as asymmetric catalysis or elongated reaction times, and extensive optimisation efforts we were never able to obtain the Henry reaction product to continue with this route. As an alternative, a tethered aminohydroxylation was investigated for its ability to introduce the key functional group and stereochemistry onto an intermediate obtained from the Garner aldehyde derivative. This reaction indeed gave the desired amino-alcohol motif in the correct stereochemistry, but another diastereomer proved very difficult to separate from the desired product. After some additional transformations and protection steps we obtained a derivative in which the primary alcohol could be oxidised to provide a hexose intermediate that resembles the hexose intermediate present in pseudaminic acid biosynthesis. This key hexose intermediate will likely enable a subsequent Barbier reaction, a chain elongation step, in future studies. With most of the key transformations accomplished, the completion of a pseudaminic total synthesis based on l-threonine should soon be possible. Besides finishing the total synthesis, future work should also focus on adapting this synthesis route to allow installation of chemical reporter groups on pseudaminic acid for its application in MOE.

    Chapter 6 is the general discussion about all the work mentioned in the other chapters. It also contains additional information and suggestions for further research in the field of chemical microbiology.

    The evaluation of energy in fish feed
    Haidar, Mahmoud - \ 2017
    Wageningen University. Promotor(en): J.A.J. Verreth, co-promotor(en): J.W. Schrama. - Wageningen : Wageningen University - ISBN 9789463438049 - 155
    oreochromis niloticus - fish feeding - feed formulation - digestible energy - dietary protein - dietary fat - carbohydrates - growth - feed evaluation - fish culture - aquaculture - oreochromis niloticus - visvoeding - voersamenstelling - verteerbare energie - voedingseiwit - voedingsvet - koolhydraten - groei - voederwaardering - visteelt - aquacultuur

    New and alternative plant ingredients are increasingly incorporated in fish feed due to the scarcity of captured fish and increased fishmeal and fish oil prices. As a result, current fish feeds are characterized by a highly variable ingredients composition, leading to a similar variability in the dietary macronutrients composition, especially the carbohydrates fraction. Appropriate formulation of the energy component in fish feeds requires information on nutrient digestibility, energy requirements for maintenance, and the efficiency of utilization of digestible energy for growth (kgDE). In fish feed formulation, the energy evaluation is based on digestible energy (DE) basis. The main assumptions of this DE system are that maintenance requirements and kgDE are independent of dietary factors. The main objective of this thesis was to evaluate and improve the DE system for Nile tilapia. Data showed that, opposite to what is assumed in literature and irrespective of the feeding level applied, an optimal digestible protein to digestible energy ratio (DP/DE) for young Nile tilapia could not be detected. In addition, it was expected that Nile tilapia would show a maximal protein deposition in relation to a wide range of DP/DE ratios, however, this was either observed. Further investigations showed that different body compartments/organs responded differently in terms of protein and fat composition as a result of changes in the dietary DP/DE ratio. In tilapia, viscera and the “rest” fraction (head, skin, fins and bones) were the main site for fat retention. In addition, protein content of fillets seems to be constant (about 17%) and not affected by dietary factors in Nile tilapia. In addition, the effect of using new plant ingredients in Nile tilapia diets was also investigated. The results showed that the ingredients composition had an effect on the maintenance requirements of Nile tilapia. Further, changes in the ratio of starch vs non starch carbohydrates revealed that energy retention was lower when more dietary fibers were included. In addition, the net energy retention differed also when the levels of digestible protein, fat and carbohydrates changed in the diets. The latter results proved that kgDE was not constant and was dependent on diet composition. All aforementioned results led us to calculate the energetic efficiencies of digestible protein, fat and carbohydrates for net energy retention. These estimated efficiencies were used to propose a net energy evaluation system being feasible for Nile tilapia.

    Samenstelling van blad, stengel en rhizomen in relatie tot optimaal oogst-tijdstip van Miscanthus x giganteus
    Kasper, G.J. ; Kolk, J.C. van der; Putten, J.C. van der - \ 2017
    Wageningen : Wageningen Livestock Research (Wageningen Livestock Research rapport 1022) - 27
    brandstofgewassen - biobased economy - miscanthus - grassen - oogsttijdstip - gewasopbrengst - akkerbouw - plantensamenstelling - suikergehalte - lignine - pectinen - droge stof - koolhydraten - stengels - wortelstokken - fuel crops - biobased economy - miscanthus - grasses - harvesting date - crop yield - arable farming - plant composition - sugar content - lignin - pectins - dry matter - carbohydrates - stems - rhizomes
    A plurality of components (such as sugars, lignin, pectin) of Miscanthus x giganteus has been studied in stem, leaf, and rhizomes for the harvest times July and January in view of the optimal harvest time. Additional literature search shows that the end of October is the optimum time for harvesting on the basis of the maximum above-ground dry matter yield and sugar yield, and dry matter yield in the next year. It will have to be investigated whether the optimal harvest time also applies to long-term research.
    Mild disintegration of green microalgae and macroalgae
    Postma, Richard - \ 2016
    Wageningen University. Promotor(en): Michel Eppink; Rene Wijffels, co-promotor(en): Giuseppe Olivieri. - Wageningen : Wageningen University - ISBN 9789462579477 - 181
    algae - chlorella vulgaris - bioprocess engineering - biorefinery - proteins - milling - carbohydrates - biobased economy - disintegrators - technology - extraction - algen - chlorella vulgaris - bioproceskunde - bioraffinage - eiwitten - maling - koolhydraten - biobased economy - desintegrators - technologie - extractie

    An increased worldwide protein demand for food and feed and the necessity to release the water soluble proteins in the first stage of the cascade biorefinery require the development of mild protein extraction technologies. Cell disintegration is the first hurdle and is considered as one of the most energy consuming steps. Therefore, this thesis focused on the development of a mild, scalable and energy efficient disintegration technology for green microalgae and macroalgae (seaweed) aimed on extraction of water soluble components (like proteins and carbohydrates).

    For microalgae disintegration, two main technologies were investigated. First of all the conventional technology bead milling and second a novel approach using Pulsed Electric Field (PEF). In Chapter 2 a benchmark was set by means of bead milling for the release of water soluble protein from the green microalgae Chlorella vulgaris. Overall, protein yields between 32 and 42% were achieved, while the energy consumption was reduced with 85% by selective protein extraction to values as low as 0.81 kWh kgDW-1. Remarkably, the benchmark was much better than expected.

    In Chapter 3 the bead mill was further optimized by decreasing the applied bead size, furthermore the applicability of bead milling on two additional microalgae species (Neochloris oleoabundans, Tetraselmis suecica) was shown. In addition, to be able to better understand the disintegration mechanism, the so-called stress model was applied. This model describes the comminution process in a bead mill as function of the amount of bead contacts and the force of each impact. The release kinetics could be improved and thereby the specific energy consumption could be reduced to 0.45‒0.47 kWh kgDW-1 by using 0.3 mm beads for all algae.

    Chapter 4 describes a screening on the applicability of PEF, over a broad range of operating conditions, for the extraction of water soluble proteins from the microalgae C. vulgaris and N. oleoabundans. No substantial protein yields were observed under the investigated conditions. This led to the conclusion that PEF is not suitable to release water soluble proteins, not even at specific energy consumptions much higher than those for the benchmark, bead milling.

    In Chapter 5 it was attempted to improve the performance of PEF by investigating the synergistic effect with the processing temperature. The PEF experiments were performed using a pilot scale continuous flow electroporation unit in which the processing temperature was controlled between 25 – 65 °C. The results showed that under the tested conditions, the combined PEF-Temperature treatment did not cause substantial disintegration of the algal cells to effectively release water soluble proteins.

    In addition to the microalgae, macroalgae were subject of investigation in the search for new protein sources in Chapter 6. Four batch technologies were used to disintegrate the green macroalgae Ulva lactuca, being; osmotic shock, enzyme incubation, PEF and High Shear Homogenization (HSH). In descending order the highest protein yields per treatment; HSH (~40%) > enzyme degradation (~25%) > osmotic shock (~20%) > PEF (~15%).

    In the final chapter the main results and remaining bottlenecks are discussed and a future outlook on microalgae disintegration is presented. To date, bead milling is the only technology able to disintegrate fresh microalgae at specific energy consumptions below 10% of the total energy available from the algae and release substantial amounts of water soluble protein. The future outlook was based on a techno-economic evaluation, which showed that the cultivation costs are limiting the economic feasibility of microalgae biorefinery. Future focus should be on the cultivation.

    Influence of pectin supplementation on feed fermentation characteristics in rats and pigs
    Tian, L. - \ 2016
    Wageningen University. Promotor(en): Harry Gruppen; Henk Schols. - Wageningen : Wageningen University - ISBN 9789462577282 - 142
    pigs - rats - pectins - feed supplements - dietary fibres - digestion - digestive tract - carbohydrates - microbial flora - nutrition physiology - animal nutrition - food chemistry - varkens - ratten - pectinen - voedersupplementen - voedingsvezels - spijsvertering - spijsverteringskanaal - koolhydraten - microbiële flora - voedingsfysiologie - diervoeding - voedselchemie

    The physiological effects of dietary fiber (DFs) depend on several factors including structural features of the DFs, composition and activity of colonic microbiota, and products formed during fermentation. In this thesis, the influence of pectin supplementation to feed fermentation characteristics in rats and pigs was studied. The non-starch polysaccharides (NSP) present in the selected feed ingredient oats were characterized. Distinct populations of arabinoxylans (AXs) were observed in oats, compared to those reported for other cereals like wheat and barley. The fate of cereal AXs and soybean pectin during fermentation and the consequent effects on appetite regulation and fat accumulation were studied in rats as a model. Oat AXs were fermented less rapidly than wheat AXs in the caecum of rats. Soy pectin was fermented more early and efficiently than cereal AXs. A significant inverse correlation between rat retroperitoneal fat-pad weight and concentration and relative SCFA proportion of butyrate was observed. In a following in vivo rat experiment, commercial soy pectin together with three other soluble pectins originating from citrus and sugar beet and differing in their methyl esterification were individually supplemented to the diets. Their effects on the utilization of the different DFs present in the feed and the consequent effect on the microbial community in the colon of rats was studied. All pectins were fermented rapidly and consequently shifted fermentation of other consumed DFs (e.g. cereal AXs) to more distal part of colon, although low-methyl esterified pectin was more efficiently fermented by the microbiota than high-methyl esterified pectin. Results suggested that pectins can confer beneficial health effects through modulation of the gut microbiota. In a last in vivo experiment, citrus pectins together with a hydrothermal treated soybean meal were supplemented to pig diets to study their effect on the digestion and fermentation of carbohydrates in both the small and large intestine. Pectins, and more particularly low-methyl esterified pectin, decreased the ileal digestibility of digestible starch resulting in more starch to be fermentated in the proximal colon of pigs. Consequently, also the fermentation patterns of DFs and the microbiota composition was affected. All pectins tested shaped the colonic microbiota from a Lactobacillus-dominated microbiota to a Prevotella-dominated community, with potential health-promoting effects.

    How mushrooms feed on compost: conversion of carbohydrates and linin in industrial wheat straw based compost enabling the growth of Agaricus bisporus
    Jurak, E. - \ 2015
    Wageningen University. Promotor(en): Harry Gruppen, co-promotor(en): Mirjam Kabel. - Wageningen : Wageningen University - ISBN 9789462573116 - 156
    paddestoelen - champignonmest - koolhydraten - degradatie - substraten - compostering - agaricus bisporus - mushrooms - mushroom compost - carbohydrates - degradation - substrates - composting - agaricus bisporus


    In this thesis, the fate of carbohydrates and lignin was studied in industrial wheat straw based compost during composting and growth of Agaricus bisporus. The aim was to understand the availability and degradability of carbohydrates in order to help improve their utilization in the compost. The wheat straw based compost was characterized as being composed mainly of cellulose and lowly substituted xylan. During the first phase of composting, ester-bound substituents were removed from the xylan backbone and during the second phase of composting 50% of carbohydrates present in the original material where metabolized in a uniform manner. Lignin structure, however, remained unaltered during these composting stages. Over the period of A. bisporus mycelium growth, 20% of the original xylan became water soluble while xylan structures remained rather similar and the remaining water insoluble xylan was partially degraded. In addition, 40% of lignin was metabolized during mycelium growth with an increase in the ratio of syringyl to guaiacyl lignin units from 0.5 to 0.7 in mycelium grown compost compared to the basic compost mixture. During the fruiting body formation minor changes in lignin structure occurred, while accumulation of xylan substituents was observed for arabinosyl residues and glucuronic acid substituents. Finally, putative genes encoding carbohydrate degrading enzymes were identified in A. bisporus’ genome. Genes involved in the pentose and hexose catabolic pathway were found to be upregulated in A. bisporus mycelium. A. bisporus was found to produce both xylan and cellulose degrading enzymes and maximum activity was observed during the formation of the 1st flush of mushrooms. But, as observed from the remaining xylan structures analyzed, A. bisporus lacks the enzymatic activity to degrade xylan substituted with two arabinosyl- residues and glucuronic acid substituted xylan.

    Edita Jurak

    How Mushrooms feed on compost: Conversion of carbohydrates and linin in industrial wheat straw based compost enabling the growth of Agaricus bisporus

    Gestational diabetes mellitus in Tanzania : public health perspectives
    Mwanri, A.W. - \ 2015
    Wageningen University. Promotor(en): Edith Feskens, co-promotor(en): J.L. Kinabo; K. Ramaiya. - Wageningen : Wageningen University - ISBN 9789462572645 - 202
    diabetes mellitus - voedselintolerantie - zwangerschap - zwangerschapscomplicaties - obesitas - koolhydraten - diabetes mellitus - food intolerance - pregnancy - pregnancy complications - obesity - carbohydrates

    Gestational diabetes mellitus in Tanzania – public health perspectives


    Background: Gestational diabetes mellitus (GDM) is defined as carbohydrate intolerance resulting in hyperglycaemia of variable severity with onset or first recognition during pregnancy. Women with GDM are at increased risk for preeclampsia during pregnancy and for delivery complications. In most cases GDM ends after pregnancy, but it increases the risk for future type 2 diabetes, and cardiovascular diseases, to both the mother and the child. With the current increase in prevalence of overweight/obesity and type 2 diabetes in Tanzania and other Sub Saharan African countries, it is possible that GDM may exist and may be on the rise.

    Methods: A cross-sectional survey was done in 2011 through 2013 where 910 women in Tanzania (609 from urban, 301 from rural areas) were studied during their usual antenatal clinic visits. Weight, height, mid upper arm circumference (MUAC), blood pressure and haemoglobin levels were measured by a trained technician. Blood glucose was measured at fasting and at two hours after 75 g oral glucose tolerance test. Women were classified as having GDM using WHO 1999 criteria. Sociodemographic information was collected through face-to-face interviews using structured questionnaire or retrieved from the antenatal clinic card. Dietary intake data was collected using 24-hour recall interview and foods were categorised into groups based on dietary diversity. The international physical activity questionnaire (IPAQ) was used to assess activities in the past one week. Information on birth outcome was obtained from 466 urban mothers (response rate 77%) through telephone interviews. To estimate the burden of GDM in the region, we additionally conducted a systematic search of published literature on the prevalence and risk factors of GDM in Sub Saharan Africa. Out of the 22 reviewed studies, 15 studies graded as having low or moderate risk of bias were included in a meta-regression analysis. Finally, a review of literature regarding the health system and antenatal care was done and supported by a survey to assess antenatal care services in 24 health facilities that provide maternal and childcare services in Dar es Salaam region.

    Results: The prevalence of GDM was much higher among women residing in the urban (8.4%) compared to those in the rural areas (1.0%), which was much higher compared to 0% reported in the 1990s. Prevalence of GDM was higher for women who had a previous stillbirth, family history of type 2 diabetes and MUAC ≥28 cm, and lower for women with normal haemoglobin concentrations compared to those with anaemia. Likewise, the prevalence of hypertension disorders of pregnancy (HDP) was higher in urban (8.9%) compared to rural areas (5.3%). Risk factors for HDP in urban women were advanced maternal age, high MUAC, gestional age and being HIV positive, and in rural women age and gestational age.

    We reviewed 22 studies conducted in six out of the 47 Sub saharan African countries. Heterogeneity between the studies was high and it could not be significantly explained by study setting, population, diagnostic criteria, or the year the study was done. Nevertheless, a relatively higher prevalence was observed in studies done after the year 2000, when women at risk were selected and when more current diagnostic criteria were used. The prevalence was up to about 14.0% when women with at least one risk factor were studied. In Dar es Salaam women, despite a high prevalence of anemia and HIV, the prevalence of macrosomia was higher (5.9%) compared to the prevalence of low birth weight (3.6%). Presence of GDM (OR 3.46, 95% CI 1.01-11.85) and birth weight of the previous child (OR 2.42, 95% CI 1.17-4.99) were the main predictors of macrosomia and HDP (OR 3.75, 95% CI 1.11-12.68) was the main predictor of low birth weight. Although glucose testing in urine appeared to be universally done in the urban setting, the sensitivity of this test for detection of GDM is low. Therefore selective blood glucose testing should be implemented and HIV testing and counselling may be used as an entry point.

    Conclusions: The prevalence of GDM and HDP was higher in the urban compared to the rural areas in Tanzania, indicating an increasing in women who are at risk for delivery complications, poor pregnancy outcomes, type 2 diabetes and cardiovascular diseases in later life. The risk factors observed can be used to identify risk groups for screening and as target for prevention interventions. To inform policy makers and for better health care planning, further studies on the costs for blood glucose testing during the usual antenatal clinic visits and on the management of women with GDM are warranted.

    Koolhydraten bieden scala aan mogelijkheden voor gezonde levensmiddelen
    Schols, H.A. - \ 2014
    Wageningen : Wageningen UR
    voedingsvezels - koolhydraten - voeding en gezondheid - voedingsstoffen - analytische methoden - voedselonderzoek - dietary fibres - carbohydrates - nutrition and health - nutrients - analytical methods - food research
    Koolhydraten in onze voeding leveren energie en zorgen voor een gemakkelijke stoelgang. Van de vele verschillende koolhydraatmoleculen, waaronder tal van soorten kleine suikers, zetmeel en voedingsvezels, weten we echter betrekkelijk weinig. Dat geldt ook voor hun rol tijdens het bewaren en verwerken van levensmiddelen of voor de invloed van koolhydraten op de gezondheid.
    GM1-derived carbohydrates for pathogen and antibody detection : synthesis and biological evaluation
    Garcia Hartjes, J. - \ 2014
    Wageningen University. Promotor(en): Han Zuilhof, co-promotor(en): Tom Wennekes. - Wageningen : Wageningen University - ISBN 9789462571273 - 240
    koolhydraten - moleculaire detectie - antilichamen - pathogenen - remmers - biotesten - carbohydrates - molecular detection - antibodies - pathogens - inhibitors - bioassays
    Dietary carbohydrates and denitrification in recirculating aquaculture systems
    Meriac, A. - \ 2014
    Wageningen University. Promotor(en): Johan Verreth. - Wageningen : Wageningen University - ISBN 9789462570351 - 129
    dieren - vissen - aquacultuur - koolhydraten - denitrificatie - aquacultuur en milieu - feces - vezels - recirculatie aquacultuur systemen - animals - fishes - aquaculture - carbohydrates - denitrification - aquaculture and environment - faeces - fibres - recirculating aquaculture systems

    Due to overfishing of global fish stocks and increasing fish meal prices, plant ingredients are being increasingly used as an alternative source of protein in fish feeds. However, the inclusion of unpurified plant ingredients will also increase the content of fibers in feeds. Fibers are nearly indigestible and will therefore increase solid waste production in aquaculture. This solid waste can be used to as a carbon source for denitrification to control nitrate levels in recirculating aquaculture systems (RAS), thereby reducing both solid and dissolved waste production. Additionally, fibers can change the recovery characteristics and lower the degradability of fecal waste. Therefore, this study investigates how changes in the dietary carbohydrate composition can affect waste production, system performance and denitrification in RAS. Furthermore, ultrasound treatment (to decrease particle size in fecal waste) and enzymatic conditioning (to increase fiber degradability) were tested as possible means to increase the bioavailability of carbon in fecal waste for denitrification.

    Comparing a high fiber (HNSP) and low fiber (LNSP) diet in RAS stocked with rainbow trout confirmed that the fibers in the HNSP diet increase fecal waste production. Although the HNSP diet produced more fecal waste than the LNSP diet, both diets produced the same amount of biodegradable fecal carbon. Since feces removal was higher in RAS using the HNSP diet, the load of degradable organic matter on the biofilters was lower with the HNSP diet than with the LNSP diet. Furthermore, fecal waste produced with the HNSP diet contained larger particles than feces of the LNSP diet, which could also improve the recovery of fecal waste with microscreens. Feces produced with the HNSP diet were also less degradable than feces produced with the LNSP diet. By using fecal waste as an internal carbon source for denitrification, solid and dissolved waste emissions from RAS could be reduced by ~50% for the HNSP diet. However, only approximately half of the supplied cellulose and hemicellulose were degraded in the denitrification reactors, whereas lignin was not degraded at all. Thus, the overall degradability of organic carbon in fecal waste was limited by fibers as hemicellulose, cellulose and lignin. Ultrasound and enzymatic conditioning did not sufficiently increase the degradability of fecal waste. Nonetheless, fibers originating from unpurified plant ingredients may also have beneficial effects on RAS performance by increasing fecal recovery. A more selective choice of feed ingredients could be used to increase the recovery and degradability of fecal waste in RAS.

    Fructan biosynthesis in crop plants : the molecular regulation of fructan biosynthesis in chicory (Cichorium intybus L.)
    Arkel, J. van - \ 2013
    Wageningen University. Promotor(en): Harro Bouwmeester, co-promotor(en): Ingrid van der Meer. - S.l. : s.n. - ISBN 9789461736635 - 158
    cichorium intybus - gewassen - zea mays - solanum tuberosum - transgene planten - koolhydraten - fructanen - biosynthese - inuline - polymerisatie - cichorium intybus - crops - zea mays - solanum tuberosum - transgenic plants - carbohydrates - fructans - biosynthesis - inulin - polymerization

    Fructan is a polymer of fructose produced by plants and microorganisms. Within the plant kingdom about 45.000 species accumulate fructan as storage carbohydrate in addition to, or instead of, starch. Fructan accumulating species are mainly found in temperate and sub-tropical regions with seasonal or sporadic rainfall. During the last decades, the use of fructan in the (food) industry has rapidly evolved, because of its health promoting characteristics and interesting functional properties.Chicory (Cichorium intybus L.) is a biennial taproot-bearing crop plant that is grown for the production of inulin on an industrial scale. Inulin, a ß(2,1) linked linear fructan with a terminal glucose residue, is stored in the chicory taproots. The degree of polymerisation (DP) determines the application of the inulin and hence the value of the crop. This leads us to the central question of this thesis:

    What regulates the fructan yield and the degree of polymerisation, and how can we modify this?

    The DP is highly dependent on the field conditions and harvest time, and therefore the first step in answering this question was tostudy the regulation of fructan (inulin) metabolism throughout the growing season. This is described in Chapter 2. Metabolic aspects of inulin production and degradation in chicory were monitored in the field and under controlled conditions. We determined the concentrations of soluble carbohydrates, the inulin mean degree of polymerisation (mDP), inulin yield, gene expression and activity of enzymes involved in inulin metabolism in the taproots. Inulin biosynthesis - catalysed by sucrose: sucrose 1-fructosyltransferase (EC (1-SST) and fructan: fructan 1-fructosyltransferase (EC (1-FFT) - started at the onset of taproot development. Inulin yield increased with time following a sigmoid curve reaching a maximum in November. The maximum inulin mDP of 15 was reached in September and then gradually decreased. Based on the changes observed in the pattern of inulin accumulation, we defined three phases in the growing season and analysed product formation, enzyme activity and gene expression in these defined periods. The results were validated by performing experiments under controlled conditions in climate rooms. Our results show that the decrease in 1-SST is not regulated by day length and temperature. From mid-September onwards the mDP decreased gradually although inulin yield still increased. This is most probably the result from back-transfer activity of 1-FFT and fructan exohydrolase activity (EC (1-FEH). In plants 1-FEH catalyses the breakdown of fructan in order to release the stored carbohydrates necessary in periods of stress, like cold or drought periodsor flowering. This information was used to design two strategies to obtain the desired, increased inulin DP and yield. Overexpression of 1-SSTwas performed to increase the mDP and to keep the sucrose concentration low, to prevent 1-FFT from depolymerizing inulin. The result was a higher mDP during the growing season. Unfortunately, no effect on the mDP was seen at the end of the growing season, most probably due to activity of FEH. Secondly, anFEH I antisense fragment was introduced into chicory in order to block depolymerisation at the end of the growing season. This resulted in a reduction in FEH Iexpression upon cold induction, but had only minor effects on the mDP. The degradation of inulin was most probably caused by the remaining 1-FEH activity. Overall this study showed that inulin metabolism in chicory is tightly regulated, but also revealed options to further steer inulin metabolism in chicory.

    The next step in answering the central question was to study the regulation of the genes involved in fructan biosynthesis. In Chapter 3this was studied at three different levels. Firstly, fructan gene expression and carbohydrate concentrations were studied in axial sections of mature chicory root, revealing the highest expression levels and carbohydrate levels in the phloem. Correlations were found between the gene expression patterns of 1-SST, 1-FFT and the carbohydrate levels, suggesting a possible involvement of sugars in the regulation of 1-SSTand 1-FFTgene expression. Secondly, the induction of 1-SSTand 1-FFTexpression was studied in excised chicory leaves. Expression of both 1-SSTand 1-FFTwas induced upon sucrose and glucose feeding, suggesting that both genes are at least partly regulated in the same way. Upon fructose feeding, the induction of fructan biosynthesis was less pronounced than with sucrose. The expression of 1-SSTwas induced by fructose but this resulted in only low amounts of 1-kestose. The expression of 1-FFTwas not induced upon fructose feeding.Thirdly, to further unravel the mechanism of induction, the promoters of 1-SSTand 1-FFTfrom chicory were isolated and characterized through in silicoand in planta(only 1-FFT) analysis. Computational analysis of fructosyltransferase (FT) promoters revealed elements that are common in fructan biosynthesis-promoters among different species and also occur in Arabidopsis promoter sequences. One of these elements is predominantly present in genes involved in sugar metabolism and transport. This element did also contain a core sequence involved in MYB transcription factor binding important for fructan biosynthesis activation in wheat, as was published recently. An 1100bp 1-FFTpromoter fragment was shown to be functional in transgenic chicory and in the non-fructan accumulating plants species, Arabidopsis and potato. Application of carbohydrates resulted in the expression of the reporter gene GUS comparable to 1-FFTexpression upon carbohydrate feeding in chicory. This study provides information on the regulation of inulin biosynthesis, suggestions for studies on transcription factors, and provides a promoter for steering the expression of fructan biosynthetic genes in transgenic plants. An alternative way for the production of inulin with the desired DP and yield, circumventing the problems in chicory rather than trying to solve them, is the introduction of the fructan biosynthetic pathway in non-fructan metabolizing and catabolizing plant species.

    Towards this end we have expressed the inulin synthesizing enzymes, 1-SST and 1-FFT from Jerusalem artichoke, in maize and potato, as described inChapter 4. Transgenic maize plants produced inulin type fructan (at 3.2 milligram per gram kernel) and kernel development was not affected. Potato tubers expressing 1-SSTaccumulated 1.8 milligram inulin per gram tuber while tubers with a combined expression of 1-SSTand 1-FFTaccumulated 2.6 milligram inulin per gram tuber. Inulin accumulation in maize kernels was modulated by kernel development, first peaking in young seeds and then decreasing again through degradation during late kernel development. In potato, inulin mDP was relatively stable throughout tuber development and little evidence of degradation was observed. The accumulation of 1-kestose in transgenic maize correlated positively with kernel sucrose concentration and introduction of the fructan biosynthetic pathway in a high-sucrose maize background increased inulin accumulation to 41 milligram per gram kernel kernel. This study shows the importance of sugar availability and the absence of degradation mechanisms in platform crops for tailor-made fructan production.

    Further evaluation of the production of tailor-made inulin and putative platform crops is discussed in Chapter5.Here we come to the conclusion that the mDP, the distribution and yield depend on the origin of the fructan biosynthesis genes and the availability of sucrose in the host. The combination of genes from different origins could result in new types and different lengths of fructan molecules resulting in (new) specific properties of fructan. Limitations for the production of tailor-made fructan in chicory are not seen in putative new platform crops, such as sugar beet, sugarcane and rice.

    The work described in this thesis on fructan biosynthesis in chicory and in new platform crops has resulted in new insights that will lead new applied and fundamental research in this field.

    Physiological ecology of the frankincense tree
    Mengistu Woldie, T. - \ 2011
    Wageningen University. Promotor(en): Frans Bongers; G. Fetene, co-promotor(en): Frank Sterck. - S.l. : s.n. - ISBN 9789085859277 - 127
    boswellia - koolstof - ecologie - plantenfysiologie - tappen (rubber) - bosgebieden - koolhydraten - bladoppervlakte - bomen - harsen - harswinning - ethiopië - boswellia - carbon - ecology - plant physiology - tapping - woodlands - carbohydrates - leaf area - trees - resins - resin extraction - ethiopia

    Keywords: Boswellia papyrifera, carbon balance, drylands, Ethiopia, frankincense, tapping

    The degradation of frankincense tree dominated woodlands has been attributed to climatic
    conditions and human activities. We lack however information on how such factors influence the
    resource balance and productivity of trees. The aim of this study was to evaluate the impact of
    resin tapping on the whole tree carbon gain, storage and allocation pattern of frankincense trees
    (Boswellia papyrifera (Del.) Hochst) in the dry woodlands of northern Ethiopia. I hypothesized
    that the intensive resin tapping of frankincense trees reduces tree vitality, particularly under
    relatively dry conditions. I established experimental plots in the highland woodlands of
    Abergelle and the lowland woodlands of Metema, and applied tapping treatments to similar sized
    adult trees (DBH 20 +/- 3cm). For these trees I also collected data on leaf gas exchange, crown
    traits, carbon storage, carbon allocation, growth and frankincense production during a period of
    two years (2008-2009).
    Trees follow similar leaf gas exchange patterns in contrasting environments, but differ in
    annual crown carbon gain between highland and lowland sites. Highland trees of Boswellia had a
    higher photosynthetic capacity, were exposed to higher light conditions, but had a shorter leaf
    lifespan than lowland trees. Integrating these effects, I showed that the annual crown carbon gain
    is higher in the highland trees than in lowland trees. Lowland trees are mainly constrained by
    clouded conditions and resultant low light levels during the wet season, limiting their carbon
    gain. Moreover, carbon gain was also restricted by atmospheric drought, and much less by soil
    water deficit during the growing season. The production of frankincense was not affected by the
    annual tree carbon gain implying that trees with smaller total leaf area may suffer sooner from
    carbon starvation by tapping.
    Tapping reduced storage carbohydrate concentrations in wood, bark and root tissues
    indicating that continuous tapping depletes the carbon reserves. A large part of the carbohydrate
    concentration in the plant tissues was starch. Boswellia trees have more total nonstructural
    carbohydrates (TNC) concentrations and pool sizes in wood than in root and bark tissues.
    Because tapped trees face depleting carbon storage pools during the dry tapping season and
    cannot fully replenish these pools during the wet season, tapped trees may face higher risks of
    carbon starvation compared to untapped trees in the long term.
    Estimated total annual carbon sinks to the different plant components were 38-68% of the
    annual carbon gain in both study sites. However, Boswellia trees also establish mycorrhizal
    associations which may consume an additional 20% of gross primary production. On a wholetree
    basis, the percentage of autotrophic respiration may exceed all other costs. The foliage
    construction costs and incense production are the second and third largest carbon sinks,
    respectively. Contrary to our expectation, the sum of all dry season carbon costs was higher than
    the total amount of consumed TNC during the dry season. The high carbon costs during the dry
    season imply that trees do not fully depend on TNC to pay for the carbon costs during the dry
    season. With the exception of carbon allocation to foliage production and maintenance, a higher
    gross primary production does not enhance an overall increase in carbohydrate investments in
    the other sinks. Therefore, the carbon allocation pattern is constrained not exclusively by the
    absolute amount of carbon gained but also by other factors.
    The results clearly indicate that continuous tapping depletes the amount of stored carbon,
    the leaf area production and the reproductive effort. These negative effects were however site
    specific and could possibly be apparent sooner for smaller trees than for larger ones. Thus,
    guidelines for resin tapping of Boswellia trees should consider tapping intensity, tapping
    frequency, environmental conditions and tree size and should focus on maintaining vital trees
    and populations for the future.

    Background information and biorefinery status, potential and Sustainability: Task 2.1.2 Market and Consumers; Carbohydrates
    Bos, H.L. ; Harmsen, P.F.H. ; Annevelink, E. - \ 2010
    Wageningen : Wageningen UR - Food & Biobased Research (Star-Colibri Deliverable 2.1.2) - 28
    koolhydraten - markten - biobased economy - chemie op basis van biologische grondstoffen - biopolymeren - bioraffinage - reststromen - coproductie - carbohydrates - markets - biobased economy - biobased chemistry - biopolymers - biorefinery - residual streams - coproduction
    This report was produced to give an overview of present and future market for biorefinery products based on carbohydrates. Various studies show that there is a wealth of possible molecules and products that can be produced from carbohydrates. Carbohydrates already find significant application in starch products and cellulose plastics and fibres. However, for a biorefinery to operate in an economically sustainable way, applications for (preferably all) biomass ingredients need to be found. Presumably the optimal mix of applications will be a combination of larger volume/smaller value and smaller volume/higher value applications. For this study we therefore have taken a molecular approach. Looking at the size of possible end markets for the molecules that can be based on carbohydrates a number of main products come into view: dialcohols, dioic acids, 2,5 furan dicarboxylic acid and ethanol. These molecules with a wide application range can serve as basis targets for the carbohydrate stream of a biorefinery, provided the production processes are optimised to make them competitive to the petrochemical counterparts. Speciality applications for the resulting side streams will then need to be found on a case by case basis.
    Plant - Microbiele Brandstofcel (MFC): exudate productie : het optimaliseren van wortelexudatie met een split-root systeem
    Khodabaks, M. ; Blok, C. ; Berg, C.C. van den; Snel, J.F.H. - \ 2009
    Bleiswijk : Wageningen UR Greenhouse Horticulture - 13
    akkerbouw- en tuinbouwbedrijven - kassen - exudaten - wortelexudaten - secreties - aminozuren - organische zuren - micro-organismen - organische stof - suikers - koolhydraten - teelt onder bescherming - microbiële brandstofcellen - glastuinbouw - biobased economy - crop enterprises - greenhouses - exudates - root exudates - secretions - amino acids - organic acids - microorganisms - organic matter - sugars - carbohydrates - protected cultivation - microbial fuel cells - greenhouse horticulture
    De plant microbiële brandstofcel of Plant Microbial Fuel Cell (Plant$MFC) is een technologie die het op basis van een nieuw principe mogelijk maakt direct elektriciteit of biofuels aan een plant te onttrekken, zonder dat deze geoogst hoeft te worden (Strik en Helderman, 2004). Levende planten zetten door fotosynthese zonne-energie om in energiehoudende biomassa zoals eiwitten, suikers, zetmeel, cellulose en ligine. Van de netto vastgelegde koolstof wordt doorgaans een fractie van 40 tot 60 % naar de wortels getransporteerd. Van de hoeveelheid koolstof getransporteerd naar het wortelstelsel wordt door planten een fractie van 50 tot 70 % uitgescheiden naar de bodem in oplosbare vorm (exudaten en secreties). Deze exudaten en secreties bestaan onder andere uit suikers, aminozuren, organische zuren en koolhydraten welke gemakkelijk door micro-organismen kunnen worden omgezet. De uitgescheiden organische stof kan deels door natuurlijk voorkomende micro-organismen worden omzet in electriciteit. Als deze electriciteit in de een of ander vorm wordt opgevangen en benut is sprake van een MFC. In een MFC is het zaak het aandeel en de activiteit van de electriciteit producerende micro-organismen hoog te maken en te houden
    Schimmels veroorzaken merendeel van de plantenziekten : voortdurende wapenwedloop tussen plant en schimmel
    Kierkels, T. ; Heuvelink, E. - \ 2008
    Onder Glas 5 (2008)3. - p. 4 - 5.
    schimmel - plantenziekteverwekkende schimmels - koolhydraten - assimilatie - ziekteresistentie - antagonisten - ondersteunende maatregelen - gewasbescherming - glastuinbouw - moulds - plant pathogenic fungi - carbohydrates - assimilation - disease resistance - antagonists - support measures - plant protection - greenhouse horticulture
    Schimmels kunnen niet zelf assimileren en maken daarom gebruik van dat vermogen van planten. Cruciaal is dat ze planten moeten binnendringen om bij de koolhydraten te kunnen komen. Daartoe hebben ze tal van manieren ontwikkeld, mechanisch en chemisch. De plant op zijn beurt zet blokkades en chemie in om de schimmels te weren. Een goed groeiende, gezonde plant is in het algemeen weerbaar genoeg. Inzicht in de 'wapenwedloop' tussen schimmel en plant wijst een teler de weg naar ondersteunende maatregelen
    Onderzoek moet uniformer stek bij siergewassen opleveren (o.a. interview met Hendrik-Jan van Telgen)
    Staalduinen, J. van; Telgen, H.J. van - \ 2007
    Onder Glas 4 (2007)8. - p. 54 - 55.
    siergewassen - rozen - potplanten - vermeerderingsmateriaal - stekken - fotosynthese - meting - technieken - koolhydraten - beworteling - onderzoek - glastuinbouw - snijbloemen - ornamental crops - roses - pot plants - propagation materials - cuttings - photosynthesis - measurement - techniques - carbohydrates - rooting - research - greenhouse horticulture - cut flowers
    Het slagingspercentage en de uniformiteit van stekken worden mede bepaald door inwendige factoren, zoals fotosynthesecapaciteit en de koolhydraatstatus in het blad. Met behulp van diverse meettechnieken onderzoekt een projectteam of op basis van de gemeten waarden voorspellingen mogelijk zijn over de mate van beworteling en uitgroei. Als dat zo is, kunnen deze technieken bijdragen aan optimalisatie van de bedrijfsprocessen op vermeerderingsbedrijven
    Het effect van voersamenstelling op bacteriële darmaandoeningen bij varkens = The effect of feed composition on bacterial intestinal diseases in pigs
    Meulen, J. van der; Peet-Schwering, C.M.C. van der - \ 2007
    Lelystad : Animal Sciences Group (Rapport / Animal Sciences Group, Divisie Veehouderij 83) - 14
    varkens - dierhouderij - diervoeding - voersamenstelling - koolhydraten - darmziekten - diergezondheid - bacterieziekten - dysenterie - varkensdysenterie - colitis - enteritis - salmonellose - pigs - animal husbandry - animal nutrition - feed formulation - carbohydrates - intestinal diseases - animal health - bacterial diseases - dysentery - swine dysentery - colitis - enteritis - salmonellosis
    Feed composition, and especially carbohydrate composition, may affect the development of enteric bacterial diseases. Also the kind of feed ingredients (soybean or not) and feed treatment (milling size, pelletizing, fermentation) may be important. A more coarse grinding, no pelletizing and fermentation may be preferable in the reduction of the development of enteric bacterial diseases.
    Chemical composition of lamina and sheath of Lolium perenne as affected by herbage management
    Hoekstra, N.J. ; Struik, P.C. ; Lantinga, E.A. ; Schulte, R.P.O. - \ 2007
    NJAS Wageningen Journal of Life Sciences 55 (2007)1. - ISSN 1573-5214 - p. 55 - 73.
    afsnijhoogte - grasbestand - voedergewassen - lolium perenne - hergroei - rotaties - chemische samenstelling - graslandbeheer - voedingswaarde - lignine - totale hoeveelheid droge stof - koolhydraten - stikstof - vezelgehalte - bloeiwijzen - cutting height - herbage - fodder crops - lolium perenne - regrowth - rotations - chemical composition - grassland management - nutritive value - lignin - total solids - carbohydrates - nitrogen - fibre content - inflorescences - water-soluble carbohydrate - neutral detergent fiber - dairy-cows - nitrogen application - nutritive-value - ryegrass varieties - animal nutrition - milk-production - rumen function - l. cultivars
    The quality of grass in terms of form and relative amounts of energy and protein affects both animal production per unit of intake and nitrogen (N) utilization. Quality can be manipulated by herbage management and choice of cultivar. The effects of N application rate (0, 90 or 390 kg N ha¿1 year¿1), duration of regrowth period (2¿3, 4¿5, or 6¿7 weeks), and cutting height (8 or 12 cm) on the mass fractions of nitrogen (N), water-soluble carbohydrates (WSC), neutral detergent fibre (NDF), acid detergent fibre (ADF), lignin and ash in lamina and sheath material of a high-sugar (Aberdart) and a low-sugar (Respect) perennial ryegrass (Lolium perenne) cultivar, were studied in a factorial field experiment during four seasons in 2002 and 2003. Expressing NDF and ADF mass fractions in g per kg WSC-free dry matter (DM) increased the consistency of treatment effects. The high-sugar cultivar had generally higher WSC mass fractions than the low-sugar cultivar, especially during the late season. Moreover, the relative difference in WSC mass fraction between the two cultivars tended to be higher for the lamina material than for the sheath material, which suggests that the high-sugar trait may be more important under grazing conditions, when lamina forms the bulk of the intake, than under mowing regimes. Longer regrowth periods and lower N application rates increased WSC mass fractions and decreased N mass fractions; interactions between regrowth period and N application rate were highly significant. The mass fractions of NDF and ADF were much less influenced. The NDF mass fraction in terms of g per kg WSC-free DM tended to be higher at lower N application rates and at longer regrowth periods. The effect of cutting height on herbage chemical composition was unclear. In conclusion, high-sugar cultivars, N application rate and length of the regrowth period are important tools for manipulating herbage quality.
    Rumen development in veal (preruminant) calves
    Suárez, B.J. - \ 2006
    Wageningen University. Promotor(en): Seerp Tamminga, co-promotor(en): Walter Gerrits; Jan Dijkstra. - [S.l.] : S.n. - ISBN 9789085045366 - 174
    vleeskalveren - pensontwikkeling - pensfermentatie - concentraten - ruwvoer (roughage) - voer - samenstelling - koolhydraten - enzymactiviteit - mestresultaten - kalvervoeding - veal calves - rumen development - rumen fermentation - concentrates - roughage - feeds - composition - carbohydrates - enzyme activity - fattening performance - calf feeding
    Historically, veal calves were fed until slaughter weight with only milk replacer and, in absence of solid feed the physiological development of the forestomachs was limited. In 1997, a new EU legislation stipulated that a minimum amount of solid feed (fiber) has to be provided for the welfare of the calves (solid feed supply reduce abnormal oral behaviors in veal calves; Van Putten, 1982; Veissier et al., 1998); however, no specifications were made about the type and source of feed.

    Rumen development is triggered by the production of VFA resulting from fermentation ofOMin the rumen (Flatt et al., 1958). Butyrate, and to a lesser extent propionate stimulate the development of the rumen mucosa; mostly because of their use as energy sources by the rumen epithelium (Sander et al., 1959; Tamate et al., 1962). In rearing calves, information on rumen fermentation of different sources of dietary carbohydrates is relatively well documented (Davis and Drackley, 1998; Lesmeister and Heinrichs, 2004) but only a few experiments have been conducted in veal calves.

    Based on earlier research (Blokhuis et al., 2000) it was hypothesized that stimulating early rumen development in veal calves would be beneficial to their subsequent performance and health. Therefore in vivo experiments were designed to establish the effects of stimulating an early rumen development in veal calves, aiming to optimize nutrient utilization from rumen fermentation and to prevent health problems in the lower gastrointestinal tract (e.g. ulcers in abomasum). In addition the potential interactions of feeding solid feed with a milk replacer based diet were investigated. Finally but not least, the development and evaluation (comparison) of techniques for estimating fermentation characteristics of different substrates, to facilitate the choice of feed ingredient for veal calves diets was also carried out. 

    Chapter 2:This study was conducted to evaluate the effects of concentrate intake, differing in carbohydrates composition in addition to a milk replacer, on growth performance and rumen fermentation characteristics in veal calves. Accordingly, 160 Holstein Friesian x Dutch Friesian male calves, were fed with one of the following treatments: 1) milk replacer control (CONTROL), 2) pectin-based concentrate (PECTIN), 3) neutral detergent fiber (NDF) based concentrate, 4) starch-based concentrate (STARCH) and 5) mixed concentrate (MIXED) (equal amounts of concentrates of treatments 2, 3, and 4). Concentrate diets were provided in addition to a commercial milk replacer Results: Calves showed an ADG varying between 0.70 and 0.78 kg/d, with a rumen fermentation in concentrates fed calves characterized by a low pH (4.9 - 5.2), relatively low VFA concentrations between 100 and 121 mmol/L and high concentrations of reducing sugars (33-66 g/kg DM). Calves fed the CONTROL diet had higher lactate concentration (21mmol/L) than concentrate fed calves (between 5 and 11 mmol/L). Results indicated that the carbohydrate source can influence intake, growth rate and rumen fermentation in young veal calves.

    Chapter 3:This experiment aimed to gain an insight into the effects of age (calves were euthanized either at the end of 8 or 12 weeks of age) and concentrate supplementation, differing in carbohydrates composition, on rumen development in young veal calves. Moreover, some selected plasma metabolites as predictors of rumen development were evaluated. Diets treatments correspond to those described in Chapter 2. Results: Feeding concentrates differing in carbohydrate composition to veal calves promoted rumen development compared with calves fed milk replacer only. In most calves, a poorly developed rumen mucosa was observed. Coalescing rumen papillae with embedded hair, feed particles and cell debris were found in all calves fed concentrate diets. Calves fed concentrates had significantly heavier rumens than calves fed CONTROL. Although the variation in carbohydrate composition caused variation in rumen development, the latter was generally small. In the dorsal location of the rumen, calves fed concentrate diets showed an increased ratio of mucosa to serosa length (RMSL) than calves fed CONTROL. Mucosa thickness (MCT) and muscle thickness (MST) were bigger in the ventral and in the dorsal locations of the rumen, respectively.

    At 8 weeks, calves fed concentrate diets had higher plasma acetate concentrations than calves on the CONTROL treatment. However, at 12 weeks, only NDF fed calves showed significantly higher plasma acetate concentrations. For plasma BHBA concentration no differences were observed among treatments at 12 weeks. Results from a principal component analysis indicated that veal calves, in addition to rumen volatile fatty acids (VFA) concentrations, other factors are likely to affect rumen development.  

    Chapter 4:This experiment was designed based on the results obtained in experiment 1 (Chapter 2 and 3) where in concentrate-fed veal calves a rumen environment, characterized by a sub clinical acidosis (pH< 5.2), relatively low VFA concentrations (100-120 mmol/L) and a rumen mucosa characterized by poorly shaped papillae with feed and cell debris embedded between them (referred as plaque formation) were observed. Feeding only roughage to young calves generally does not promote rapid papillae development (Nocek and Kesler, 1980); however, roughage consumption and its inherent coarseness stimulate the development of the rumen wall (Tamate et al., 1962) and rumination (Hodgson, 1971) and the healthiness of the rumen mucosa (Haskins et al., 1969). Information concerning the effects of roughage intake on veal calves performance and rumen development is scarce (Blokhuis et al., 2000; Cozzi et al., 2002). Therefore, it was hypothesized that adding small amount of roughage to a concentrate diet will improve and stimulates the development of the rumen wall, without having negative effects on calf's performance. Sixty four male Holstein Friesian x Dutch Friesian veal calves (46 kg ± 3.0 kg), were fed on of the following diets: 1) C100= concentrate only, 2) C70-S30= concentrate (70%) with straw (30%), 3) C70-G30= concentrate (70%) with dried grass (30%), 4) C70-G15-S15= concentrate (70%) with dried grass (15%) and straw (15%), 5) C70-CS30= concentrate (70%) with corn silage (30%), 6) C40-CS60= concentrate (40%) with corn silage (60%), 7) C70-CS30-AL= concentrate (70%) with corn silage (30%) ad libitum, 8) C70-G15-S15-AL= concentrate (70%) with dried grass (15%) and straw (15%) ad libitum. All dietary treatments were provided in addition to a commercial milk replacer. Concentrate was provided as pellets and roughage was chopped. Results: Roughage and intake level affects rumen fermentation and rumen development of veal calves. Substitution of part of the concentrate by roughage did not affect DMI and ADG, but among roughage sources feeding straw reduced DMI and ADG. The addition of roughage did not affect rumen pH (pH >5.3). Rumen fermentation was characterized by high total volatile fatty acids (VFA) and reducing sugars (RS) concentrations. Cobalt recovery, as an indication of milk leakage was found in the rumen, varying between 20.5 and 34.9 %, but it was not affected by dietary treatments. Roughage addition decreased the incidence of plaque formation and the incidence of calves with poorly developed rumen mucosa. However, morphometric parameters of the rumen wall were hardly influenced by the type and level of roughage. Results indicated that in veal calves, the addition of roughage to concentrate diets did not affect growth performance and positively influenced the macroscopic appearance of the rumen wall.

    Chapter 5:Several methodologies have been developed to characterize feedstuffs in terms of digestibility and degradability, comprising in vivo , in situ and in vitro methods.

    The gas production technique (GPT) provides gas production profiles that give an indication of the fermentative characteristics of the feed. The objective of this experiment was to estimate fermentation kinetic parameters of various solid feeds supplied to veal calves using the GPT, and to study the effect of adaptation of the rumen microflora to these solid feeds on their subsequent fermentation patterns. Thus, from the in vivo experiment described in Chapter 2 and 3; three out of five dietary treatments were selected as inoculum sources: pectin ( PECTIN ), neutral detergent fiber ( NDF ), and starch ( STARCH ). Sugar beet pulp ( SBP ), sugar beet pectin ( SBPec) , native corn starch ( NCS ), soy bean hulls ( SBH ) and crystalline cellulose ( AVICEL) were selected as substrates. For the second in vitro experiment, three out of eight dietary treatments (from the in vivo experiment described in Chapter 4) were selected as inocula. The selected diet treatments were: C100= concentrate only, C70-S30 = concentrate (70%) with straw (30%) and C70-CS30 = concentrate (70%) with corn silage (30%). For this gas production experiment, straw ( STRAW ), soy bean hulls ( SBH ), native corn starch ( NCS ) and sugar beet pectin ( SBPec ) were chosen as in vitro substrates.

    For both in vivo experiments, cumulative gas production was measured over time (72 h) as an indicator of the kinetics of fermentation. Fermentation end-products, including volatile fatty acids and ammonia, and organic matter loss, were also measured. Results : In both experiments significant differences between the inoculum sources, in terms of both fermentation kinetics characteristics and end-products of fermentation were observed. Similarly, significant effects were also observed for substrate compositions. Differences between the fermentation characteristics of NCS, SBPec and SBH, were consistent for both experiments. The total VFA production was not different among these substrates in both experiments. Finally, for both experiments, there was a significant inocula and substrate interaction which may indicate differences in the microbial activity occurring between the calves. Therefore, it was concluded that rumen inoculum from adapted animals should be used to obtain a more accurate assessment of feed ingredients in veal calf diets.

    Chapter 6 (General discussion) focused in four points: a) Factors influencing rumen development in rearing and veal calves; b) The importance of ruminal drinking in veal calves fed solids feeds; c) Effects of feeding strategies on ruminal pH and buffering capacity of rumen contents in veal calves; d) comparative analysis of the results obtained from the GPT (results presented in Chapter 5) and the PDE activities (results presented in Chapter 2 and 4).
    Limiting factors for the enzymatic accessibility of soybean protein
    Fischer, M. - \ 2006
    Wageningen University. Promotor(en): Harry Gruppen; Fons Voragen. - [S.l.] : S.n. - ISBN 9789085044963 - 139
    sojaeiwit - hydrolyse - aggregatie - koolhydraten - eiwitextractie - eiwitvertering - eiwitverteerbaarheid - peptiden - soya protein - hydrolysis - aggregation - carbohydrates - protein extraction - protein digestion - protein digestibility - peptides
    Soy is a commonly used ingredient is food and animal feed. With particular focus on the in-soluble fractions, this thesis deals with the effects of proteases and carbohydrate degrading enzymes on different soybean meals subjected to different extent of heating. The primary aim is to improve the understanding of enzymatic hydrolysis of SBM with emphasis on proteins and to identify barriers limiting the efficiency of the process. The results show that aggregation behavior of peptides during enzymatic processing of soy proteins is potentially a limiting factor for efficacy of protein extraction. Surprisingly, it is also demonstrated that aggregation is not limited to in vitro incubations, but is also occurring in vivo in the digestive system of pigs.
    Prebiotics in piglet nutrition? Fermentation kinetics along the GI tract
    Awati, A.A. - \ 2005
    Wageningen University. Promotor(en): Martin Verstegen, co-promotor(en): B.A. Williams; M.W. Bosch. - Wageningen : S.n. - ISBN 9789085041641 - 143
    biggen - anti-infectieuze middelen - koolhydraten - fermentatie - kinetica - voedertoevoegingen - microbiële ecologie - varkensvoeding - voedingsfysiologie - piglets - antiinfective agents - carbohydrates - fermentation - kinetics - feed additives - microbial ecology - pig feeding - nutrition physiology

    Keywords: fermentation, gas production, piglets

    The generalized theory behind the carbohydrate to protein fermentation in the GIT is that in presence of fermentable carbohydrate substrate, microbes prefer to ferment carbohydrate source to derive energy and use the nitrogen available for their own growth. With this background information, it was hypothesized that inclusion of fermentable carbohydrates in the piglet diet will reduce the protein fermentation, which will be confirmed by reduced levels of ammonia and branched chain fatty acids in end product profile of the fermentation. The aim of this thesis was to study the effects of inclusion of fermentable carbohydrates in weaning piglets' diet, on GIT fermentation and any changes in microbial community composition and activity. Weaning process in an intensified pig production system brings many sudden changes in the environmental and physical factors in piglets' life. These sudden changes, especially in diet cause serious imbalance in the microbial community. Quicker stabilization and diversification of microbial community post weaning, is crucial in attending the gut health and reducing the risk of pathogenic infections by 'Colonization resistance: As part of this overall aim, the in vitro cumulative gas production technique was used to study the fermentation of selected fermentable substrates. While these substrates namely lactulose, inulin, wheat starch and sugar beet pulp (SBP) were included in test diet and their effect on GIT fermentation was studied in vivo. The combination of microbial community analysis based on fingerprinting techniques such as denaturing gradient gel electrophoresis (DGGE) with nutritional analysis of fermentation end product profiles, was used in vivo and in vitro studies. In in vivo trials, emphasis was given on using combination of slow fermenting carbohydrate sources such as, SBP and wheat starch with fast fermenting lactulose and inulin. The hypothesis behind this approach was to induce carbohydrate fermentation along the GIT, by providing carbohydrate substrate for the microbiota in different parts of GIT. Especially by taking in to account the difference in the transit time of feed in the different parts of GIT, it was expected that fast fermenting lactulose and inulin would be fermented in small intestine while wheat starch somewhere in the beginning of the large intestine while, SBP will reach the distal part of colon. It was found that fermentation along the GIT was improved or in other words skewed more towards the carbohydrate fermentation in vivo. It was observed in vivo that inclusion of fermentable carbohydrates in the diet reduces the protein fermentation in the GIT and ammonia concentration in end product profile. This decrease was observed along the GIT and in time in faecal fermentation end product profiles post weaning. Microbial community analysis using fingerprinting techniques revealed that inclusion of fermentable carbohydrates stabilized and diversified microbial community in the ileum as well as in the colon by day 10 post weaning. This way, the prebiotic effects of fermentable carbohydrates was evidenced. -
    Effects of prebiotics, probiotics and synbiotics in the diet of young pigs
    Shim, S.B. - \ 2005
    Wageningen University. Promotor(en): Martin Verstegen, co-promotor(en): J.M.A.J. Verdonk. - s.l. : S.n. - ISBN 9789085041931 - 178
    biggen - probiotica - koolhydraten - anti-infectieuze middelen - voedertoevoegingen - microbiële ecologie - fermentatie - spijsverteringsstelsel - varkensvoeding - voer - diergezondheid - groei - voedingsfysiologie - piglets - probiotics - carbohydrates - antiinfective agents - feed additives - microbial ecology - fermentation - digestive system - pig feeding - feeds - animal health - growth - nutrition physiology

    Keywords: prebiotics, piglets, gut health
    Prebiotics are non-digestible carbohydrates that are not metabolized in the small intestine and fermented in the large intestine. Oligofructose are non-digestible oligosaccharides which may stimulate beneficial bacteria in the gut and may affect the gut ecosystem. Prebiotic effects will depend largely on their chemical structure (degree of polymerization). Dietary inclusion of probiotics in young pig diets may beneficially affect gut microbiota. Synbiotics, a combination of prebiotics and probiotics may also stimulate the gut ecosystem. The objective of this thesis was to evaluate the effects of pre-, pro- and synbiotics on the gut ecosystem, and some performance parameters. A series of in vivo and in vitro experiments were carried out using suckling and weaned piglets. The experimental results are discussed in this thesis. Overall, it was concluded that synbiotics, a combination of multi-strain probiotics and oligofructose, can positively affect performance especially feed intake, and can improve the gut health. However, we did not observe a clear synergistic effect compared to supplementing oligofructose or probiotics alone. A combination of high and low polymer inulin will probably be more beneficial for the intestinal ecosystem and health than using either high- or low polymer inulin alone. The present studies show that the pre-, pro- and synbiotic treatments affect gut microbiota and performance of young pigs.
    Vitaliteit van Freesiaknollen: opsporen van kritische factoren voor de vitaliteit van freesiaknollen in verband met heterogeniteit in de oogstfase
    Heij, G. ; Kersten, M. ; Slootweg, G. - \ 2004
    Naaldwijk : Praktijkonderzoek Plant & Omgeving B.V. (Rapport PPO ) - 21
    freesia - bloembollen - teelt onder bescherming - plantenontwikkeling - groeifasen, rijp - bollen - selectie - kwaliteit - planttijd - koolhydraten - nederland - freesia - ornamental bulbs - protected cultivation - plant development - maturity stage - bulbs - selection - quality - planting date - carbohydrates - netherlands
    Gastrointestinal Health Benefits of Soy Water-soluble Carbohydrates in Young Broiler Chickens
    Lan, Y. - \ 2004
    Wageningen University. Promotor(en): Martin Verstegen; Seerp Tamminga; G. Erdi, co-promotor(en): B.A. Williams. - [S.I.] : S.n. - ISBN 9789064649240 - 265
    vleeskuikens - pluimvee - koolhydraten - sojabonen - spijsverteringsstelsel - spijsverteringskanaal - diergezondheid - fermentatie - kinetica - darmen - morfologie - blindedarm - melkzuurbacteriën - immunoglobulinen - voedselbeperking - pluimveevoeding - diervoeding - broilers - poultry - carbohydrates - soyabeans - digestive system - digestive tract - animal health - fermentation - kinetics - intestines - morphology - caecum - lactic acid bacteria - immunoglobulins - food restriction - poultry feeding - animal nutrition
    Odour from pig production facilities: its relation to diet
    Dinh Phung, P.D. Le; Becker, P.M. ; Aarnink, A.J.A. ; Jongbloed, A.W. ; Peet-Schwering, C.M.C. van der - \ 2004
    Wageningen : Agrotechnology and Food Innovations (Rapport / Agrotechnology & Food Innovations 115) - ISBN 9789067547666 - 66
    varkensstallen - stankemissie - varkensvoeding - voersamenstelling - eiwitgehalte - koolhydraten - pig housing - odour emission - pig feeding - feed formulation - protein content - carbohydrates
    Onderzoek naar de mogelijkheden om de geur van varkens aangenamer te maken
    Housing conditions and carbohydrate source affect within-day variation of energy metabolism in growing pigs
    Rijnen, M.M.J.A. ; Borne, J.J.G.C. van den; Schrama, J.W. ; Gerrits, W.J.J. - \ 2003
    In: Progress in research on energy and protein metabolism / Souffrant, W.B., Metges, C.C., Wageningen : Wageningen Academic Publishers (EAAP Scientific Series 109) - ISBN 9789076998244 - p. 367 - 370.
    varkens - varkensstallen - energiemetabolisme - circadiaan ritme - koolhydraten - pigs - pig housing - energy metabolism - circadian rhythm - carbohydrates
    In the present study, effects of housing conditions (i.e. individual vs. group housing) and carbohydrate source (i.e. sugar beet pulp vs. maize starch) on energy metabolism and circadian rhythms in energy expenditure and physical activity were studied in growing pigs in a 2 x2 factorial design. No interactions between housing conditions and diet composition were present. Digestibility and metabolisability of dietary energy was higher for individually housed pigs than for group-housed pigs. Circadian rhythms in energy expenditure and energy expenditure for physical activity were clearly affected by housing conditions and diet composition. Total energy expenditure, as well as activity related energy expenditure, was increased during the dark phase of the day in individually housed pigs when compared with group-housed pigs. Pigs fed the sugar beet pulp based diet had a reduced energy expenditure on physical activity, which mainly occurred during the night.
    Effects of flavour absorption on foods and their packaging materials
    Willige, R.W.G. van - \ 2002
    Wageningen University. Promotor(en): A.G.J. Voragen; J.P.H. Linssen. - S.l. : S.n. - ISBN 9789058086402 - 140
    geurstoffen en smaakstoffen - absorptie - verpakkingsmaterialen - voedselverpakking - eiwitten - koolhydraten - vetten - membraanpermeabiliteit - smaakpanels - modellen - flavour compounds - absorption - packaging materials - food packaging - proteins - carbohydrates - fats - membrane permeability - taste panels - models

    Keywords: flavour absorption, scalping, packaging, food matrix, lldpe, ldpe, pp, pc, pet, pen,b-lactoglobulin, casein, pectin, cmc, lactose, saccharose, oil, modelling, storage, oxygen permeability, taste perception, sensory quality.

    Absorption of flavour compounds by linear low-density polyethylene (LLDPE) was studied in model systems representing differences in composition of the food matrix. Proteins,b-lactoglobuline and casein, were able to bind flavours, resulting in suppression of absorption of flavour compounds. Polysaccharides, pectin and carboxymethylcellulose, increased viscosity, and consequently decreased absorption. Disaccharides, lactose and saccharose, increased absorption, probably caused by a "salting out" effect of less apolar flavour compounds. The presence of a relative small amount of oil (50 g/l) decreased absorption substantially. Combined oily model systems, oil/casein and oil/pectin, showed a similar effect. The extent of absorption of flavour compounds by LLDPE was influenced by food components in the order: oil or fat >> polysaccharides and proteins > disaccharides. A model based on the effect of the polarity (log P) of flavour compounds and on their partitioning coefficients between food(matrix) and packaging material was developed. The model is able to predict absorption of flavour compounds from foods into LLDPE when lipids in the food matrix are the determining factor in flavour absorption. Results show that the model fits nicely with experimental data of real foods skim and whole milk.

    LLDPE, polypropylene (PP), polycarbonate (PC), polyethylene terephthalate (PET film and PET bottle) and polyethylene naphthalate (PEN) were immersed in a model flavour solution at different temperatures up to 14 days. The absorption rate and/or total amount of absorbed compounds increased considerably with increasing temperature. Depending on temperature, the total absorption of flavour compounds by the polyolefins (LLDPE and PP) was up to 2400 times higher than by the polyesters (PC, PET and PEN).

    The effect of absorbed flavour compounds on the oxygen permeability of low-density polyethylene (LDPE), PP, PC and PET was studied. Due to swelling of the polymers as a result of absorption of flavour compounds, LDPE and PP showed a significant increase of oxygen permeability of 21% and 130%. The oxygen permeability of PC showed a significant decrease of 11% due to occupation or blockage of the "micro-cavities" by the absorbed flavour compounds. Flavour absorption by PET did not affect the oxygen permeability significantly.

    The influence of flavour absorption LDPE, PC and PET on the taste perception of a flavour model solution and orange juice stored in glass bottles was studied with and without pieces of the respective plastic films. Although the content of flavour compounds between controls and polymer treated samples decreased substantially due to absorption, no significant effect on the taste perception of the model solution and orange juice were observed by triangular taste panel tests.

    The role of sludge retention time in the hydrolysis and acidification of lipids, carbohydrates and proteins during digestion of primary sludge in CSTR systems
    Miron, Y. ; Zeeman, G. ; Lier, J.B. van; Lettinga, G. - \ 2000
    Water Research 34 (2000)5. - ISSN 0043-1354 - p. 1705 - 1713.
    afvalwaterbehandeling - rioolslib - anaërobe behandeling - koolhydraten - lipiden - eiwitten - verzuring - hydrolyse - waste water treatment - sewage sludge - anaerobic treatment - carbohydrates - lipids - proteins - acidification - hydrolysis
    CSTR systems: completely stirred tank reactor systems
    Physiology of exopolysaccharide biosynthesis by Lactococcus lactis
    Looijesteijn, E. - \ 2000
    Agricultural University. Promotor(en): J.A.M. de Bont; J. Hugenholtz. - S.l. : S.n. - ISBN 9789058082862 - 197
    lactococcus lactis - industriële microbiologie - biosynthese - biochemie - fysiologie - oligosacchariden - koolhydraten - melkzuurbacteriën - lactococcus lactis - industrial microbiology - biosynthesis - biochemistry - physiology - oligosaccharides - carbohydrates - lactic acid bacteria

    Several lactic acid bacteria (LAB) produce exopolysaccharides (EPS). EPSs produced by LAB are a potential source of natural additives and because LAB are food grade organisms, these EPSs can also be produced in situ . The amount of EPS in milk fermented with strain NIZO B40, which produces an anionic EPS composed of glucose, rhamnose, galactose and phosphate, is very low. This relatively low concentration could be increased by optimising the culture conditions and medium composition. Using pH-controlled fermentations and a chemically defined medium, the total EPS production was highest at pH 5.8 and 25 °C. Glucose was demonstrated to be the most efficient sugar source for EPS production by L. lactis NIZO B40. With fructose as the sugar source only a minor amount of EPS was produced. The intracellular levels of sugar nucleotides, the EPS precursors, were much lower in fructose- than in glucose-grown cultures. The activity of the enzymes involved in the biosynthesis of the sugar nucleotides were however unaffected by the source of sugar but the activity of fructose-1,6-bisphosphatase (FBPase) was very low. FBPase catalyses the conversion of fructose-1,6-diphosphate into fructose-6-phosphate, an essential step for the biosynthesis of sugar nucleotides from fructose but not from glucose. Overexpression of the fbp gene resulted in increased EPS synthesis on fructose.

    Most culture conditions influenced growth as well as EPS formation and EPS synthesis itself was also influenced by the growth rate. EPS production by strain NIZO B40 starts at the exponential growth phase but continues during the stationary phase in batch cultures, indicating that EPS biosynthesis and growth are not strictly coupled. Indeed we found that non-growing cultures were still able to produce EPS, making it possible to study the influence of different culture conditions on EPS biosynthesis independent of growth.

    The amounts of EPS produced by L. lactis NIZO B40 and NIZO B891 were comparable under glucose and leucine limitation. The efficiency of EPS production, the quantity of EPS produced per quantity of glucose consumed, was however much higher under conditions of glucose limitation. The production of phosphorylated B40 EPS and of unphosphorylated B891 EPS was strongly reduced under conditions of phosphate limitation. The sugar composition of both B40 and B891 EPS and the phosphate content of B40 EPS were unaffected by the type of limitation but surprisingly, glucose limitation resulted in the production of EPSs with strongly reduced molecular masses.

    Anionic B40 EPS in suspension and a cell-associated layer of this EPS protected the bacteria against toxic copper ions and nisin, probably due to charge interactions. Furthermore, cell-associated EPS resulted in a decrease in the sensitivity of the bacteria to bacteriophages and lysozyme, most likely by masking the targets for the phages and the enzyme. The protection of EPS against nisin and bacteriophages could be a competitive advantage in mixed strain dairy starter cultures. Unfortunately, the EPS yields were not increased in the presence of copper, bacteriophages, nisin or lysozyme.

    Prebiotic effects of non-digestible oligo- and polysaccharides
    Hartemink, R. - \ 1999
    Agricultural University. Promotor(en): F.M. Rombouts; M.J.R. Nout. - S.l. : S.n. - ISBN 9789058080516 - 205
    koolhydraten - oligosacchariden - polysacchariden - darmmicro-organismen - carbohydrates - oligosaccharides - polysaccharides - intestinal microorganisms

    This thesis is the result of work carried out within a four-year multi-disciplined program, entitled ' Non-digestible oligosaccharides in foods and feed'. Within the project, four Ph.D. students were employed at the Food Chemistry, Food Microbiology, Human Nutrition and Animal Nutrition groups of the Wageningen Agricultural University. This thesis describes the studies carried out at the Food Microbiology group.

    Oligosaccharides are carbohydrates, with an average chain length of 2-10 sugar residues. Most oligosaccharides cannot be digested by the enzymes in the upper gut, nor can these compounds be absorbed. These oligosaccharides are considered non-digestible, and reach the large intestine unaltered. Non-digestible oligosaccharides (NDOs) are mainly of vegetable origin and are a normal part of the human diet. Some of the natural NDOs are now produced commercially using enzymatic methods.

    Most NDOs are completely or partially degraded and fermented by the bacterial populations in the large intestine. Some of the NDOs are considered to have a beneficial effect on the health of the host, due to the specific fermentation by two groups of intestinal bacteria, the bifidobacteria and lactobacilli. Commercial NDOs are marketed as a healthy ingredient, due to this selective fermentation, in several Western countries.

    Chapter 1 describes the gastrointestinal tract and the bacterial composition in each part thereof. The same chapter gives an overview of the current knowledge of the fermentation of NDOs by intestinal bacteria and the effects on the host health, as far as known.

    Chapters 2 and 3 describe the effect of the two types of NDOs, currently available on the Dutch market, on the etiology of dental caries. When consumed, residues of NDOs in foods may remain in the oral cavity. In the oral cavity many different bacteria are capable of degrading and fermenting carbohydrates, which results in the formation of acid and, possibly, dental lesions and caries. NDOs, being carbohydrates, may thus be fermented and are, in theory, a risk factor for dental caries.

    In Chapter 2 the degradation and fermentation of fructooligosaccharides (FOS) by the oral microflora is described. It can be concluded that this class of NDOs can be fermented by the most common bacterial species. These NDOs can be considered cariogenic, in vitro , but in vivo studies have to be carried out to determine the actual risk for dental caries.

    In Chapter 3, the degradation and fermentation of transgalactosyl-oligosaccharides (TOS) by the oral microflora is described. It was concluded that this class of NDOs is not, or very slowly, degraded and fermented. These NDOs are not considered a risk factor for dental caries.

    Within the framework of the project, the Food Chemistry group synthesized and purified a large number of oligosaccharide mixtures from plant cell walls. As these purifications are laborious and the total quantities of pure oligosaccharides are very small, it was decided to determine the fermentation of plant cell wall compounds by intestinal bacteria. These plant cell wall compounds are available in large quantities and thus could be used for screening studies.

    Chapter 4 describes the degradation and fermentation of such a plant cell wall polysaccharide, xyloglucan. Xyloglucan is present in many edible plants, but it is commercially prepared from tamarind seeds. The more (chemically) complex the compound the more enzymes are necessary for degradation, and the less bacteria are capable of fermenting the compound. Xyloglucan has a relatively simple chemical structure, but, surprisingly, only very few intestinal bacteria were capable of degrading this compound. The second remarkable conclusion was that most of the bacteria capable of degrading xyloglucan, belonged to the genus Clostridium . Previously, this genus has not been considered of major importance for polysaccharide degradation in the intestine.

    Chapter 5 describes the degradation of a second plant cell wall polysaccharide, guar gum, a galactomannan. Like xyloglucan, galactomannans are part of the cell wall of many plants. Guar is commercially produced from the seeds of the Cyamopsis tetragonoloba tree and used as a thickening agent in many foods. Guar also has a relatively simple structure. Nevertheless, only three different bacterial species, capable of degrading guar, could be isolated from human and animal faeces. One of these, Bifidobacterium dentium was considered to be mainly an oral species, but, using guar, could also be isolated from faeces. The same species could also be isolated from samples of saliva from 19 out of 20 volunteers. A second species, Streptococcus bovis could only be isolated from animal faeces, whereas the third species, Clostridium butyricum was present in human and animal faeces. The latter species produced large amounts of gas, and can thus be considered responsible for the increased flatulence observed after the ingestion of guar.

    Chapter 6 describes the differences in the fermentation of different oligosaccharides by human faecal inocula. In addition three polysaccharides were used in these studies. All donors had received the same diet and four samples were taken from each volunteer. The results show large differences between test compounds within the same volunteer, and large differences between volunteers on the same test compound. It can be concluded that the fermentation is largely dependent on host (genetic) factors, and not on dietary factors. It was also concluded that formation of gas is correlated with the formation of butyric acid. Butyric acid is considered to be important for the health of the intestinal wall. Gas production can thus be used as a simple screening method for butyrate production.

    Within the project the variations in the bacterial composition of human and pig faeces have been studied. It was concluded in the early stages of the project that no methods existed for the reliable quantification of two major intestinal bacterial groups, bifidobacteria and lactobacilli. Two new methods had to be developed for the quantification of these bacterial groups.

    Chapter 7 describes the development of a new medium for bifidobacteria, the RB medium. Selectivity is based on raffinose, propionate and lithiumchloride. The medium is not yet an ideal medium for the isolation and quantification for bifidobacteria but, compared with media currently used, it is more selective.

    Chapter 8 describes the development of a new medium for lactobacilli, the LAMVAB medium. Selectivity is based on vancomycin and a low pH (5.0). The combination of vancomycin and low pH inhibits practically all other intestinal bacteria. LAMVAB has successfully been employed to isolate lactobacilli from faeces from a large number of animals.

    The two newly developed media were compared with two other media, that are used regularly. The results of this comparison is described in Chapter 9 . The media were used to isolate bifidobacteria and lactobacilli in human and cat faeces and pig small intestinal contents. The three media for bifidobacteria performed equally well for human faeces, but for the other two kinds of samples, the RB medium performed better. For lactobacilli, LAMVAB performed better for all three types of samples tested.

    Chapter 10 discusses the results of this thesis and some recommendations for further research are given.

    As conclusion it can be stated that very few NDOs are degraded and fermented selectively by bifidobacteria. This was confirmed in Chapters 2 and 6, in which degradation and fermentation of FOS by other bacterial groups is described.

    Although FOS and TOS are found to be possibly cariogenic, it is not likely that either oligosaccharide will cause caries under normal conditions.

    Xyloglucan and guar are degraded only by a limited number of bacteria. Unexpectedly, clostridia played a major role in the degradation of both substrates. Both substrates may be a good substrate for the production of new NDOs, but considering the results it is unlikely that these oligosaccharides are a good substrate for lactobacilli or bifidobacteria.

    RB and LAMVAB are new media, which are suitable for the quantitative isolation of bifidobacteria and lactobacilli from human faeces. LAMVAB is also suitable for animal faeces. Both media are more selective than the media used at present.

    Verwijdering oligosachariden uit reactor verhoogt opbrengst.
    Boon, M.A. ; Janssen, A.E.M. - \ 1998
    Voedingsmiddelentechnologie 25 (1998). - ISSN 0042-7934 - p. 11 - 13.
    oligosacchariden - koolhydraten - opbrengsten - enzymprecursors - kinematica - lactose - disacchariden - oligosaccharides - carbohydrates - yields - enzyme precursors - kinematics - disaccharides
    De enzymatische productie en toepassing van oligosachariden uit lactose. Resultaten van modelberekeningen zijn belicht
    Seed development and carbohydrates
    Wittich, P.E. - \ 1998
    Agricultural University. Promotor(en): M.T.M. Willemse; A.A.M. van Lammeren; C.J. Keijzer. - Wageningen : Wittich - ISBN 9789054858553 - 178
    zaadzetting - zaden - formatie - plantenfysiologie - plantenontwikkeling - vruchten - rijp worden - planten - embryologie - metabolisme - plantenvoeding - assimilatie - koolhydraten - vicia faba - gasteria verrucosa - organische scheikunde - seed set - seeds - formation - plant physiology - plant development - fruits - ripening - plants - embryology - metabolism - plant nutrition - assimilation - carbohydrates - vicia faba - gasteria verrucosa - organic chemistry

    Seeds assure the plant the onset of a next generation and a way of dispersal. They consist of endosperm and an embryo (originating from gametophytic tissue), enveloped by a seed coat (sporophytic tissue). Plants generate different types of seeds. For instance, the endosperm may either be consumed by the embryo during seed development or retained for use by the embryo during germination. Differences in timing of endosperm digestion can be illustrated with broad bean ( Vicia faba ) and Gasteria verrucosa . Broad bean forms seeds in which the endosperm has been consumed by the fully developed embryo, while the embryo of Gasteria is less developed and surrounded by a large amount of endosperm for use during germination.

    An important factor in seed development is the distribution, storage, and utilization of carbohydrates, since carbohydrates are a major source of energy for cell growth. In this thesis the carbohydrate distribution is studied in developing ovules and seeds of maize ( Zea mays ) and Gasteria , by identifying the cells and tissues in which sucrose is degraded. Sucrose is the main carbohydrate supplied by these plants in the developing seeds. The sucrose degrading activity of the enzymes sucrose synthase and invertase indicates the destination of the sucrose transport (Chapters 9 and 10). Immunocytochemical and histochemical techniques are used for the localization of these enzymes in situ .

    The results obtained in this study on maize (Chapter 2 and 3) and Gasteria seed development (Chapters 4 and 5) show a general pattern of carbohydrate transport. First, the greatest amount of carbohydrates is applied for the development of the seed coat and nucellus (sporophytic tissues). An example of such a carbohydrate consuming process is the deposition of phytomelan in the seed coat of Gasteria . Phytomelan is a black cell wall component and chemically very inert. Histochemical and electron microscopy observations (Chapters 6 and 7) show that callose forms a mould for the deposition of phytomelan. The breakdown products of callose (glucose monomers and polymers) seem to be used for the synthesis of the phytomelan. Chemical analysis reveals that phytomelan is a complex polyphenolic polymer, and not a melanin (Chapter 8). Second, carbohydrate transport to the sporophytic tissues is followed by transport of most carbohydrates into the endosperm. These carbohydrates will be used for endosperm growth and for storage. Finally the main carbohydrate flow will go to the embryo. The pattern of carbohydrate usage observed in maize and Gasteria was used to generate a general model for angiosperm seed development (Chapter 10). The model explains differences between seeds by relating carbohydrate distribution during seed development to the timing of seed dispersal.

    Qualitätsbestimmung bei Lagerkartoffeln
    Hak, P.S. ; Oosterhaven, J. - \ 1997
    Der Kartoffelbau 48 (1997)11. - ISSN 0022-9156 - p. 418 - 420.
    opslag - chemische samenstelling - planten - chemische analyse - koolhydraten - aldehyden - ketonen - zetmeel - cellulose - kwaliteit - prestatieniveau - fabrieksaardappelen - storage - chemical composition - plants - chemical analysis - carbohydrates - aldehydes - ketones - starch - quality - performance - starch potatoes
    Onderzoek naar oorzaken van veroudering bij het bewaren van fabrieksaardappelen. De balans tussen het zetmeel- en suikergehalte is een indicator voor de kwaliteit van frieten
    Wheat bran glucuronoarabinoxylans : biochemical and physical aspects
    Schooneveld - Bergmans, M.E.F. - \ 1997
    Agricultural University. Promotor(en): A.G.J. Voragen; G. Beldman. - S.l. : Schooneveld-Bergmans - ISBN 9789054857167 - 125
    graansoorten - maling - Triticum aestivum - tarwe - hexaploïdie - voedsel - voedingsmiddelen - koolhydraten - zetmeel - vezel - polysacchariden - structuur - chemische reacties - cereals - milling - Triticum aestivum - wheat - hexaploidy - food - foods - carbohydrates - starch - fibre - polysaccharides - structure - chemical reactions

    Arabinoxylans are present in cereal cell walls and in vitro they have interesting physicochemical properties, such as viscosity and gelation. Although many studies on these properties were reported for wheat flour arabinoxylan, not much research has been directed towards exploitation of these polysaccharides as food gum. For that purpose glucuronoarabinoxylans of wheat bran, a cheap by-product of the cereal industry, were studied with regard to their extractability, their structural and physicochemical properties.

    Approximately 50% of the glucuronoarabinoxylans of wheat bran cell wall material were recovered in high purity by barium hydroxide extraction at 70 to 95°C. Delignification or other treatments to open up the cell wall structure were not effective in increasing the yield. The extracted glucuronoarabinoxylans were very diverse in chemical structure and physicochemical properties. About 30% of them had a low degree of substitution, were easily degradable by xylanolytic enzymes and hardly influenced the viscosity of the solvent as a result of extensive aggregation. Over 50% of them had a high degree of substitution, were supposed to contain dimeric branches of arabinose and xylose, were scarcely degradable by xylanolytic enzymes, gave moderate viscosity to solutions and were very effective in stabilizing emulsions. The structure of these glucuronoarabinoxylans could only be speculated upon and it could not be enzymatically modified as a consequence of its complexity and the lack of appropriate enzymes. The remaining glucuronoarabinoxylans either had an intermediate or very high degree of substitution, of which the latter was presumed to be connected to lignin-fragments.

    Gel-forming glucuronoarabinoxylans were recovered only in low yield by dilute alkali extraction and subsequent purification was necessary. These feruloylated glucuronoarabinoxylans gelled upon addition of oxidative agents, of which peroxide - peroxidase, glucose - glucoseoxidase - peroxidase and ammonium persulphate were investigated. In comparison with wheat flour arabinoxylans, those of wheat bran appeared to give less flexible networks at high concentration, which was ascribed to their high degree of substitution and high ferulic acid content. Of the dimers formed upon cross-linking, the generally known diferulic acid, being a 5-5 coupled dimer, was only present in relatively low amounts. Dimers, in which the 8-position of the ferulic acid residue is involved were preponderant. The distribution of the dimers was not affected by the type of cross- linking agent or the type of arabinoxylan. However, the presence of lignin fragments in the bran extract was presumed to cause a low ferulic acid recovery upon cross-linking.

    Physiological effects of consumption of resistant starch
    Heijnen, M.L. - \ 1997
    Agricultural University. Promotor(en): A.C. Beynen; P. Deurenberg; J.M.M. van Amelsvoort. - S.l. : Heijnen - ISBN 9789054856511 - 163
    voeding - zetmeel - voedingsmiddelen - voedsel - koolhydraten - vezel - nutrition - starch - foods - food - carbohydrates - fibre

    Resistant starch (RS) is defined as the sum of starch and products of starch degradation not absorbed in the small intestine of healthy individuals. Thus, RS enters the colon where it may be fermented. In this respect, RS resembles some types of dietary fibre. Three types of RS are being discerned: RS 1 , physically entrapped starch; RS 2 , uncooked starch granules; RS 3 , retrograded starch. The estimated current mean per capita RS intake in the Netherlands is 5 g/d. The amount of RS in foods can be manipulated by the choice of raw products and food processing techniques. This is of potential interest if an increased RS consumption would be beneficial for human health. In this thesis several of the hypotheses concerning putative positive effects of RS consumption on human physiology are studied. Daily consumption of up to 32 g RS 2 or RS 3 was tolerated well by healthy individuals and increased colonic fermentative activity and stool weight. Replacement of 27 g digestible starch by RS 2 reduced diet-induced thermogenesis and postprandial glucose and insulin responses proportionally to the amount of indigestible carbohydrate consumed. When compared with an equivalent amount of glucose, daily supplementation of 30 g RS 2 or RS 3 for 3 wk did not affect serum lipid concentrations in healthy subjects, and daily supplementation with 32 g RS 2 or RS 3 for 1 wk did not affect putative risk factors for colon cancer, subjective feelings of hunger, faecal ammonia excretion and apparent absorption of magnesium, calcium and phosphorus in healthy individuals. No differences were observed between RS 2 and RS 3 , in the parameters studied. In piglets, dietary RS 3 , but not RS 2 , shifted nitrogen excretion from urine to faeces, and RS 2 reduced apparent magnesium and calcium absorption. In rats, dietary RS 2 , but not RS 3 , increased apparent, but not true magnesium absorption. It was concluded that daily consumption of up to 32 g RS 2 or RS 3 , is not unfavourable for healthy individuals, but it also does not have great beneficial effects on human physiology, at least for the parameters and time span studied in this thesis. Especially the significance for human health of increased activity and site of fermentation in the colon, and the possible role of the various types of RS in the prevention of colon cancer should be studied further.

    Influence of the enchytraeid worm Buchholzia appendiculata on aggregate formation and organic matter decomposition.
    Marinissen, J.C.Y. ; Didden, W.A.M. - \ 1997
    Soil Biology and Biochemistry 29 (1997)3-4. - ISSN 0038-0717 - p. 387 - 390.
    organische verbindingen - bodem - bodemchemie - aardwormen - cellulose - koolhydraten - decompositie - organic compounds - soil - soil chemistry - earthworms - cellulose - carbohydrates - decomposition
    Enchytraeid worms were kept in <0.3 mm sieved sandy loam subsoil mixed with ground wheat, for 6 weeks at 16°C. Sieved soil with organic matter but without worms was also incubated. The soil was then allowed to air-dry slowly during 6 weeks. Enchytraeid casts were collected from the surface of the soil with worms, and the remaining soil was separated into three size fractions by dry sieving. All size fractions were analysed for stability and %C, and mineralisation potential. The amount of soil in the fraction > 0.3 mm (including the casts) was larger in the presence of enchytraeid worms, at the cost of soil from the fraction 0.3 0.03 mm. The %C in both soils was highest in the fraction < 0.03 mm. Activity of enchytraeids significantly decreased the %C in the fraction > 0.3 mm. Fresh excrements, representing 0.5% of the soil, were very high in organic matter content. Mineralisation (expressed as percentage of C that was mineralised) was highest in the fraction <0.03 and lowest in the 0.3-0.03 fraction. Excrements showed very high mineralisation rates. Enchytraeid activity enhanced mineralisation in the fraction > 0.3 ram. Aggregates > 0.3 mm from the treatment with worms dispersed less clay after shaking with water than those from the treatment without worms. Although the influence of enchytraeid worms on total C-content and mineralisation was small, the changes in C of the different size fractions showed that enchytraeids influenced the active fraction of the C in the soil considerably by consuming litter, thereby locating it inside soil aggregates and linking the organic matter to clay particles.
    Isolation and characterisation of starch biosynthesis genes from cassava (Manihot esculenta Crantz)
    Munyikwa, T.R.I. - \ 1997
    Agricultural University. Promotor(en): E. Jacobsen; R.G.F. Visser. - S.l. : Munyikwa - ISBN 9789054858416 - 128
    koolhydraten - polysacchariden - biosynthese - genen - genomen - manihot esculenta - cassave - carbohydrates - polysaccharides - biosynthesis - genes - genomes - manihot esculenta - cassava

    Cassava (Manihot esculenta Crantz) is a tropical crop grown for its starchy thickened roots, mainly by peasant farmers, in the tropics, for whom it is a staple food. There is an increasing demand for the use of cassava in processed food and feed products, and in the paper and textile industries amongst others. This thesis describes research on the cloning of the genes encoding ADP-glucose pyrophosphorylase small and large subunits (AGPase B and S, respectively) and granule bound starch synthase II (GBSSII). These genes and their products were extensively characterised to determine their role in starch biosynthesis in cassava. Functional verification of the genes was carried out by transforming potato and cassava followed by analysis of the starch produced by the transgenic plants.

    In Chapter 1 cassava production in the world in general and in Zimbabwe in particular is examined against the backdrop of new cloning and transformation strategies to improve starch quality and quantity. The development of cassava cultivars whose starches have novel physico-chemical properties by genetic modification of the process of starch biosynthesis is examined therein. The main criteria for these new cultivars to emerge are set forth as being: the availability of cloned and characterised starch biosynthesis genes, a universally applicable transformation and regeneration procedure for cassava, transfer to appropriate cassava cultivars, and biosafety analysis of transgenic cassava plants before disbursement to farmers.

    The cloning of the cassava starch biosynthesis genes encoding granule bound starch synthase II (GBSSII) and the large and small subunits of ADP-glucose pyrophosphorylase (AGPase) is described in Chapters 2 and 3. The cloning of GBSSII reveals that there is indeed a second isoform of this enzyme in cassava as in other plants species. While sharing very little amino acid sequence homology with cassava GBSSI the GBSSII isophorm shares high amino acid sequence homology to other GBSSII genes from pea and potato. Cassava GBSSII seems to be more important in leaf tissue where it is more highly expressed than in tuber tissue where GBSSI predominates. Mapping of GBSSII revealed that this is a single copy gene located on the male derived linkage group T of the cassava mapping population.

    Cloning of the cassava genes coding for the small (B) and large subunit (S) of AGPase revealed interesting aspects about the cassava enzyme. The cassava AGPase is likely to be heterotetrameric in constitution as had been found in other plant species. Comparison of the cassava AGPase sequences with those of already cloned AGPases revealed that AGPase B is more similar to small subunit genes from other plants than to cassava AGPase S coding for the large subunit (Chapter 3). Segregation analysis of a cassava mapping population revealed that AGPase S is a single copy gene that is localised on the female derived linkage group E of the cassava genetic map. Both genes are expressed in all cassava tissues but AGPase B was shown to have a higher steady state mRNA level than AGPase S especially in leaf and tuber tissue. Post-transcriptional control of small subunit polypeptide levels could be inferred from the discrepancy between AGPase B mRNA and polypeptide levels. The AGPase enzyme activity was much higher in young cassava leaves than older leaves and tubers. Cassava leaf AGPase activity was increased 3 fold by the addition of 3-PGA (3-phospho-glycerate) and inhibited by up to 90% in the presence of inorganic phosphate (Pi). The tuber enzyme was relatively unaffected by 3PGA, but was highly inhibited by Pi.

    In order to verify the biological role of the AGPase B gene antisense constructs were made of the cassava AGPase B behind a CaMV35S promoter (chapter 3). This was transferred into potato plants by Agrobacterium tumefaciens. While the 224 transgenic antisense AGPase B potato plants did not differ in appearance from normal potato plants, 45 transgenic plants, however, had more numerous and smaller tubers than control plants. Antisense plants with reduced AGPase B mRNA levels had 1.5 to 3 times less starch than tubers from the control plants. The levels of the soluble sugars in the antisense plants increased significantly (up to 10 times more glucose, 6 times the amount of fructose, and 5 times the amount of sucrose) when compared to those found in control plants. These results show that a heterologous gene from cassava can have an antisense effect in potato, but that the number of plants required to find plants exhibiting maximum antisense effect has to be very large. This is probably due to sequence homology differences between the cassava AGPase B and potato AGPase B genes which share only 68% amino acid sequence homology.

    Chapter 5 describes the further development of an efficient, time and labour saving protocol for transforming cassava based on stringent selection of the luciferase (firefly) marker gene. In addition the first reported transformation of cassava with a gene (AGPase B) other than a marker gene is described. An antisense construct was made for transforming cassava. This consisted of the cassava AGPase B gene which was placed in antisense orientation behind the CaMV35S promoter. This was then coupled to the luciferase gene driven by another CaMV35S promoter. After particle bombardment of cassava FEC transgenic tissue was selected using three different selection regimes: non stringent luciferase selection, stringent luciferase selection and combined chemical (phosphinothrycin) and luciferase selection. Stringent luciferase selection whereby luciferase positive FEC units were precisely pinpointed, isolated and cultured was found to be the most effective and time saving method. It was possible to generate cultures having more than 90% luciferase positive FEC tissue after 12 weeks of stringent LUC selection, compared to 45% and <1 % for combined selection and non stringent selection respectively. The number of luciferase positive mature embryos generated was directly proportional to the percentage of luciferase positive tissue in the original FEC culture. Stringent luciferase selection enabled the time taken for production of transgenic cassava plants to be reduced to 28-36 weeks as compared to 8 months to a year with no stringent selection or LUC/PPT selection.

    Cassava plants carrying the AGPase B antisense gene had extremely low levels of starch, compared to control plants, as shown by iodine staining of in vitro induced thick stems. In plants exhibiting the highest AGPase B antisense effect, starch formation was limited only to the epidermal layer. These results functionally confirm the identity of cassava AGPase B as well as emphasising the critical role of AGPase in starch formation in cassava.

    A discussion about the significance and implications of cloning cassava genes and producing transgenic cassava for culture in developing countries is carried out in Chapter 6. While there are clearly many economic and nutritional benefits to producing transgenic cassava, for resource poor farmers, many people in the South are not aware of the biosafety implications of growing transgenic crops. It is further emphasised that discussions and debate should be initiated to make local communities aware of the issues surrounding transgenic crops and their products. In addition it is recommended that some form of international legal framework be set up to ensure that resource poor farmers are not disadvantaged by the patenting of material originating from their communities by individuals and companies in the North. This thesis clearly demonstrates how it will be possible in the near future to produce new cassava cultivars carrying the appropriate genes to affect pronounced changes on tuber productivity and starch quality.

    Samenstelling koolhydraatfractie in partijen aardappelstoomschillen, ontsloten aardappelzetmeel, tarwe-indampconcentraat en tarwezetmeel
    Smits, B. ; Gelder, A.H. van; Cone, J.W. - \ 1996
    Lelystad : ID-DLO (Rapport / ID-DLO no. 96.013) - 34
    diervoeding - voer - diervoedering - varkens - koolhydraten - zetmeel - animal nutrition - feeds - animal feeding - pigs - carbohydrates - starch
    Preservation of plant residues in soils differing in unfilled protective capacity
    Hassink, J. ; Whitmore, A.P. - \ 1996
    Soil Science Society of America Journal 60 (1996)2. - ISSN 0361-5995 - p. 487 - 491.
    koolhydraten - cellulose - decompositie - organische verbindingen - bodem - bodemchemie - carbohydrates - cellulose - decomposition - organic compounds - soil - soil chemistry
    Enzymic modification of cellulose - xyloglucan networks : implications for fruit juice processing = Enzymatische modificatie van cellulose - xyloglucaan netwerken
    Vincken, J.P. - \ 1996
    Agricultural University. Promotor(en): A.G.J. Voragen; G. Beldman. - S.l. : Vincken - ISBN 9789054855101 - 159
    appels - malus - koolhydraten - aldehyden - ketonen - zetmeel - cellulose - apples - malus - carbohydrates - aldehydes - ketones - starch - cellulose

    Xyloglucans play an important role in connecting cellulose microfibrils in the primary coli wall of plants, and the resulting cellulose-xyloglucan network is thought to determine the strength of these walls. Xyloglucans were isolated from apple fruit and potato tuber cell wall material by alkaline extraction and their primary structures were determined. Major differences between these two polysaccharides were their degree of backbone branching and the presence of fucosyl and arabinosyl residues.

    The substrate specificity of three ondoglucanases from Trichoderma viride (endol, endolV and endoV) was investigated. The target substrate of endol is cellulose, that of endolV xyloglucan, whereas endoV is the most versatile endoglucanase having the ability of degrading both substrates. EndolV and endoV differ in their mode of action towards potato xyloglucan. Further, strong indications were obtained that xyloglucanase activity is related to a long array of substrate-binding sites.

    The degradation of the cellulose-xyloglucan network in isolated coli wall material from apple fruit involves several glucanase activities. Xyloglucanase activity is important to make cell wall embedded cellulose more accessible to true cellulolytic enzymes such as endol and cellobiohydrolase. Extensive degradation is required because xyloglucan fragments having a backbone of 20 glucosyl residues (five building units) still bind to cellulose surfaces. These results might explain why fungi excrete so many different kinds of endoglucanases.

    When the cell walls of living apple fruit tissue were treated with pectin lyase and a mixture of glucanases from Trichoderma viride (liquefaction), the ease with which the apple tissue disintegrated, seemed to depend on the maturity of the fruit. The disintegration of apple fruit tissue during liquefaction correlates to the level of (ripeningrelated) xyloglucan endotransglycosylase activity in apple fruit. An hypothesis for the synergism of fungal and plant glucanases is put forward. Under certain circumstances (controlled liquefaction) the cellulose-xyloglucan network can be modified in such a way, that a stable cellulose-based cloud is formed in the resulting apple juice. The significance of these observations for juice manufacturing is discussed.

    NVVL-Workshop: Vezel, het belang voor de gezonde mens.
    Olthof, M. - \ 1996
    Voeding 57 (1996)12. - ISSN 0042-7926 - p. 21 - 23.
    koolhydraten - cellulose - spijsvertering - effecten - vezel - voedsel - voedingsmiddelen - gezondheid - darmen - voeding - zetmeel - voedingsvezels - welzijn - carbohydrates - digestion - effects - fibre - food - foods - health - intestines - nutrition - starch - dietary fibres - well-being
    Verslag van een workshop, georganiseerd door de werkgroep Voeding van de NVVL. Ingegaan is op de aspecten: fermentatie in de dikke darm; invloed op bloedlipidenconcentraties; invloed op de absorptie van mineralen
    Interaction between carbohydrates and fat in pigs : impact on energy evaluation of feeds
    Bakker, G.C.M. - \ 1996
    Agricultural University. Promotor(en): M.W.A. Verstegen; A.W. Jongbloed. - S.l. : Bakker - 193
    voer - voedingswaarde - koolhydraten - vetten - varkens - feeds - nutritive value - carbohydrates - fats - pigs

    In marketing pigs, nearly 50% of the costs are those of the feed. Therefore, it is necessary to know the nutritional value as accurately as possible.

    In the Netherlands, pigs receive in general (99%) compound feeds, containing all the nutrients they require. Cereals used to be the major ingredients. However, their proportion was reduced from 40% in 1970 to 15% in the eighties. The use of ingredients other than cereals or tapioca in compound feeds affected the chemical composition of the pig diet: from feeds with a large amount of starch towards feeds containing less starch but more fibrous polysaccharides, that are often called non-starch polysaccharides (NSP). Starch and NSP differ in many aspects: in chemical structure; in the type of nutrients they supply and their effect on other nutrients in the digestion process; efficiency of utilization for energy gain; and other, non-nutritional, aspects.

    In order to have maximum benefit of their potential nutrient supply, most nutrients need to be digested and absorbed before reaching the terminal ileum. These nutrients are: amino acids from protein, fatty acids from lipids, and glucose from starch and sugars. If they disappear from the large intestine, the energy value of the nutrients will be lower, resulting in a reduced feeding value of the total feed. On the other hand, NSP are fermented mainly in the hindgut, supplying energy to the pig in the form of volatile fatty acids.

    In general, the energy of pig feeds is evaluated by considering the differential contribution of digestible nutrients to energy supply. Energy evaluation is based on three assumptions: (1) that both the chemical composition and the digestibility coefficients of ingredients in a feed are known and can be derived from feedstuff tables; (2) that the amounts of digestible nutrients in the different ingredients are additive and that there are no interactions between ingredients; and (3) that after digestion the contribution of each nutrient to energy supply is independent of the amounts of other nutrients. Because NSP have a relatively low energy density, they are often supplemented with fat to maintain a certain energy density in the diet. Hence it is assumed that the feeding values are additive. It was found, however, that the combination of NSP rich by-products and fat resulted in less energy gain in pigs than an iso-energetic combination of cereals and fat or by-products separately. It was concluded that the NSP and fat interacted on energy supply to the pigs.

    It is important to know whether the interactive effect between fat and fermentable carbohydrates takes place prior to the terminal ileum or in the hindgut of the pig. To be able to measure this, a new technique of ileo-cecal cannulation was developed: the steered ileo-cecal valve (SICV). In contrast to other techniques, in this technique the gut remains intact. After testing it with high fibrous diets, it was concluded that both ileal and total tract digestibility can be measured in the same pig. For this, the use of a marker is recommended.

    To investigate the interaction between NSP and fat, an experiment was performed with 12 diets, in a 4 x 3 factorial arrangement with four amounts of animal fat and three sources of carbohydrate. The amounts of animal fat added to the diets were : 0 (o), 35 (1), 70 (m) and 105 (h) g per kg. The three sources of carbohydrate were maize starch (M), purified cellulose (C) and toasted soya bean hulls (S). The cellulose was. used as a source of poorly fermentable carbohydrate and the soya bean hulls as a source of easily fermentable carbohydrate. These diets were given to pen-housed pigs from 30 to 105 kg live weight, which period is the growing-finishing period in practice. In these pigs both digestibility of the diets and the energy gain were measured. In a separate set of pigs, the digestibility of nutrients at the terminal ileum was measured.

    All the measured digestibility coefficients were lower than expected from the feedstuff table. This effect was partly attributed to differences in techniques for estimating digestibility between the present experiment (practical conditions) and the experiments supplying data for the feedstuff table. Most of the tabulated values are obtained under well-controlled laboratory conditions. It was found that housing pigs in groups in pens, as in common practice, reduced the digestibility of organic matter with 1.5 %-units, compared to pigs housed in metabolism crates. For protein this difference was larger: on average 3.7 %-units. Feeding high fibrous diets tended to increase these differences.

    In addition, the assumption of additivity of digestible nutrients in ingredients within a diet was not correct, especially when high fibrous ingredients were used. When cellulose or soya bean hulls were included in the diet, digestibility of protein and fat was worse. It was concluded that intake of dry matter or fibrous material increased endogenous secreted protein with 36.5 g/d per kg NSP consumed, which reduced apparent digestibility. In addition, microbial protein synthesis of 116.6 g/d per kg fermented NSP also reduced apparent protein digestibility. Moreover, the added fat was less digestible at the terminal ileum when combined with cellulose or soya bean hulls in a diet, than when they were all fed separately. The total tract digestibility of the added fat was 91 % with the low fibre diet, but 83% when combined with cellulose and 87% when combined with soya bean hulls.

    The energy gain predicted from the measured digestible nutrients was compared with the net energy gain as actually achieved. It was concluded that the utilization of energy from fermentable carbohydrates was relatively low: 0.43. This was partly ascribed to energy losses in methane and energy losses in volatile fatty acids in faeces. Of the digestible energy from fermentable carbohydrates 0.81 to 0.90 was available for energy gain in the form of volatile fatty acids. In addition, increased weight of the empty gastrointestinal tract was found, which may have required a large part of the available energy for maintenance, leaving less energy for growth.

    It is concluded, that digestibility of nutrients should be measured both at the terminal ileum as over the total tract, when large amounts of fermentable carbohydrates are included in the diet. They should be measured under practical conditions. The variation in energy gain between pigs, however, remains relatively large.

    Goed verteerbaar en smakelijk rantsoen noodzakelijk voor roze-vleeskalveren
    Schans, F.C. van der - \ 1995
    Praktijkonderzoek / Praktijkonderzoek Rundvee, Schapen en Paarden (PR), Waiboerhoeve 8 (1995)5. - ISSN 0921-8874 - p. 25 - 26.
    kalveren - koolhydraten - karkassamenstelling - samenstelling - ontwikkeling - voer - groei - voedingswaarde - smakelijkheid - calves - carbohydrates - carcass composition - composition - development - feeds - growth - nutritive value - palatability
    Aan roze-vleeskalveren zijn krachtvoeders met variërende gehaltes aan verschillende koolhydraten gevoerd. Deze verschillende gehaltes aan zetmeel, suiker en ruwe celstof hadden geen effect op de voeropname, groei of slachtkwaliteit van de kalveren.
    A molecular analysis of L-arabinan degradation in Aspergillus niger and Aspergillus nidulans
    Flipphi, M.J.A. - \ 1995
    Agricultural University. Promotor(en): A.J.J. van Ooyen; J. Visser. - S.l. : Flipphi - ISBN 9789054853923 - 165
    aspergillus - celwanden - koolhydraten - cellulose - celmembranen - fermentatie - voedselbiotechnologie - glycosidasen - polysacchariden - genexpressie - pleiotropie - moleculaire genetica - aspergillus - cell walls - carbohydrates - cellulose - cell membranes - fermentation - food biotechnology - glycosidases - polysaccharides - gene expression - pleiotropy - molecular genetics

    This thesis describes a molecular study of the genetics ofL-arabinan degradation in Aspergillus niger and Aspergillus nidulans. These saprophytic hyphal fungi produce an extracellular hydrolytic enzyme system to depolymerize the plant cell wall polysaccharideL-arabinan. Chapter 1 surveys the occurrence, properties and applications ofL-arabinanolytic enzymes (arabinases). The A.niger system, which constitutes an endolytic endo-1,5-α-L-arabinase (ABN A) and two distinct α-L-arabinofuranosidases (ABF A and ABF B), has been a frequent subject of investigation in the past and represents the best characterizedL-arabinanolytic system to date. These three enzymes are all glycosylated. Current knowledge on the induction of fungal arabinase expression is summarized in this Chapter. Furthermore, the structure of the polysaccharide substrate and its function in the plant cell wall matrix are introduced.

    In Chapters 2 to 5, the cloning and characterization of the structural genes coding for the three glycosyl hydrolases from the A. nigerL-arabinan-degrading complex are described. A. niger abf A and abf B ar e the first eukaryotic ABF-encoding genes to be isolated and sequenced, abn A is the first ABN-encoding gene published. Chapter 2 reports on the isolation of the abf A gene encoding ABF A, the minor extracellular ABF. This gene could be cloned by utilizing ABF Aspecific cDNA as the probe. This cDNA was immunochemically identified from a cDNA library generated fromL-arabitol-induced myceliurn of an A. nigerD-xylulose kinase mutant. This mutant is unable to grow onL-arabitol and features enhanced expression of all three arabinases when transferred to medium containing this pentitol as sole carbon source. In Chapter 3 , the cloning of the ABN A-encoding gene (abn A) is described. This gene was isolated following the same strategy as with abf A, although a second cDNA library had to be generated first. The induction process was immunochemically monitored in order to establish the proper induction conditions for the new library. The abn A gene and the gene product were characterized by DNA sequence analyses of the cloned genomic DNA and the cDN A. The N-terminal amino acid sequences of ABN A and a CNBr-derived peptide were determined. Several transcription initiation sites and one polyadenylation site could be identified. The structural region codes for a protein of 321 amino acids and is interrupted by three introns. Extracellular ABN A consists of 302 amino acid residues with a deduced molecular weight of 32.5 kDa and a theoretical pl of 3.5. For the protein, an apparent pl of 3.0 and an apparent molecular weight of 43 kDa, determined upon SDS-PAGE, were previously reported. Chapter 4 documents the isolation and characterization of the abf B gene, coding for the major extracellular ABF. The determination of N-terminal amino acid sequences from ABF B and CNBr-generated peptides allowed the design of deoxyoligonucleotide mixtures which enabled the cloning of abf B. When utilized as primers in a polymerase chain reaction (PCR), ABF B-specific amplification products emerged, one of which was used to probe the gene. The abf B gene and the gene product were characterized by DNA sequence analyses of the cloned genomic DNA and of ABF B- specific cDNA isolated from the library described in Chapter 3. Several transcription initiation sites and one polyadenylation site could be identified. The structural region is a single open reading frame and codes for a protein of 499 amino acids. The mature enzyme consists of 481 amino acid residues with a deduced molecular weight of 50.7 kDa and a theoretical pl of 3.8. An apparent pl of 3.5 and an apparent molecular weight of 67 kDa, determined upon SDS-PAGE, were previously reported. The abf B gene product was suggested to be identical to the ABF purified and characterized by Kaji and Tagawa (Biochim Biophys Acta 207 : 456-464 (1970)). Considering the non-amino acid content of the latter protein, a molecular weight of 64 kDa could be deduced for ABF B. In Chapter 5 , the abf A gene and its gene product were characterized by DNA sequence analyses of the genomic DNA and of the cDNA for which the isolation was described in Chapter 2. The N-terminal amino acid sequences of ABF A and a CNBr-derived peptide were determined. One transcription initiation site and two polyadenylation sites could be identified. The structural region is interrupted by seven introns and codes for a protein of 628 amino acids. Mature ABF A consists of 603 amino acid residues with a deduced molecular weight of 65.4 kDa and a theoretical pl of 3.7. For this ABF, an apparent pi of 3.3 and an apparent molecular weight of 83 kDa, determined upon SDS-PAGE, were previously documented.

    Although the three enzymes are all active against (1->5)-α-glycosidic bonds betweenL-arabinofuranosides, ABF A, ABF B and ABN A are genetically unrelated. ABF A was found to be N -glycosylated whereas ABF B and ABN A were not - these enzymes are only O -glycosylated. For each gene, arabinaseoverproducing strains were generated by introducing multiple gene copies in A.niger or in A.nidulans uridine auxotrophic strains through co-transformation. Transformants were isolated upon primary selection for uridine prototrophy. Subsequent overproduction of the genes introduced was demonstrated in these recombinant strains upon growth on sugar beet pulp, both immunochemically and by assaying enzyme activity. abf A was shown to be expressed in the heterologous host A.nidulans, despite the absence of an abf A gene equivalent in this organism. High-copy number A.niger abf B transformants featured impaired secretion of other extracellular proteins upon growth on sugar beet pulp. ABN A overproduction was found to be limited to approximately five times the wild-type level in A.niger abn A transformants, but not in A.nidulans transformants. Such a limitation was not observed in case of the ABFs.

    In Chapters 5 and 6, the regulation ofL-arabinan degradation is addressed. The structural genes seem to be regulated mainly at the transcriptional level. Additional copies of either A13F-encoding gene in A.niger were shown to result in a reduction, but not in total silencing of the expression of the wild-type ABN Aencoding gene upon induction with either sugar beet pulp orL-arabitol ( Chapter 5 ). The reduction of the expression level of abn A correlated with the abf gene dosage. The repression effected by extra abf B gene copies was more stringent and more persistent than that elicited by additional abf A copies. Although observed with both inducers, these phenomena were more outspoken and more persistent on sugar beet pulp. Similar, but more moderate effects were observed towards the expression of the other abf gene in multiple copy abf A- and abf B-transformants. It was proposed that the abf genes titrate two distinct gene activators both involved in coordination of arabinase gene expression. However, the three genes were shown to respond differently upon a mycelial transfer toL-arabitol-containing medium, indicating that gene-specific factors are also involved. Four distinct sequence motifs were found in common in the promoter regions of the three genes. One of these elements is identical to the A.nidulans CREA-motif, which has been shown to mediate carbon catabolite repression on several A.nidulans enzyme systems. Arabinase expression in A.niger is known to be repressed in the presence ofD-glucose. Two other motifs are highly homologous to cAMP-responsive elements described in other organisms. For the fourth motif no functional analogues could be found, but the element was found to be present in several other fungal genes which are not involved inL-arabinan degradation at all. It is therefore likely that none of these common elements confer system-specific regulation.

    The presumed involvement ofL-arabitol in the induction process of fungal arabinases was further emphasized by the induction characteristics of an A. nidulans mutant unable to grow on the end-product ofL-arabinan degradation,L-arabinose, nor onL-arabitol ( Chapter 6).L-Arabitol is an intermediate ofL-arabinose catabolism in Aspergilli. This mutant was shown to lack NAD +-dependentL-arabitol dehydrogenase activity resulting inL-arabitol accumulation, both intracellularly and in the culture medium, wheneverL-arabinose is present. Upon submerged growth on various carbon sources in the presence ofL-arabinose, the mutant featured enhanced expression of the enzymes involved in extracellularL-arabinan degradation, and of those of the intracellularL-arabinose catabolism. The co-substrates on which the mutant secreted large amounts of arabitol simultaneously exhibited high arabinase expression and featured reduced growth.L-Arabitol secretion and enzyme production were also observed on a mixed carbon source ofD-glucose andL-arabinose, resulting in normal growth. Hence, in the presence ofL- arabinose, the carbon catabolite repression conferred byD-glucose in the wild-type, is overruled in the mutant.

    In Chapter 7 , ABN A is shown to have remote sequence similarity with four bacterial xylanolytic glycosyl hydrolases (three β-D-xylosidases and an endo-1,4-β-D-xylanase), three of which feature activity against para -nitrophenyl-α-L-arabinofuranoside. This synthetic compound is commonly utilized to assay potential ABF activity, whereas it is known to be an inhibitor of the fourth enzyme. The homology became evident only after multi pie-sequence alignments and hydrophobic cluster analysis. It was proposed that these enzymes share a binding site for a terminal non-reducing α-linkedL-arabinofuranosyl residue and that they all belong to glycosyl hydrolase family 43. Implications from these suggestions were discussed. The ABFs could not be assigned to an established glycosyl hydrolase family.

    Based on theL-arabinolytic system of the brown-rot fungus Monilinia fructigena, the sequence similarity found amongst ABF A and bacterial pullulan-degrading enzymes, and ABF expression levels under carbon starvation conditions and onD-glucose as the carbon source, distinct functions inL-arabinan and plant cell-wall degradation were proposed for ABF A and ABF B. ABF A would be essentially cell-wall associated and act to degradeL-arabinan fragments generated by ABN A. ABF B activity would be important for the primary release of small amounts ofL-arabinose which initiate induction of various endolytic systems to degrade plant cell walls, and thus function in substrate sensing. In line with these considerations, the involvement of other, not yet identified glycosyl hydrolases inL-arabinan degradation by A.niger was suggested.

    Induction and repression of arabinase gene expression are further discussed in Chapter 7 . The results of the studies in A.niger (Chapter 5) and A.nidulans (Chapter 6) were interpreted in a mutual context. The identity of the lowmolecular-weight compound directly responsible for induction of arabinase gene expression, was addressed. BothL-arabinose andL-arabitol are likely candidates to fulfil such a role. However, it was not possible to weigh the actual inductive capacities ofL-arabinose andL-arabitol due to their in vivo convertibility and the carbon catabolite repression elicited by the pentose. Competition for such a compound provides an alternative explanation for the phenomena observed in Chapter 5. The involvement of the transcriptional repressor CREA in arabinase gene expression is not limited to the direct repression of structural and regulatory genes of theL-arabinan-degrading system. It also plays a role in inducer exclusion and end-product repression, two processes shown to be eminently involved in the regulation ofL-arabinan degradation in wild-type A.nidulans. Fungal growth rate was suggested to be related to derepression of theL-arabinan-degrading system. The possible involvement of cAMP in arabinase gene expression, as suggested by the presence of potential cis -acting cAMP-responsive elements in the structural genes, was considered. Various ways by which cAMP might modulate arabinase synthesis were surveyed.

    Rhizosphere carbon fluxes in field-grown spring wheat : model calculations based on 14C partitioning after pulse-labelling
    Swinnen, J. ; Veen, J.A. van; Merckx, R. - \ 1994
    Soil Biology and Biochemistry 26 (1994)2. - ISSN 0038-0717 - p. 171 - 182.
    koolhydraten - koolstof-stikstofverhouding - cellulose - decompositie - modellen - onderzoek - bodem - carbohydrates - carbon-nitrogen ratio - cellulose - decomposition - models - research - soil
    Knowledge on the quantity and dynamics of rhizodeposition under ecologically realistic conditions may elucidate various aspects of soil organic matter dynamics. Data from a field experiment with 14C pulse-labelling of spring wheat at different development stages, were used to estimate rhizosphere carbon fluxes. Not only the flux of C to the roots was assessed but also the fluxes of organic and inorganic release of root-derived material. C fluxes were calculated from curves fitted to data on shoot and root biomass and to data on 14C distribution at different development stages. The 14C distribution curves were extrapolated from the first labelling date (elongation stage) down to crop emergence and from the last labelling date (dough ripening stage) up to crop harvest, using different extrapolation procedures. The results show that while the maximum shoot growth rate occurred around ear emergence, the flux of C to the roots had a maximum around tillering. Over the entire growing season, shoot growth amounted to 5730 kg Cha−1 and 2310 ± 90 kg C ha−1 was translocated belowground. Of this 920± 150 kg C ha−1 was lost in root respiration and 500 ±120 kg C ha−1 was released as young photosynthate rhizodeposits, which are defined as organic materials released from the roots within 19 days after assimilation. Root growth amounted to 940 ±40 kg C ha−1, of which, however, 370 ±40 kg C ha−1 was lost again through root decay. Root turnover during the growing season, defined as root decay divided by root growth, was therefore 37–42%. Most of the organic input to soil (56–64%) occurred through rhizodeposition, while 36–44% was comprised in root biomass at crop harvest. The model used for the calculation of the carbon fluxes is discussed.
    14C pulse-labelling of field-grown spring wheat : an evaluation of its use in rhizosphere carbon budget estimations
    Swinnen, J. ; Veen, J.A. van; Merckx, R. - \ 1994
    Soil Biology and Biochemistry 26 (1994)2. - ISSN 0038-0717 - p. 161 - 170.
    koolhydraten - koolstof-stikstofverhouding - cellulose - decompositie - bodem - carbohydrates - carbon-nitrogen ratio - cellulose - decomposition - soil
    uantitative data on rhizodeposition under ecologically realistic conditions are scarce. Yet they are necessary to understand various aspects of soil organic matter dynamics. To evaluate the use of i4C pulse-labelling for rhizosphere carbon budget estimations and to develop a standard labelling procedure, the dynamics of 14C partitioning and factors affecting the representativity of the assimilated r4C for the average daily assimilation were investigated. Field-grown spring wheat plants were pulselabelled with i4C at five different development stages between elongation and dough ripening. Allocation of 14C in shoot tissue and soil-root respiration was complete by day 19 after labelling. The distribution of net fixed i4C was not affected by the time of day when labelling was performed. Therefore, net assimilated i4C was representative for the average daily net assimilation. The proportion of net fixed i4C recovered in the shoot increased from 61% at elongation to 85% at dough ripening. In the roots this proportion decreased from 15 to 2% and in soil-root respiration from 14 to 7%, while in the soil organic C the percentage did not change with the development stage. 14C in roots and soil organic C decreased exponentially with depth. We can conclude that i4C pulse-labelling of wheat plants with an allocation period of about 3 weeks is a satisfactory method to estimate assimilate distribution at different development stages.
    De relatie tussen glucosetolerantie bij hoogdrachtige zeugen en biggensterfte in de eerste week na werpen
    Kemp, B. ; Spoorenberg, J. ; Vesseur, P. - \ 1994
    Praktijkonderzoek varkenshouderij 8 (1994)1. - ISSN 1382-0346 - p. 23 - 23.
    diervoedering - koolhydraten - ontwikkeling - voer - groei - monosacchariden - voeding - biggen - zeugen - diergeneeskunde - animal feeding - carbohydrates - development - feeds - growth - monosaccharides - nutrition - piglets - sows - veterinary science
    Uit de humane geneeskunde is bekend dat zwangere vrouwen naarmate de zwangerschap vordert in toenemende mate intolerant worden voor glucose uit het dieet (de suiker uit het dieet niet goed kunnen verwerken). Dit kan in ernstige gevallen leiden tot zwangerschapssuikerziekte. Indien deze suikerziekte niet behandeld wordt kan dit leiden tot geboorteproblematiek en zelfs sterfte van het pasgeboren kind.
    Xylose metabolism in Bacteroides xylanolyticus X5-1
    Biesterveld, S. - \ 1994
    Agricultural University. Promotor(en): A.J.B. Zehnder; A.J.M. Stams. - S.l. : Biesterveld - ISBN 9789054852308 - 119
    bacteriën - anaërobe micro-organismen - micro-organismen - biochemie - metabolisme - synthese - koolhydraten - cellulose - celmembranen - celwanden - bacteria - anaerobes - microorganisms - biochemistry - metabolism - synthesis - carbohydrates - cellulose - cell membranes - cell walls

    Plant cell walls represent a major part of the available biomass on earth. They are mainly composed of the energy-rich polymers lignin, cellulose, and hemicellulose. For many decades, research is done to exploit agricultural and forestry wastes as renewable resources. Much research was focused on the degradation of cellulose. In contrast, hemicellulose. has got less attention, though it can account for up to 40% of the total dry weight of plant cell walls. Fermentation by anaerobic bacteria offers the possibility to conserve most energy fixed in the energy-rich polymeric and monomeric sugars in the form of organic acids and solvents (e.g. acetic acid, butanol and acetone).

    A project in which the anaerobic conversion of hemicellulose to potentially biotechnological interesting products was investigated, was divided into two parts. One part, performed by Philippe Schyns, concerned the microbial degradation of xylan, which was used as a model substrate for hemicellulose. Several xylanolytic enzymes (endo-xylanase, β-xylosidase, acetylesterase, α-L-arabinofuranosidase) were purified and characterized. The mode of action of some of these enzymes was investigated. Furthermore, the induction mechanism of xylanase and β-xylosidase was studied. The results of this research will be presented in a separate thesis. The other part of the project, of which the outcomes are given in this thesis, was focused mainly on the fermentation of xylose, a major constituent of hemicelluloses.

    Bacteroides xylanolyticus X5-1 was used as a model organism. This organism had been isolated from fermenting cattle manure. B. xylanolyticus X5-1 can only grow on one specific hemicellulose, xylan. Cellulose and other hemicelluloses could not be utilized for growth. This fact made the organism interesting for studying the (regulation of the) xylanolytic enzyme synthesis, since interferences from other (hemi)cellulolytic enzymes could be excluded. In addition, the organism could ferment a wide variety of monomeric sugars, produced a mixture of end products, and showed a relatively high growth rate. These latter features made B. xylanolyticus X5-1 a suitable microorganism for studying the regulation of the anaerobic xylose fermentation.

    Information concerning the composition and degradation of biomass, and the (regulation of) product formation from biomass has been reviewed in a general context in chapter 1. Some biotechnological applications of biomass fermentation have been mentioned in this chapter as well.

    Using 14C-labelled xylose, the xylose uptake system of this organism was studied. It was shown that xylose transport occurs via an active uptake system, and probably a binding protein was involved. The exact mechanism of xylose uptake remains to be elucidated. Based on mass balance calculations, measuring specific enzyme activities of key enzymes of catabolic pathways, and determining label distribution patterns with 13C-NMR, the pentose phosphate pathway in conjunction with the glycolysis was shown to be operative in xylose fermentation by B. xylanolyticus X5-1. Acetate, ethanol H 2 , CO 2 and formate were the main end products formed during xylose metabolism. At higher xylose concentrations, lactate and 1,2-propanediol were produced in small amounts as additional products. Reducing equivalents formed during the oxidation of glyceraldehyde-3-PO 4 and pyruvate, were used for the production of H 2 , formate, and ethanol. According to the proposed pathway about 2.5 mol of ATP, synthesized at substrate level, were generated per mol of xylose degraded. This part of the research is presented in chapter 2.

    The degradation of mixtures of hexoses and pentoses by B. xylanolyticus X5-1 is described in chapter 3. Batch culture cells did not show diauxic growth or a substrate preference for either glucose, xylose, arabinose or rhamnose, independent of the substrate the organism was grown on. In contrast, glucoselimited continuous culture cells were not able to consume xylose, unless some glucose or pyruvate was present as additional substrate. Glucose-limited continuous culture cells exhibited low activities of xylose transport and of xylose isomerase. Xylulose kinase could not be detected at all. Upon addition of xylose as single substrate to the glucose grown cells no increase in the transport rate and the isomerase and kinase activities was observed. However, when together with the xylose some glucose was added, all activities were induced. In the presence of chloramphenicol, an inhibitor of protein synthesis, xylose isomerase and xylulose kinase were not induced. The transport activity increased in a similar fashion as in the absence of chloramphenicol, suggesting that the transport system had to be activated and not induced. These experiments showed that i) xylose isomerase and xylulose kinase were regulated at the level of protein synthesis, ii) xylose transport was constitutively present, and iii) apparently, the glucose grown cells were carbon and energy limited. When grown under non-limiting conditions, as will probably happen in hemicellulose hydrolysates, B. xylanolyticus X5-1 can use sugar mixtures. This certainly is of biotechnological relevance, as conversion of the major substrate xylose will not be negatively affected by the minor, often preferred substrate glucose.

    Chapter 4 describes the effect of a low partial hydrogen pressure on the xylose metabolism in B. xylanolyticus X5-1. When grown in pure culture in the chemostat with xylose as the growth limiting substrate, B. xylanolyticus X5-1 produced acetate, ethanol, H 2 and CO 2 as the only end products. When grown in the presence of the methanogen Methanospirillum hungatei JF-1, xylose was converted to mainly acetate and CO 2 and presumably H 2 . Due to the cocultivation an increased biomass production was observed. H 2 could hardly be detected because it was efficiently converted to CH 4 by the methanogen. Ethanol was no longer produced. This type of regulation of product formation has been observed in many anaerobic microorganisms. However, xylose fermentation in B. xylanolyticus X5-1 was not only regulated at product level, but also on enzyme level. In cell free extracts of the pure culture of B. xylanolyticus X5-1 NAD and NADP-linked acetaldehyde and ethanol dehydrogenases could be detected. When grown in mixed culture with M.hungatei JF-1 these enzymes were no longer observed. The NAD and NADP-linked dehydrogenases were induced sequentially, when the interspecies electron transfer was inhibited, unless chloramphenicol was present. These results showed that product formation at low partial hydrogen pressure in B. xylanolyticus X5-1 is regulated at the level of enzyme synthesis.

    Several environmental conditions were used to affect xylose metabolism of B. xylanolyticus X5-1 ( chapter 5 ). Growth under a hydrogen atmosphere did not affect the xylose metabolism significantly. CO inhibited H 2 production from xylose completely with formate and ethanol as major reduced products. An increased ethanol yield resulted in a reduced amount of acetate and biomass formation. Xylose metabolism could also be affected by using alternative electron acceptors such as acetol, acetone, acetoin, and dihydroxy acetone. They were reduced to their corresponding alcohols 1,2-propanediol, 2-propanol, 2,3-butanediol, and glycerol, respectively. With these electron acceptors mainly acetate and CO 2 were formed and hardly any H 2 , formate and ethanol. As a result of more acetate formation, biomass production increased. In continuous culture with xylose as growth limiting substrate and acetol as electron acceptor, product formation from xylose shifted to mainly acetate and CO 2 as well. Acetol was not only reduced to 1,2-propanediol, but also converted to acetone. In gel activity staining of the alcohol dehydrogenases revealed that i) the NADP-linked ethanol dehydrogenase was repressed in the xylose + acetol grown culture, ii) the NADP-linked ethanol dehydrogenase in the xylose grown cells exhibited a nonspecific activity for both ethanol and 1,2-propanediol, and iii) another, also NADP-linked, 1,2-propanediol dehydrogenase was induced in the xylose + acetol grown cells.

    The data presented in this thesis show that it is possible to modulate the xylose metabolism of B. xylanolyticus X5-1 by several methods and at different levels during metabolism. The outcomes of this research might be applicable for other microorganisms of biotechnological value as well. Accordingly, the results can be used for biotechnological production processes and the biotechnological formation of valuable products (e.g. microbiological reduction processes, optically active products, enzymes like (stereospecific) alcohol dehydrogenases).

    Oligosacchariden als bifidogene factoren.
    Hartemink, R. ; Nout, M.J.R. ; Rombouts, F.M. - \ 1994
    Voedingsmiddelentechnologie 27 (1994)20. - ISSN 0042-7934 - p. 27 - 29.
    bifidobacterium - koolhydraten - chemische reacties - microbiële afbraak - polysacchariden - structuur - carbohydrates - chemical reactions - microbial degradation - polysaccharides - structure
    Levende bacterien die een gunstige invloed hebben op de darmflora. Ze worden probiotica genoemd en ze worden toegepast in zowel de humane voeding als de veevoeding
    Tailor-made produktie van oligosacchariden.
    Laere, K.M.J. van; Schols, H.A. ; Voragen, A.G.J. - \ 1994
    Voedingsmiddelentechnologie 27 (1994)20. - ISSN 0042-7934 - p. 33 - 35.
    koolhydraten - chemische reacties - chemische structuur - chemicaliën - voedselindustrie - voedseltechnologie - polysacchariden - eigenschappen - structuur - invloeden - carbohydrates - chemical reactions - chemical structure - chemicals - food industry - food technology - polysaccharides - properties - structure - influences
    De gewenste oligosacchariden kunnen met behulp van specifieke enzymen en chromatografische technieken 'op maat' worden gemaakt
    Characterization and mode of action of enzymes degrading galactan structures of arabinogalactans
    Vis, J.W. van de - \ 1994
    Agricultural University. Promotor(en): A.G.J. Voragen. - S.l. : Van de Vis - ISBN 9789054852377 - 161
    koolhydraten - cellulose - celmembranen - celwanden - fermentatie - voedselbiotechnologie - enzymen - carbohydrates - cellulose - cell membranes - cell walls - fermentation - food biotechnology - enzymes

    Agricultural biomass consisting mainly of cellulose, hemicellulose and lignin, is a renewable source of fuels and chemicals. An interesting option is enzymic conversion of biomass to readily usable material. To improve the overall economics of enzymic conversion of biomass not only cellulose but also hemicelluloses have to be degraded to monomeric sugars (saccharification). The aim of the work presented in this thesis was to study saccharification of arabinogalactans, a subgroup of the hemicelluloses.

    Arabinogalactans (AGs) have been found in numerous higher plants. In most plants these arabinogalactans occur only in small amounts, with exception of Larix and Acacia species. Their role in maintaining cell wall rigidity is discussed in chapter 1).

    Chapter 2 discusses structural features of AGs, subdivided in arabino-β(1->4)-galactans (type I) and arabino-β(1->3,1->6)galactans (type II), and gives a brief overview of enzymes degrading galactan structures of AGs.

    In chapter 3 the alkaline extraction of type I AGs from potato fibre, onion powder and citrus pomace is described. The extracts appeared to be mixtures of various polysaccharides. The presence of arabinan in all of these extracts is likely. By means of graded ethanol precipitation a major fraction enriched in type I AG could be precipitated in 40% v/v ethanol (denoted as F40). Results indicated that the 1,4-linked galactan backbone of onion F40 was substituted at C 6 with single unit galactose side-chains and for potato F40 also with 1,5-arabinans. Citrus TF40, (F40 treated with an endoglucanase for removal of contaminating xyloglucan), was suggested to contain a 1,4-linked galactan substituted at C 6 with short arabinose or highly branched arabinan side-chains and single unit galactose side-chains. A type I AG extracted from soy meal with alkali may be substituted at C 6 to a small extent with appendages of arabinose and single unit galactose side-chains.

    A type II AG from green coffee beans was indicated to consist of 1,3- linked galactan backbone substituted at C 6 with sidechains of arabinofuranose and galactose (chapter 3). The presence of terminal mannose possibly substituted on the sidechains, indicates a more complex structure for this polysaccharide. Analysis of a commercially available type II AG from larch (stractan) showed that the side-chains consisted also of arabinopyranose residues and this AG was a more heavily branched polymer than coffee AG.

    Endo-1,4-β-D-galactanases involved in the bioconversion of type I AG were purified from experimental enzyme preparations derived from Aspergillus niger and A. aculeatus (chapter 4). Their molecular weights were 42-43 kD and maximal activities were measured at pH 4.0- 4.3 and 50-55 °C on de-arabinosylated potato AG. In absence of substrate the A. aculeatus endogalactanase showed less thermal stability than the A. niqer endo-galactanase. Both endo-galactanases, which were similar in their mode of action, were suggested to degrade type I AG according to a multiple attack mechanism. It appeared that a combination of endo-galactanase and endo-1,5-α-L-arabinanase exerted synergistic effects in the initial stage of degradation of the potato AG. The action of these enzymes resulted in an increase in the downward shift of the molecular weight distribution of the digest and increased amounts of galactose, galactobiose and galactotriose (chapter 4). No synergism was observed for a combination of endo- galactanase and arabinofuranosidase B.

    Chapter 5 describes the purification of a β-D-galactopyranosidase. This β-galactosidase showed maximal activity on PNP-β-D-galactopyranose at pH 5 and 50 °C and was stable up to 50 °C and in the range of pH 3.5 to 7. It released non-reducing terminal galactose residues from type I AGs but not from type II AGs. With respect to polymeric substrates the enzyme showed highest activity towards 1,4- linkages but was also able to release 1,6-linked single unit galactopyranose side-chains.
    Chapter 6 describes that the differences in structural features of type I AGs were reflected in the combinations of enzymes which exerted synergistic effects in degradation. In the degradation of onion and potato F40 synergism occurred in the initial stage of degradation for the endo-galactanase/β-D-galactosidase combination. In the degradation of potato F40 the endo-galactanase/endo-arabinanase combination exerted also synergistic effects. The β-D-galactosidase released single unit galactose side-chains from both substrates thereby improving the affinity for endo-galactanase. These results were consistent with the structural features of these substrates reported in chapter 3.

    The activity of β-D-galactosidase on oligomeric reaction products released by endo-galactanase also enhanced degradation of potato and onion F40. This synergism occurred only in degradation of soy AG and citrus TF40. In the degradation of citrus TF40 synergistic effects were exerted also by the endo-galactanase/arabinofuranosidase B and endo-galactanase/endo-arabinanase combinations.

    An exo-1,3-β-D-galactanase purified from an experimental enzyme preparation derived from A. niger preferentially degraded 1,3-β-D-galactans (chapter 7). Mainly galactose and 1,6-galactobiose were released as reaction products from partly de-arabinosylated coffee AG. Hydrolysis of coffee AG by this exo-galactanase was accompanied by formation of small amounts of several arabinogalacto-oligomers. This indicated a limited capability of this enzyme of bypassing branching points. Optimal activity was measured at pH 5.0 and 40 °C and thermal stability was found in the pH range of 2.5 to 7.5 and up to 45 °C

    In the enzymic degradation of coffee bean AG a combination of exo-galactanase and α-L-arabinofuranosidase B exerted synergistic effects. For a combination of exo-galactanase and endo-arabinanase no enhancement in degradation of this substrate occurred. None of these combinations showed activity towards a type II arabinogalactan from larch wood (chapter 7).

    In chapter 8 discusses the isolation of type I and II AGs, the purification procedure of the endo-1,4-β-D-galactanases, the properties and mode action of the purified galactan degrading enzymes, their role in saccharification of AGs and other fields of possible application of galactan degrading enzymes.

    Crop residue decomposition, residual soil organic matter and nitrogen mineralization in arable soils with contrasting textures
    Matus, F.J. - \ 1994
    Agricultural University. Promotor(en): L. Brussaard; A.P. Whitmore. - S.l. : Matus - 141
    bodemstructuur - organische stof - bodem - bodemchemie - koolstof-stikstofverhouding - cellulose - koolhydraten - decompositie - bodemtextuur - grondmechanica - deeltjesgrootteverdeling - soil structure - organic matter - soil - soil chemistry - carbon-nitrogen ratio - cellulose - carbohydrates - decomposition - soil texture - soil mechanics - particle size distribution

    To evaluate the significance of cropping, soil texture and soil structure for the decomposition of 14C- and 15N-labelled crop residues, a study was conducted in a sand and a clay soil under laboratory and field conditions. The distribution of residual 14C, residual 15N and microbial biomass 14C of different aggregate size classes and physical protection of soil organic matter as indicated by the rates of 14C and 15N mineralization after soil disaggregation were also studied in the same soils. Soil texture and soil structure were not determining factors in the decomposition of residual labelled soil organic matter, but residue type was important for N mineralization soon after incorporation. Recently formed labelled soil organic matter was less well physically protected than older soil organic matter and adsorption of soil organic matter on to silt and clay particles was the main mechanism of physical protection in sand soil. In clay soil the results were not conclusive as regards the main mechanism of protection of recently formed soil organic matter. In conclusion because soil structure broken up by soil disruption, and soil texture were found to have no effect on the rate of decomposition of recently formed organic matter in soil, we do not need to include these factors when the C and N mineralization from crop residues in arable soils has to be estimated.

    Influence of carbohydrates on feed intake, rumen fermentation and milk performance in high-yielding dairy cows
    Visser, H. de - \ 1993
    Agricultural University. Promotor(en): S. Tamminga. - S.l. : De Visser - 174
    voer - koolhydraten - melkvee - melkveehouderij - diervoedering - spijsvertering - melkproducten - zuivelindustrie - feeds - carbohydrates - dairy cattle - dairy farming - animal feeding - digestion - milk products - dairy industry

    Food for human consumption originates directly from plants, after processing, or indirectly by conversion of plant materials into food of animal origin through livestock. An important example of food of animal origin are dairy products such as milk, cheese, butter, yoghurt, etc.

    During the last decades milk production from Dutch dairy herds has increased considerably. This increase in production, yield and content, was the result of a combination of improvements in genetic potential, due to breeding and progress made in nutrition. Within the area of nutrition better quality roughage and increased usage of concentrates were at the root of this progress.

    Initially the concentrates were based mainly on grains and oil cakes. These feedstuffs showed, slight variation in energy and protein value. Large quantities of by-products, varying in origin, are produced as a consequence of food production. Without alternative use, these by-products would be wasted and as such provide an additional source of environmental pollution. Fortunately, many by-products of food production have considerable value as feedstuffs and are used in ruminant nutrition.

    For the profitable utilization of by-products in dairy cow feeding a precise evaluation of their feeding value is essential, because of the high degree of variation involved. Product classification according to the processing methods is a help, but considerable emphasis should be given to chemical composition and predictive methods of evaluation using this or alternative sources of information. Some of these by-products are produced using high moisture techniques. These products sometimes become available after artificially drying or are delivered with a high moisture content and have to be ensiled.

    One of the chemical components, which varies the most in by-products is the carbohydrate fraction. Sometimes, some of the carbohydrates (starch, sugars) are removed during processing, increasing the concentration of cell wall constituents, ash, fat and protein content in the remaining product. By selecting and combining various by- product ingredients, large variations in the carbohy drate composition of concentrates can be achieved, even when feeding isocaloric diets. Although these concentrates are similar in their energy value, the fermentation pattern in the rumen may differ widely. If the products contain large quantities of starch such concentrates may even cause rumen acidosis, because of their rapid fermentation and accumulation of lactic acid in the rumen. By replacing starch with highly digestible cell wall constituents the pattern changes in favour of more acetic acid instead of propionic and/or lactic acid. These changes in fermentation pattern had a positive influence on total DM intake, which resulted in an increase in milk yield (Chapter 2).

    In a subsequent study, comprising a feeding trial (Chapter 3) and fermentation study (Chapter 4) an investigation was made of the influence of the dry matter content of some concentrates (dried versus pressed ensiled beet pulp) and replacements of some concentrates with extra roughage (maize silage). Total DM intake was highest on the dried beet pulp diet. Milk production did not differ between treatments, as with fat yield and content. Milk protein yield and content tended to be lowest for the group fed maize silage. The rumen fermentation study showed similar concentrations of major VFA's on all diets. The concentration of branched-chain fatty acids and ammonia were highest for the cows fed maize silage, indicating reduced microbial protein synthesis, which confirmed the tendency towards lower milk protein yield measured in the feeding trial. The degradation characteristics of the OM showed the lowest rate with maize silage. The undigestible fraction (U) was highest with maize silage. The results of both experiments demonstrated the importance of the balance between energy and protein availability for rumen fermentation.

    Higher levels of intake caused an increase in the concentration of volatiles and reduced rumen fluid pH. Feed intake level influenced the pattern of consumption, which changed from an intake pattern of two large meals at low intake level, towards several smaller meals at the high level of intake. Although concentrations were highest at the high intake level, diurnal variation was highest on the low level of intake, due to the meal size.

    Grass silage can be fed as wilted or wet ensiled material. In the latter case some carbohydrates will be replaced by fermentation end products during the ensiling process, reducing the amount of easily fermentable carbohydrates and increasing the soluble fraction and rate of N degradation (Chapter 6). In a feeding trial (Chapter 5), in which a comparison was made between the DM content and the amount of fermentation end products, reduced DM intakes were found on diets low in DM content as well as those high in fermentation end products. The effects of DM content as such were minor, compared to those of the combination of low DM content and increased amounts of fermentation end products. Reduction in DM intake, due to a low DM content, was restricted to the first 6 weeks of lactation, whereas the combination effect remained throughout the experiment. Total DM intake was lowest for high moisture diets, which was reflected in lower energy and protein intakes. Milk production was lowest on high moisture diets, reflecting the lower energy intake. Milk fat content and yield were not affected, partly because of the increased mobilization of body fat during the period of negative energy balance. Milk protein content and yield were lowest on high moisture diets. The fermentation and kinetic studies (Chapter 6) showed reduced pH and increased concentrations of total VFA, acetic acid, ammonia and BCFA on high moisture diets. The rates of clearance of the OM fraction were significant or showed a tendency towards lower values for high moisture diets, which agreed with the lower total DM intake found in the feeding trial. These results were negatively influenced by the type of concentrates fed in both experiments, a very low amount of easily fermentable carbohydrates were fed (ensiled by-products low in starch and sugars). Animals fed these diets were unable to balance the availability of nitrogen and energy for microbial protein synthesis. This resulted in a lower yield of milk protein and a reduction in milk protein content.

    An attempt was made to compare the effects on feed intake and milk performance of the type of carbohydrate (starch versus cell wall constituents) and rate of degradation (rapidly versus slowly). This was performed in a feeding trial (Chapter 7) accompanied by fermentation and kinetic studies (Chapter 8). Starch reduced milk fat content, which in the case of rapidly fermentable starch can be explained by a decrease in the ratio of non- glucogenic to glucogenic volatile fatty acids (NGR) found in the rumen. The shift from fermentation in the rumen towards digestion in the small intestine, increase in by-pass starch, partly eliminated the lower NGR in the rumen, but the total amount of glycogenic precursors was found to be higher in animals fed by-pass starch. Milk fat content was highest from animals fed high levels of cell wall constituents. Milk protein content was highest on both starch diets, while the diets rich in cell wall constituents displayed the lowest values. Rumen fermentation characteristics showed an increase in the concentration of ammonia and BCFA and a tendency towards lower amounts of microbial protein in the rumen, which confirmed the results of the feeding trial. Differences occurred between both cell wall diets, because one of these diets did not have an optimal balance between cell wall and nitrogen degradation rates.

    In the general discussion (Chapter 9) an attempt is made to predict feed intake, milk yield (lactose), milk fat and milk protein production. Different models were used to predict the total DM intake as measured in the feeding trials. Relationships were poor, when predicting DM intake using the energy requirements and the energy density per kg DM. Relationships were improved when body weight, stage of lactation and percentage concentrate in the diet were included as independant variables. Results were much improved, when DM intake was predicted by means of equations derived from rumen kinetic parameters. However, all predictions were poor for diets with a dry matter content below 35 percent. This was due to the lower intake measured during the first weeks of lactation, and to the fact that these types of diets were not included in the data set, from which the equations were derived. An attempt was made to estimate the production of nutrients using a rumen fermentation model. Differences in predicted nutrient supply occurred between the diets fed in the different experiments described in the various chapters. The major differences were found between starch-rich diets and diets rich in cell wall constituents in the amount of glycogenic precursors (propionate and glucose) and from the total level of feed intake, which increased the amount of propionic acid produced in the rumen. Relationships between rumen fermentation parameters (NGR) and milk fat content were adequate within experiments. However, relationships between experiments were poor. Large between treatment differences were found in the amount of ketogenic precursors available for milk fat production from mobilization of body reserves. Estimation of the amount of milk fat produced from rumen ketogenic nutrients (acetic and butyric acid) by de novo synthesis and the production of ketogenic nutrients in the rumen predicted by the model showed a good relationship. Differences between total milk fat production and de novo synthesis could be explained by the availability of longchain fatty acids (LCFA) available to the animal directly from the feed or from mobilization of body reserves. Milk protein was related to the amount of DVE available for milk production. The DVE intake between treatments was related to the microbial protein synthesis in the rumen and could be explained by the balance between nitrogen and energy sources. Milk lactose was related to the availability of glycogenic precursors and showed a very low variation between treatments indicating that the high yielding dairy cow in early lactation is probably hormonally geared towards the production of milk lactose, which might even be preferred above the production of milk protein, due to gluconeogenesis. Although the results of the feeding trials could be explained afterwards from the total energy intake, milk production and milk composition and the deposition and/or repositioning of body reserves, prediction of milk yield and composition was impossible. However, when including the chemical composition of the diets, its rate of degradation, the kinetics of the dietary ingredients and the extent of deposition and reposition, it became possible to predict milk production and composition.

    In conclusion it can be stated that milk composition could be explained reasonably well from the estimated supply of individual nutrients. However, it should be realised that more information is required concerning the partitioning of nutrients to the various tissues in the animal, and the relationships involved with fermentation and digestion before evaluation based on net energy (VEM) and protein absorbed from the small intestine (DVE) can be replaced by more accurate predictive methods for practical use.

    Enzymatic synthesis of polyol seters in aqueous - organic two-phase systems
    Janssen, A. - \ 1993
    Agricultural University. Promotor(en): K. van 't Riet. - S.l. : Janssen - ISBN 9789054851271 - 181
    emulgeermiddelen - chemische reacties - synthese - carboxyl ester hydrolasen - tannase - choline esterase - triacylglycerol lipase - koolhydraten - vetzuren - carbonzuren - emulsifiers - chemical reactions - synthesis - carboxylic ester hydrolases - tannase - cholinesterase - triacylglycerol lipase - carbohydrates - fatty acids - carboxylic acids

    The last decade increasingly attention is paid to lipases as catalysts for synthesis of components, such as fatty acid-based surfactants, flavors, edible oil equivalents, monomers and polymers, and amides. In this thesis, the lipase-catalyzed esterification of polyols and fatty acids is described. These esters consist of a nonpolar part (fatty acid) and a polar part (polyol). Therefore, polyol esters have surface-active properties and are used as emulsifier in food, pharmaceutics; and cosmetics. One of the aims of this thesis is to develop a reaction system for the esterification of polyols (carbohydrates) and fatty acids, without any modification of the substrates. Also, high reaction rates are desired.

    Enzymatic esterification is often performed in the presence of organic solvents. Besides activity and stability of the enzymes, the solvents will affect the equilibrium position of reactions. In literature, models were described for the prediction of the equilibrium position in dilute two-phase systems. However, for industrial applications, high product concentrations are desired, which implicate the use of nondilute reaction systems. Another aim of this thesis is to gain a better insight in factors that affect the equilibrium position of a reaction and to predict the product concentrations at equilibrium in non-dilute two-phase systems.

    In chapter 2 and 3, the lipase-catalyzed esterification of sorbitol and fatty acid is studied in two different two-phase reaction systems. In chapter 2, 2-pyrrolidone is used as a cosolvent for sorbitol. In this study, the lipase from Chromobacterium viscosum is used and the initial esterification rate is high as compared to literature data. The water activity is found to be important for the ester concentrations at equilibrium. High concentrations of the cosolvent 2-pyrrolidone should be avoided, because these will inactivate the lipase. In the reaction system that is described in chapter 3, water is used to dissolve sorbitol. Candida rugosa lipase is used in this study and initial esterification rates are slightly higher than in chapter 2. The water activity is dependent on the sorbitol mole fraction in the aqueous phase and lowering of the water activity is limited by the solubility of sorbitol. A two-phase membrane reactor is a suitable type of reactor, since the water activity of the aqueous phase can be kept constant during the experiment and lipase possesses a good stability. In both reaction systems, besides sorbitol also glucose and fructose can be used as a substrate, while disaccharides, such as sucrose, are not reactive at all.

    In chapter 4, the lipase-catalyzed esterification of glycerol and decanoic acid has been studied in aqueous-organic two-phase systems. The addition of an organic solvent is found to influence the ester mole fractions at equilibrium. For the synthesis of polar products (monoesters), a polar solvent (low log P) is favorable, while for the synthesis of nonpolar products (triesters), it is better to choose a nonpolar solvent (high log P). The computer program 'Two-phase Reaction Equilibrium Prediction' (TREP) has been developed for the prediction of the ester concentrations in nondilute two-phase systems, in case both the reaction equilibrium as well as the phase equilibrium are achieved. This program is based on mass balances and the UNIFAC group contribution method. Deviations in the prediction with TREP are generally less then a factor of 2 and are due to inaccuracies of the UNIFAC group contribution method.

    The lipase-catalyzed acylglycerol synthesis with fatty acids of different chain length is studied in chapter 5. For predictions with TREP, one set of equilibrium constants is used for monoester, diester, and triester synthesis. It is shown that with this set the equilibrium position of the reaction between glycerol and all saturated fatty acids with a chain length from 6 to 18 and oleic acid can be calculated within some margins. For fatty acids with different chain length, the ester mole fractions at equilibrium are clearly different. With the short-chain hexanoic acid, the monoester mole fraction is highest, while for the long-chain oleic acid, the diester mole fraction is the highest one. Besides the equilibrium position, also the reaction rates are affected by the solvent that is added. In polar solvents, the monoester production rate is enhanced. This is caused by the shift in the equilibrium mole fractions.

    In chapter 6, the effect of solvents on the esterification of decanoic acid and several alcohols, such as 1-dodecanol, 1-butanol, 1,3-propanediol, and sorbitol is studied. In agreement with the previous results, the ester mole fractions at the reaction equilibrium are dependent on the solvability of the ester in the organic phase. This effect is most striking for the polar sorbitol esters. Almost no esters are present at equilibrium in systems with nonpolar solvents, while reasonable high ester mole fractions can be obtained in systems with polar solvents. In contrast with the results of chapter 5, the equilibrium constants are clearly affected by the type of alcohol that is chosen as a substrate. Calculations with TREP showed that the calculated ester mole fractions did not deviate more than a factor of 1.5 from the measured ones. However, it appears that the calculated water mole fractions deviate systematically in the downwards direction.

    Chapter 7 shows a comparison between models in literature for the prediction of the equilibrium position in dilute two-phase reaction systems and calculations with TREP. It is shown that the models from literature are limited to reaction systems in which partition coefficients are constant. The program TREP can be used for nondilute as well as dilute reaction systems.

    Furthermore, this chapter shows that the ester mole fractions at equilibrium can be increased with increasing temperature. This is due to the increase of the solubility of sorbitol with increasing temperature. Most pronounced is the effect of temperature on the reaction rate, which is increased enormously. However, for long-term processes at high temperatures it is important that heat-stable lipases will be used.

    Characterisation and enzymic degradation of non-starch polysccharides in lignocellulosic by-products : a study on sunflower meal and palm-kernel meal
    Duesterhoeft, E.M. - \ 1993
    Agricultural University. Promotor(en): A.G.J. Voragen, co-promotor(en): W. Pilnik. - S.l. : Duesterhoeft - ISBN 9789054850762 - 134
    lignocellulose - lignine - zonnebloemolie - asteraceae - plantaardige oliën - palmpitolie - helianthus annuus - zonnebloemen - elaeis guineensis - oliepalmen - fermentatie - voedselbiotechnologie - bijproducten - koolhydraten - cellulose - celmembranen - celwanden - lignocellulose - lignin - sunflower oil - asteraceae - plant oils - palm kernel oil - helianthus annuus - sunflowers - elaeis guineensis - oil palms - fermentation - food biotechnology - byproducts - carbohydrates - cellulose - cell membranes - cell walls

    Non-starch polysaccharides (NSP) constitute a potentially valuable part of plant by- products deriving from the food and agricultural industries. Their use for various applications (fuel, feed, food) requires the degradation and modification of the complex plant materials. This can be achieved by enzymatic processes which, in comparison with chemical or physical methods, are regarded as energy-saving and non-polluting. However, a major disadvantage of enzymic processes often is their low effectivity and consequently high costs.

    The investigations described in this thesis were conducted to understand the reasons for the low susceptibility to enzymic hydrolysis of such by-products and, in particular, of their non-starch polysaccharides, and to find out whether and how the efficacy of enzymic treatment could be enhanced. The studies should provide information necessary for the development of polysaccharidase-preparations, tailored for the use in different applications.

    Sunflower ( Helianthus annuus L.) meal and palm-kernel ( Elaeis guineensis Jacq) meal, by-products from the production of edible oil and used as animal feed compounds, were chosen for our studies.

    In chapter 1 an introduction is given to the macroscopic and microscopic structure of the raw materials, to plant cell walls and their constituent polymers. The biodegradation of cell walls and its limitations are briefly reviewed and major non-starch polysaccharide degrading enzymes are summarised. Chapter 1 closes with an outline of the thesis.

    For a detailed study of type and structure of the non-starch polysaccharides, cell wall materials (CWM) were prepared from the meals by enzymatic digestion of protein and removal of small amounts of buffer-extractable material ( chapter 2 ). The resulting CWM's were enriched in NSP (55% of sunflower CWM and 75% of palm-kernel CWM) and had a high lignin content. Two different chemical methods, sequential extraction with alkali and sodium chlorite and treatment with 4-methylmorpholine-N-oxide (MMNO) were tested to extract all constituent polysaccharides. Almost complete dissolution could be achieved by a combination of both methods, but the recovery of sugars, especially during MMNO treatment, was low. From the sugar composition of polysaccharide fractions, obtained by sequential chemical extraction, a tentative identification of major polysaccharides was achieved. Their distribution in different botanical fractions of the meals could be deduced by comparison with data from literature (sunflower) or by own experiments (palm-kernel).

    The polysaccharide extracts of different purity were further fractionated by graded precipitation with ethanol, size-exclusion or adsorption-chromatography. By determination of the sugar- and glycosidic linkage composition of extracts, (partially) purified subfractions and intact cell wall materials, the identification, partial characterisation and quantification of major non-starch polysaccharides were achieved ( chapter 3 ). In sunflower meal, cellulose (42% of NSP), pectic polysaccharides (24%) and (4-O-methyl)-glucuronoxylans (24%) with about 10% glucuronosyl-substitution were major constituents. Minor amounts of (gluco)mannans (5%) and fucoxyloglucans (4.5%) were also identified. Major polysaccharides in palm-kernel meal were mannans (78% of NSP) with very low degrees of galactose-substitution and of apparently small molecular size (DP 12 to 14), and cellulose (12%). Arabinoxylans (3%) and (4- O -methyl)-glucuronoxylans (3%), deriving from the endocarp fraction of the meal, were present in low amounts in this monocotyledenous material.

    For a study of the enzymic hydrolysis of the cell wall materials ( chapter 4 ), three multi-component enzyme preparations were chosen. Solubilisation occurred as a bi-phasic process with high reaction velocities in the first stage of the incubation and only slow progress during extended incubation up to 72h. The solubilisation could markedly be improved by reduction in particle size; partial delignification or increasing enzyme concentration, however, had almost no effect. Maximally 30% of NSP in sunflower meal and 50% in palm-kernel meal could be solubilised from the finely milled CWM's. Although the composition of the enzyme preparations was found to influence the type of reaction products, the extent of their release and, as observed by transmission electron microscopy, the site of enzymic attack in different cell wall layers, our results suggested that substrate accessibility was the major factor limiting enzymic hydrolysis.

    A detailed study of the reaction products obtained by incubation with the crude enzyme preparations or fractions thereof (prepared by anion-exchange chromatography) revealed, that pectic compounds and mannose-containing polysaccharides in sunflower CWM were readily degradable ( chapter 5 ). The hydrolysis of mannans in palm-kernel CWM varied from 20% to 50%. In both CWM's, xylans and cellulose were most resistant to hydrolysis. The results indicate the preferential degradation of parenchyma and endosperm tissues and the resistance of hull and endocarp fractions to enzymic hydrolysis. The reaction products formed during all stages of the treatment were of small oligomeric and monomeric size.

    The contribution of different enzyme activities to the total solubilisation achieved by the heterogeneous enzyme preparations was studied with (partially) purified subfractions which were prepared by various chromatographic techniques from the crude preparations, and with highly purified enzymes from other microbial sources ( chapter 6 ). In general, the effect of these purified enzyme fractions was low (solubilisation of NSP: 1 % to 5 %). Supplementation of main enzyme fractions with pectolytic, cellulolytic or mannanolytic subfractions did only slightly enhance the total solubilisation. Synergistic action was observed between glucanases and mannanases in palm-kernel incubations and between arabinanases, polygalacturonases and rhamnogalacturonan-degrading enzyme fractions in the hydrolysis of pectic polysaccharides in sunflower CWM. The enzymic hydrolysis of (4- O -methyl)-glucuronoxylans was studied in-situ and with the isolated polysaccharide. The results indicated that the resistance of the xylans to enzymic degradation is not only due to their interlinkage with other polymers and location in the cell wall but also to their primary structure.

    In chapter 7 , important aspects concerning the approach and the methodology used are discussed. Implications arising for different fields of application are shown and suggestions for the formulation of enzyme preparations, which merit further research, are made.

    Structural characteristics of arabinoxylans from barley, malt and wort = Structuurkenmerken van arabinoxylanen uit gerst, mout en wort
    Vietor, R.J. - \ 1992
    Agricultural University. Promotor(en): A.G.J. Voragen, co-promotor(en): S.A.G.F. Angelino. - S.l. : Vietor - 127
    moutgerst - bierbereiding - graansoorten - mouten - mout - hordeum vulgare - gerst - koolhydraten - analyse - chemie - analytische scheikunde - malting barley - brewing - cereals - malting - malt - hordeum vulgare - barley - carbohydrates - analysis - chemistry - analytical chemistry

    Flours from dehusked barley and malt were fractionated to obtain water-insoluble cell wall material (WIS). A mass balance of these fractionations was determined. Arabinoxylans were extracted from this WIS in high purity and yield with Ba(OH) 2 , and subfractionated with graded ethanol precipitation.

    The structural elements present in these arabinoxylans and in arabinoxylans isolated from wort were determined. These arabinoxylans all consisted of a backbone of (1-->4)-linked β-D-xylopyranose units (Xyl p ), a proportion of which were substituted with alfa-L- arabinofuranose (Ara f ) at O-2 and/or O-3 of the Xyl p units. A new feature was the presence in barley and malt arabinoxylans of a large amount of Xyl p units carrying a single Ara f substituent at O-2. The amounts of Xyl p substituted at O-2 or at both O-2 and O-3 increased with increasing substitution of the xylan backbone. The wort arabinoxylans were found to be exceptionally rich in O-2,3-disubstituted Xyl p .

    A number of fragments could be isolated after degradation of barley and malt arabinoxylans with endoxylanase 1 from Aspergillus awamori . The structures of the isolated fragments were determined. From the structures found, it could be shown that the position of Ara f substituents on the xylose residues of the arabinoxylan influenced the extent of enzymic degradation of the xylan backbone, substituents at O-2 being more efficient than substituents at O-3 with the enzyme used. From these data and the linkage composition of undegradable arabinoxylan fractions, it was concluded that the distribution of Ara f substituents over the xylan chain was not random, but fairly regular.

    The arabinoxylans extracted from barley and malt cell wall material appeared to be very similar in composition and structural features. This implies that changes during malting are small or extremely localized.

    Cationic starches on cellulose surfaces : a study of polyelectrolyte adsorption
    Steeg, H.G.M. van de - \ 1992
    Agricultural University. Promotor(en): B.H. Bijsterbosch; A. de Keizer. - S.l. : S.n. - 142
    adsorptie - sorptie - elektrolyten - zetmeel - koolhydraten - cellulose - celmembranen - celwanden - adsorption - sorption - electrolytes - starch - carbohydrates - cellulose - cell membranes - cell walls

    Cationic starches are used on a large scale in paper industry as wet-end additives. They improve dry strength. retention of fines and fillers, and drainage. Closure of the white water systems in the paper mills hase increased the concentration of detrimental substances. This might be the reason for the poor retention of cationic starches observed in the last few years.

    The purpose of the research described in this thesis was to obtain a better understanding of the adsorption of cationic starch on cellulose and how this interaction can be disturbed. In contrast to most research in papermaking we have used a colloid-chemical approach. This means that we kept our experimental system as simple as possible and therefore far from the reality of papermaking.

    In chapter 2 we tried to generalize the specific problem of cationic starch adsorption on cellulose to polyelectrolyte adsorption on an oppositely charged surface. We used a recent extension of the polymer adsorption theory of Scheutjens and Fleer for polyelectrolyte adsorption to perform model calculations. It emerged that, for the adsorption of a strong polyelectrolyte on an oppositely charged surface, two regimes can be distinguished based on the effect of salt concentration on the adsorption. We call these the screening-enhanced adsorption regime and the screening-reduced adsorption regime. In the former regime the adsorption increases with increasing salt concentration because the repulsion between the segments is screened and a nonelectrostatic interaction between polyelectrolyte and surface is present. The adsorption decreases with increasing salt concentration in the latter regime, because the mainly electrostatic attraction between polyelectrolyte and surface is screened. A transition between these two regimes can take place if the balance between the electrostatic and nonelectrostatic interactions is changed. The electrostatic interactions are determined by the segment charge and the surface charge density. The strength of the nonelectrostatic interaction is described with a χs parameter, the net adsorption energy in units kT. From the model calculations it appears that the screening-reduced adsorption regime always occurs if the interaction between polyelectrolyte and surface is only electrostatic (χs=0). The polyelectrolyte can then be completely displaced from the surface with salt ions. If there is a nonelectrostatic attraction between polyelectrolyte and surface (χs>0) the screening-enhanced adsorption regime shows up in most cases. Only for very low segment charges and not too low surface charge densities, which is often the case for polyelectrolytes used in papermaking, we are dealing with the screening-reduced adsorption regime. The theory also predicts that the adsorbed amount shows a maximum as a function of the segment charge, irrespective of the value of χs. For a very low salt concentration this occurs at a segment charge of about 0.01 unit charges, or even lower.
    If the counter ions have a specific interaction with the surface, the adsorption of a polyelectrolyte can pass through a maximum as a function of the salt concentration provided χs is not too small.
    The predictions of the model calculations agree very well with experimental results reported in literature.

    The careful characterization of the materials and the experimental methods we used are described in chapter 3. We showed that the microcrystalline cellulose, which we use as a model for cellulose fibers, is level-off DP cellulose. This means that we are dealing with fibers chemically cut into pieces. The microcrystalline cellulose had to be cleaned before use. because hemicellulose came off in aqueous solutions disturbing the determination of the equilibrium concentration of starch with a carbohydrate determination. This was accomplished by washing the microcrystalline cellulose with concentrated NaOH solutions. The surface charge of the microcrystalline cellulose, originating from carboxylate groups, was determined by potentiometric titrations to be about -1 C/g at pH=7, which is a little lower than reported for cellulose fibers. The specific surface area is a somewhat problematic quantity for a porous substrate as microcrystalline cellulose. Based on the adsorption of cationic polyelectrolytes with different molecular weights on microcrystalline cellulose, we estimated the accessible surface area for cationic starch to be about 6 m 2/g, which is only 10% of the surface area accessible to small ions.

    We used two different types of cationic starch, namely cationic potato starch and cationic waxy maize starch. Potato starch consists of two components, an essentially linear polymer of α-1,4 glucose, called amylose, and a much larger branched polymer, called amylopectin. The fraction of amylose is about 21%. Waxy maize starch consists of amylopectin. only. From their sedimentation coefficients we estimated the molecular weight of cationic amylose to be about 3.5.10 5and of cationic amylopectin from potato starch between 5.10 7and 5.10 8. The molecular weight of cationic amylopectin from waxy maize was estimated to be between 1.10 7and 6.5.10 7. Both cationic starches showed a marked decrease in viscosity and hydrodynamic radius, as measured by dynamic light scattering, with increasing electrolyte concentration. This indicates that cationic amylopectin has enough flexibility to shrink, even though it has a branched structure.
    Special attention is paid to the methods with which the starch concentration can be determined, especially to the well-known iodine determination. It is shown that it is very important to specify the iodine and iodide concentrations in the final solution with the blue starch-iodine complex and the wavelength at which the absorbance is measured.
    Finally we describe how the adsorbed amounts are measured by depletion.

    In chapter 4 we investigated the adsorption of cationic amylopectin (from waxy maize, DS(Degree of Substitution) =0.035) on microcrystalline cellulose in the presence of simple electrolytes and at different pH values. The adsorption isotherms of cationic amylopectin were all of the high affinity type, as is expected for polyelectrolyte adsorption. The plateau value of the adsorbed amount showed a maximum as a function of the salt concentration. It was also found that the adsorbed amount, in the region
    where it decreases with increasing salt concentration, was very sensitive to the type of cation used. We obtained a Iyotropic series for the alkali cations, where the adsorbed amount in the presence of the cations decreased as Li +>Na +=K +>Cs +. The trend of these experimental results could be explained very well with the theory on polyelectrolyte adsorption described in chapter 2.

    The plateau value of the adsorbed amount increased with increasing pH in the same way as the surface charge. The adsorbed amount of charge was estimated to be 10% of the titratable surface charge.

    Based on the dependence of the adsorption on the pH and the salt concentration, we concluded that for cationic amylopectin charge interactions are the main driving forces for adsorption on cellulose.

    The adsorption of cationic potato starch (usually DS=0.035) on microcrystalline cellulose is investigated in chapter 5. Special attention is paid to the fact that cationic potato starch is a mixture of 21% amylose and 79% amylopectin. It was found that amylose adsorbs preferentially. This was attributed to a larger accessible surface area for amylose due to its ability to enter the pores of microcrystalline cellulose during the equilibration time (15 hours).

    The adsorption isotherms of cationic potato starch are also of the highaffinity type. There is a strong dependence on the cellulose concentration, caused by heterodispersity of the amylose and the amylopectin fractions.

    The adsorption of cationic potato starch strongly and monotonously decreased with increasing salt concentration. It was completely displaced by salt ions at concentrations larger than 0.05 M. The divalent cations Ca 2+and Mg 2+appeared to be ten times as effective as Na+ in suppressing the adsorption of cationic potato starch, which is due both to their higher charge and a specific interaction with the cellulose surface. From the small difference in effect of Ca 2+and Mg 2+we concluded that the phosphate groups in cationic Potato starch play no relevant role in the adsorption.

    Increasing the pH led to increasing adsorption. The adsorbed amount of charge was estimated to be 10% of the titratable charge.
    Finally, we investigated the effect of DS on the adsorption of cationic potato starch. At 2 mM NaCl the adsorbed amount of the starch with the lowest DS (0.017) was largest, but at 10 mM NaCl the difference between starches with DS=0.017, 0.035 and 0.047 was very small. The adsorbed amounts decreased slightly with decreasing DS. Theory on polyelectrolyte adsorption predicts that at a salt concentration of about 0.01 M the adsorbed amounts of polyelectrolytes with various segment charges can be the same indeed. The effect of segment charge is larger at lower and higher salt concentration. At a low salt concentration the starch with the lowest DS is expected to adsorb most, whereas at high salt concentration the starch with the highest DS will adsorb best.
    We concluded from the strong dependence on salt concentration and pH that the adsorption of cationic potato starch on cellulose is mainly driven by electrostatic attraction.

    In chapter 6 we conclude that the adsorption of cationic starch on cellulose is mainly determined by the presence of charges and not by certain special properties of starch and cellulose. We point out that this thesis has general relevance because of the new light it sheds on polyelectrolyte adsorption. For papermaking this thesis is particularly relevant, because it explains the adsorption behaviour of cationic starch as that of polyelectrolytes and it therefore also improves the understanding of the adsorption of other polyelectrolytes used in papermaking. The adsorption behaviour of cationic potato starch is compared with that of cationic amylopectin from waxy maize. We suggest that this may be caused by differences in size and shape. Finally we indicate which results can be of direct relevance for papermaking in practice.

    Darmverteerbaar threonine belangrijk bij eiwitverlaging
    Lenis, N. ; Diepen, H. van - \ 1991
    Praktijkonderzoek varkenshouderij 5 (1991)2. - ISSN 1382-0346 - p. 18 - 20.
    koolhydraten - verteerbaarheid - voer - varkens - carbohydrates - digestibility - feeds - pigs
    In een onderzoek van het IWO op het Varkensproefbedrijf te Raalte is de threonine behoefte van vleesvarkens onderzocht, uitgedrukt op basis van darmverteerbaarheid. In dit onderzoek bleek de behoefte aan darmverteerbaar threonine voor maximale technische resultaten ongeveer 64% van de behoefte aan darmverteerbaar lysine te bedragen.
    Effect of fibrous and starchy carbohydrates in concentrates as supplements in a herbage-based diet for high-yielding dairy cows.
    Valk, H. ; Poelhuis, H.W.K. ; Wentink, H.J. - \ 1990
    Netherlands Journal of Agricultural Science 38 (1990)3B. - ISSN 0028-2928 - p. 475 - 486.
    animal husbandry - animal products - carbohydrates - chemical composition - concentrates - dairy cattle - dairy farming - dairy industry - digestibility - feed rations - feeds - ingredients - milk products - productivity - profitability - roughage
    Strukturele en niet strukturele koolhydraten in krachtvoeders van melkvee rantsoenen met silage
    Visser, H. de; Togt, P.L. van der; Tamminga, S. - \ 1990
    Lelystad : IVVO (Mededelingen IVVO no. 15) - 28
    dierhouderij - koolhydraten - melkvee - melkveehouderij - voer - productiviteit - rentabiliteit - kuilvoer - animal husbandry - carbohydrates - dairy cattle - dairy farming - feeds - productivity - profitability - silage
    Verlaging structuurwaarde in rantsoen vleesstieren
    Hanekamp, W.J.A. - \ 1990
    Lelystad : Proefstation voor de Rundveehouderij, Schapenhouderij enPaardenhouderij (Publikatie / Proefstation voor de Rundveehouderij, Schapenhouderij en Paardenhouderij 68) - 19
    maïskuilvoer - vleesvee - zetmeelverwerkende industrie - bijproducten - voer - koolhydraten - maize silage - beef cattle - starch industry - byproducts - feeds - carbohydrates
    De laatste jaren neemt op de bedrijven met vleesstieren de belangstelling voor het voeren van bijproducten uit de industriële sector sterk toe. Er zijn veel bijproducten die vaak weinig droge stof met weinig eiwit en veel energie bevatten. Ook zijn zeveelal niet structuurhoudend. De snijmaoskuil zal moeten dienen voor voldoende structuur in het rantsoen. Er is echter weinig of niets bekend over de structuurbehoefte van vleesstieren. Daarom heeft het PR op de Waiboer-hoeve onderzoek gedaan naar de hoeveelheid snijmaoskuil die door bijproducten vervangen kan worden.
    Ruminal availability of nitrogen and carbohydrates from fresh and preserved herbage in dairy cows.
    Vuuren, A.M. van; Tamminga, S. ; Ketelaar, R.S. - \ 1990
    Netherlands Journal of Agricultural Science 38 (1990). - ISSN 0028-2928 - p. 499 - 512.
    carbohydrates - dairy cattle - dairy farming - digestion - feeds - proteins - roughage - silage
    Structural and non-structural carbohydrates in concentrate supplements of silage based dairy cow rations.
    Visser, H. de; Togt, P.L. van der; Tamminga, S. - \ 1990
    Netherlands Journal of Agricultural Science 38 (1990). - ISSN 0028-2928 - p. 487 - 498.
    animal husbandry - carbohydrates - concentrates - dairy cattle - dairy farming - digestion - feed rations - feeds - productivity - profitability - roughage
    Ruminal behaviour of structural carbohydrates, non-structural carbohydrates and crude protein from concentrate ingredients in dairy cows.
    Tamminga, S. ; Vuuren, A.M. van; Koelen, C.J. van der; Ketelaar, R.S. ; Togt, P.L. van der - \ 1990
    Netherlands Journal of Agricultural Science 38 (1990). - ISSN 0028-2928 - p. 513 - 526.
    koolhydraten - concentraten - melkvee - melkveehouderij - verteerbaarheid - spijsvertering - voer - eiwitten - carbohydrates - concentrates - dairy cattle - dairy farming - digestibility - digestion - feeds - proteins
    Resultaten van een onderzoek naar afbraakeigenschappen van Neutral Detergent Fibre (NDF), zetmeel en ruw eiwit in krachtvoeringredienten
    Accelerated transformation of 1,3-dichloropropene in loamy soils.
    Smelt, J.H. ; Teunissen, W. ; Crum, S.J.H. ; Leistra, M. - \ 1989
    Netherlands Journal of Agricultural Science 37 (1989)3. - ISSN 0028-2928 - p. 173 - 183.
    boulder clay soils - carbohydrates - cellulose - chlorinated hydrocarbons - ddt - decomposition - disinfestation - loam soils - nematicides - organochlorine compounds - persistence - pesticide residues - pesticides - plant protection - soil - soil fumigation - soil sterilization
    Opslag en benutting van niet-structurele koolhydraten in de vegetatieve delen tijdens bloei en zaadvulling bij zaadgewassen : een literatuur-orientatie
    Dijk, W. van - \ 1989
    Wageningen : CABO (CABO-verslag nr. 116) - 41
    aldehyden - koolhydraten - cellulose - distributie - formatie - ketonen - voedingsstoffenreserves - zaadzetting - zaden - zetmeel - aldehydes - carbohydrates - cellulose - distribution - formation - ketones - nutrient reserves - seed set - seeds - starch
    Zetmeel in de melkveevoeding
    Cone, J.W. ; Tamminga, S. ; Togt, P. van der; Koelen, C.J. van der; Malestein, A. - \ 1989
    Lelystad etc. : IVVO (Mededelingen IVVO no. 14)
    koolhydraten - concentraten - melkvee - melkveehouderij - verteerbaarheid - voer - zetmeelwaarde - carbohydrates - concentrates - dairy cattle - dairy farming - digestibility - feeds - starch equivalent
    The plant cell wall : architecture of the plant cell wall, methods to determine cell wall fragments, cell wall degrading enzymes and their possible use in ruminants and monogastrics
    Beuvink, J.M.W. ; Mulder, M.M. - \ 1989
    Lelystad : IVVO (Rapport / IVVO no. 200) - 51
    koolhydraten - verteerbaarheid - voer - carbohydrates - digestibility - feeds
    Short-term treatment of lactating goats with recombinant bovine somatotropin and challenges with glucagon and fructose : effects on production, metabolites and hormones
    Garssen, G.J. ; Fennema, J. ; Lambooy, E. - \ 1989
    Zeist : I.V.O. (I.V.O.-report B-336) - 40
    koolhydraten - geiten - metabolisme - melkkwaliteit - melkopbrengst - somatotropine - carbohydrates - goats - metabolism - milk quality - milk yield - somatotropin
    Literatuurstudie naar de bepaling van mono- en disacchariden en polyalcoholen met behulp van instrumentale analysemethoden
    Oostrom, J.J. van; Jong, J. de; Frankhuizen, R. - \ 1989
    Wageningen : RIKILT (Rapport / RIKILT 89.55) - 20
    voedingsmiddelen - voedselproducten - landbouwproducten - voedselkwaliteit - kwaliteitscontroles - derivaten - polyethyleenglycol - glycolen - ethyleenglycol - alcoholen - thiolen - koolhydraten - aldehyden - ketonen - zetmeel - cellulose - analyse - chemie - literatuuroverzichten - analytische scheikunde - foods - food products - agricultural products - food quality - quality controls - derivatives - polyethylene glycol - glycols - ethylene glycol - alcohols - thiols - carbohydrates - aldehydes - ketones - starch - cellulose - analysis - chemistry - literature reviews - analytical chemistry
    Doel van dit onderzoek was het uitvoeren van een literatuurstudie naar de bepalingsmogelijkheden van mono- en disacchariden en polyalcoholen met behulp van instrumentele analysemethoden.
    Totaal - suikerbepaling in veevoeders : de neocuproinemethode met behulp van een segmented flow analyser
    Bosma, W.T. ; Lee, R.A. van der; Meer, J.M. van der - \ 1988
    Lelystad : I.V.V.O. (Intern rapport / Instituut voor Veevoedingsonderzoek no. 258)
    koolhydraten - voer - laboratoriummethoden - onderzoek - carbohydrates - feeds - laboratory methods - research
    Effect van olijfolie op het totaalserum- en HDL-cholesterolgehalte bij gezonde mensen.
    Mensink, R.P. ; Severijnen-Nobels, A.P. ; Vries, J.H.M. de; Katan, M.B. - \ 1988
    Voeding 49 (1988)6. - ISSN 0042-7926 - p. 138 - 142.
    koolhydraten - cholesterol - vet - vetten - voedselhygiëne - voeding - olijfolie - carbohydrates - cholesterol - fat - fats - food hygiene - nutrition - olive oil
    De resultaten van een voedingsexperiment zijn besproken. Het vervangen van verzadigde vetten door vetten met enkelvoudig onverzadigde vetzuren kan van betekenis zijn voor de preventie van hart- en vaatziekten.
    Hoe bepaal ik suikers in frites- en chipsaardappelen?
    Ludwig, J.W. - \ 1987
    Wageningen : I.B.V.L. (Publikatie / Instituut voor Bewaring en Verwerking van Landbouwprodukten 376)
    aldehyden - koolhydraten - cassave - cellulose - voedselbewaring - voedselkwaliteit - voedingsmiddelen - ketonen - aardappelen - kwaliteitscontroles - wortelgewassen als groente - zetmeel - aldehydes - carbohydrates - cassava - food preservation - food quality - foods - ketones - potatoes - quality controls - root vegetables - starch
    Degradation of low concentrations of dichlorobenzene and 1,2,4-trichlorobenzene by Pseudomonas sp. strain P51 in non-sterile soil columns.
    Meer, J.R. van der; Roelofsen, W. ; Schraa, G. ; Zehnder, A.J.B. - \ 1987
    FEMS microbiology ecology 45 (1987). - ISSN 0168-6496 - p. 333 - 341.
    benzeen - kanalen - koolhydraten - cellulose - chloride - decompositie - derivaten - hexachloorbenzeen - organische verbindingen - pseudomonas - rivieren - waterlopen - oppervlaktewater - water - benzene - canals - carbohydrates - decomposition - derivatives - hexachlorobenzene - organic compounds - rivers - streams - surface water
    Biological, chemical and physical treatment of fibrous crop residues for use as animal feed.
    Singh, K. ; Flegel, T.W. ; Schiere, J.B. - \ 1987
    New Delhi [etc.] : Indian Council of Agricultural Research [etc.] - 240
    koolhydraten - celmembranen - celwanden - cellulose - voer - rijststro - stro - strobehandeling - vezelgewassen - carbohydrates - cell membranes - cell walls - cellulose - feeds - rice straw - straw - straw treatment - fibre plants
    De mogelijkheden van een snelle test op niet - structurele koolhydraten in kleine monsters gedroogd blad- en stengelmateriaal van tomaat
    Keulen, H.A. van; Hoogendijk, J.M. - \ 1986
    Wageningen : IVT (Rapport / Instituut voor de Veredeling van Tuinbouwgewassen 230) - 13
    biologische technieken - koolhydraten - uitrusting - experimenten - solanum lycopersicum - methodologie - plantensamenstelling - tomaten - biological techniques - carbohydrates - equipment - experiments - methodology - plant composition - tomatoes
    Chromatografische analysen van de afdeling Koolhydraat- en Vetchemie
    Essers, M.L. ; Muuse, B.G. ; Kamp, H.J. van der - \ 1986
    Wageningen : RIKILT (Rapport / RIKILT 86.107) - 8
    chromatografie - koolhydraten - lipiden - chromatography - carbohydrates - lipids
    Dit rapport heeft tot doel de lezer een beeld te geven van de chromatografische analysen van de afdeling Koolhydraat- en Vetchemie. Van deze analysen zijn in het kort de toepassingen aangegeven met een verwijzing naar RIKILT-rapporten indien daarvan sprake is. Tevens zijn de analyse-omstandigheden en chromatogrammen opgenomen. Dit rapport is in het kader van GLP opgesteld en illustreert de kwaliteit van de chromatografische analysen van de afdeling.
    The in sacco degradation of curde protein and cell wall constituents in grass, alfalfa and maize silages.
    Kwakkel, R.P. ; Bruchem, J. van; Hof, G. ; Boer, H. - \ 1986
    Netherlands Journal of Agricultural Science 34 (1986). - ISSN 0028-2928 - p. 116 - 119.
    biological treatment - carbohydrates - cell membranes - cell walls - cellulose - experiments - feeds - in vitro - microbial degradation - proteins - silage
    The effect of various carbohydrate sources on the ileal and faecal digestibility of protein and amino acids in pigs
    Huisman, J. ; Hartog, L.A. den; Boer, H. ; Weerden, E.J. van; Thielen, W.J.G. - \ 1985
    In: Proceedings of the 3rd International Seminar on digestive physiology in the pig, Copenhagen 16th - 18th May 1985 = Indlaeg ved det 3. internationale seminar om fordoejelsesfysiologi hos svin, Koebenhavn 16. - 18. maj 1985 / Just, A., Foergensen, H., Fernandez, J.A., - p. 207 - 210.
    aminozuren - koolhydraten - spijsverteringsstelsel - voer - metabolisme - eiwitten - amino acids - carbohydrates - digestive system - feeds - metabolism - proteins
    The effect of various carbohydrate sources on the digestibility of minerals in the small and large intestine of pigs
    Hartog, L.A. den; Huisman, J. ; Boer, H. ; Schaijk, G.H.A. van - \ 1985
    In: Proceedings of the 3rd International Seminar on digestive physiology in the pig, Copenhagen 16th - 18th May 1985 = Indlaeg ved det 3. internationale seminar om fordoejelsesfysiologi hos svin, Koebenhavn 16. - 18. maj 1985 / Just, A., Foergensen, H., Fernandez, J.A., - p. 203 - 206.
    koolhydraten - spijsverteringsstelsel - metabolisme - carbohydrates - digestive system - metabolism
    Der reduzierende - Zuckergehalt in Kartoffeln
    Hesen, J.C. - \ 1983
    Wageningen : IBVL (Publikatie / Instituut voor Bewaring en Verwerking van Landbouwprodukten 352A) - 13
    koolhydraten - chemische analyse - chemische samenstelling - planten - aardappelen - solanum tuberosum - suikerindustrie - carbohydrates - chemical analysis - chemical composition - plants - potatoes - sugar industry
    The importance of carbohydrates for the rooting of conifer cuttings
    Lenartowicz, A. ; Ribôt, S.A. - \ 1983
    Wageningen : Centre for Agrobiological Research - 54
    wortels - stekken - koolhydraten - juniperus - chamaecyparis - vegetatieve vermeerdering - houtachtige planten als sierplanten - roots - cuttings - carbohydrates - vegetative propagation - ornamental woody plants
    Paper for the 11th ICC-congress in Vienna 1984
    Essers, M.L. ; Muuse, B.G. ; Hollman, P. - \ 1983
    Wageningen : RIKILT (Verslag / RIKILT 83.58) - 3
    diervoedering - voer - zetmeel - koolhydraten - analytische methoden - animal feeding - feeds - starch - carbohydrates - analytical methods
    In het kader van de Nederlandse normalisatie wordt door de werkgroep "Veevoeders-Koolhydraten" gewerkt aan de ontwikkeling van een methode voor de analyse van diervoeders ter bepaling van de mate van ontsluiting van het zetmeel. De methode berust op de afbraak van ontsloten zetmeel met behulp van amyloglucosidase. Voor en nadelen van de methode worden beschreven.
    Bepaling van Neutraal Detergent Fraktie m.b.v. de Fibertec System I
    Kerstens, H. - \ 1982
    Lelystad : I.V.V.O. (Intern rapport / Instituut voor Veevoedingsonderzoek no. 115) - 19
    koolhydraten - gegevens verzamelen - schatting - voer - meting - registreren - carbohydrates - data collection - estimation - feeds - measurement - recording
    Literatuuronderzoek over toepassing en analyse van polysacchariden in levensmiddelen
    Essers, M.L. ; Muuse, B.G. - \ 1982
    Wageningen : RIKILT (Verslag / RIKILT 82.32) - 18
    polysacchariden - koolhydraten - verdikkingsmiddelen - voedseladditieven - voedselanalyse - analytische methoden - polysaccharides - carbohydrates - thickeners - food additives - food analysis - analytical methods
    Doel van dit onderzoek is: Verkrijgen van inzicht in de toepassingen en de bepalingsmetboden van polysacchariden in levensmiddelen, teneinde de verschillende verdikkingsmiddelen te kunnen bepalen. Bestudeerd werden de wettelijke regelingen in Nederland, toepassingen in levensmiddelen en de analytiek van polysacchariden in levensmiddelen.
    Dietary fiber consumption in an adult Dutch population
    Staveren, W.A. van; Hautvast, J.G.A.J. ; Katan, M.B. ; Montfort, M.A.J. van; Oosten-van der Goes, H.G.C. van - \ 1982
    Journal of the American Dietetic Association 30 (1982). - ISSN 0002-8223 - p. 324 - 324.
    koolhydraten - vezel - voedsel - voedingsmiddelen - onderzoek - zetmeel - carbohydrates - fibre - food - foods - research - starch
    150 Nederlanders van 25-65 jaar uit Rhenen namen deel aan een 7-daags voedingsonderzoek om het vezelgehalte van hun voeding te onderzoeken. Dit bedroeg gemiddeld 10,5 plus of min 2,6 g per 1000 Kcal of 24,0 plus of min 6,9 g per dag. Brood en andere granen voorzagen voor 32% in de dagelijkse vezelopname, aardappelen 17%, groenten 24% en fruit 15%. De opname was significant hoger op werkdagen dan in weekends. Indeling van de proefpersonen naar de absolute vezelconsumptie, uitgedrukt in grammen per dag, en naar de vezeldichtheid van de voeding, uitgedrukt in grammen per 1000 Kcal, leverde geheel verschillende gegevens op
    Anonymous, - \ 1981
    Wageningen : Pudoc (Literatuurlijst / Centrum voor Landbouwpublikaties en Landbouwdocumentatie no. 4473)
    bibliografieën - koolhydraten - cellulose - spijsvertering - vezel - voedsel - voedingsmiddelen - darmen - dikke darm - voeding - zetmeel - voedingsvezels - bibliographies - carbohydrates - digestion - fibre - food - foods - intestines - large intestine - nutrition - starch - dietary fibres
    Ruwvezelrijk ruwvoer
    Anonymous, - \ 1981
    Wageningen : Pudoc (Literatuurlijst / Centrum voor Landbouwpublikaties en Landbouwdocumentatie no. 4529)
    bibliografieën - koolhydraten - voer - ruwvoer (roughage) - bibliographies - carbohydrates - feeds - roughage
    Ontsluiting van stro, hooi, ook met een loog of zwakzuur
    Anonymous, - \ 1981
    Wageningen : Pudoc (Literatuurlijst / Centrum voor Landbouwpublikaties en Landbouwdocumentatie no. 4536)
    bibliografieën - koolhydraten - celmembranen - celwanden - cellulose - voer - hooi - rijststro - stro - bibliographies - carbohydrates - cell membranes - cell walls - feeds - hay - rice straw - straw
    Metabole gevolgen van het gebruik van polyalcoholen en fructose - een literatuurstudie. (Deel 1 - Xylitol)
    Wiel-Wetzels, W.A.M. van der - \ 1981
    Voeding 42 (1981). - ISSN 0042-7926 - p. 309 - 320.
    koolhydraten - vezel - voedsel - voedselhygiëne - voedingsmiddelen - zetmeel - carbohydrates - fibre - food - food hygiene - foods - starch
    Suikergebruik in relatie tot tandcaries
    Anonymous, - \ 1980
    Wageningen : Pudoc (Literatuurlijst / Centrum voor Landbouwpublikaties en Landbouwdocumentatie No. 4401)
    tandcariës - koolhydraten - voedselhygiëne - bibliografieën - dental caries - carbohydrates - food hygiene - bibliographies
    Relatie tussen atherosclerose en suiker gebruik
    Anonymous, - \ 1980
    Wageningen : Pudoc (Literatuurlijst / Centrum voor Landbouwpublikaties en Landbouwdocumentatie (Puoc) no. 4398)
    arteriën - atherosclerose - bibliografieën - koolhydraten - consumptiepatronen - voedselhygiëne - voedingstoestand - arteries - atherosclerosis - bibliographies - carbohydrates - consumption patterns - food hygiene - nutritional state
    Een poging de door micro-organismen gemakkelijk ontleedbare organische stof in grond te bepalen : met bijlage : bepaling van organische koolstof in waterige (zout)oplossingen
    Bruins, E.H. - \ 1980
    Haren : Instituut voor Bodemvruchtbaarheid (Rapport / Instituut voor Bodemvruchtbaarheid no. 9-80) - 24
    koolhydraten - koolstof - cellulose - decompositie - organische stof - fysische chemie - bodem - bodemchemie - carbohydrates - carbon - cellulose - decomposition - organic matter - physical chemistry - soil - soil chemistry
    Utilization of cellulose and hemicellulose of pig faeces by Trichoderma viride
    Wit, W. de - \ 1980
    Landbouwhogeschool Wageningen. Promotor(en): E.G. Mulder. - Wageningen : Veenman - 77
    deuteromycotina - koolhydraten - cellulose - celmembranen - celwanden - stalmest - microbiologie - afvalverwerking - afvalwaterbehandeling - trichoderma viride - hemicellulosen - deuteromycotina - carbohydrates - cellulose - cell membranes - cell walls - farmyard manure - microbiology - waste treatment - waste water treatment - trichoderma viride - hemicelluloses

    The purpose of this investigation was to study the microbiological degradation of the cellulose-hemicellulose-lignin complexes of the faeces of pigs. Cellulose, hemicellulose and lignin are components of the cell wall of plants and residues of plant material occur in large quantities in faeces and other organic waste material. The development of the intensive livestock farming is leading to the production of large quantities of manure that cannot always be disposed of in the usual way by lack of agricultural land. To prevent deterioration of the environment, other ways of handling the manure should be sought. Priority should be given to those procedures according to which the insoluble organic components of the faeces are decomposed by microorganisms and the energy produced utilized by man. Examples of such procedures are the aerobic breakdown of the organic residues with production of large amounts of biomass that can be utilized as feed additive (single-cell protein). Anaerobic treatment of manure may lead to the production of methane. In the present investigation attention was centred on the aerobic break-down of the undigested organic residues of pig faeces.

    Chapter 1 contains a general introduction and gives a review of literature pertaining to waste material with cellulose, hemicellulose and lignin as main components. In the Netherlands most of the organic waste material occurs as manure, sewage sludge and domestic wastes.
    The chemistry and structure of the plant cell wall were discussed. The presence of lignin strengthens the structure of plant tissue but seriously hampers the break-down of other cell wall components like cellulose and hemicellulose which are closely linked to the lignin molecules.
    Fungi play an important part in the degradation of cellulose-hemicellulose-lignin complexes of plant residues. Some fungi are able to decompose lignin, others utilize cellulose and hemicellulose, leaving lignin untouched. Cellulolytic bacteria occur in considerable numbers in nature, but break-down of lignin by bacteria is hardly reported in the literature.
    Extra-cellular, substrate-specific enzymes produced by microorganisms are involved in the break-down of plant residues. Several enzymes play a part in the degradation of the cellulose-hemicellulose-lignin complexes. Those involved in the decomposition of cellulose are known under the collective name of cellulase. Hemicellulose is a group name for several plant cell wall heteropolysaccharides which are degraded by substrate-specific enzymes. Little is known of enzymes involved in lignin break-down.

    In Chapter 2 a survey is given of materials and methods used in this investigation. A method was described for the collection of insoluble residues of plant material from pig faeces. For practical reasons, this preparation was used in the experiments to be described.
    Chapter 3 gives the results of microscopic and chemical analyses of undigested plant residues of pig faeces. These residues were derived from plant material. mainly ground seeds and fruits, supplied as mixed feed to the animals. Various types of plant tissue (parenchyma, collenchyma and sclerenchyma) were observed showing that considerable amounts of cellulose-, hemicellulose-, and lignin-containing cell walls had passed more or less undamaged the digestive track of the pigs (Figs. 3.1 - 3.11).
    The chemical analysis of pig faeces showed that 30-40 % of the dried matter consisted of insoluble plant residues containing 65 - 70 % polysaccharides (cellulose and hemicellulose) and nearly 30 % lignin. In order to use these plant residues as carbon source for fungi, pretreatment of the material is necessary as the high lignin content hampers the ready utilization of the cellulose and hemicellulose by the cellulolytic fungi.

    Chapter 4 described the isolation of cellulolytic microorganisms. Mainly fungi were isolated and a number of them together with some fungi obtained from culture collections were tested for their ability to utilize as carbon source: (a) monosaccharides that occur in the polysaccharides of plants (b) some model polysaccharides related to plant cell walls (c) lignin and (d) undigested plant residues from pig faeces. The results of these experiments are shown in Tables 4.1, 4.2 and 4.3. None of the fungi tested was able to decompose lignin. When the undigested plant residues of pig faeces had been supplied as carbon source only 30-40 % of the material was utilized. This was mainly due to the protection of the polysaccharides against fungal attack by the lignin. In order to improve the availability of the polysaccharides to the fungi, breaking or removal of the lignin matrix of the plant tissue is required.
    Of the fungi tested for growth on residues of faeces, Penicillium nigricans, Myrothecium verrucaria and Trichoderma viride QM 9419 gave the best results. As the Trichoderma strain produced the highest amounts of cellulolytic enzymes, this organism was chosen for further research.

    In Chapter 5 experiments were described concerning the growth of Trichoderma viride on (a) crystalline cellulose (Avicel), (b) undigested plant residues from pig faeces, and (c) plant residues from faeces treated with alkali to dissolve and remove lignin. Crystalline cellulose was the best carbon source. It was almost completely utilized by T.viride giving about 250 mg of protein per g of cellulose consumed. The undigested carbon compounds of pig faeces were utilized for about 49 % and the alkali-treated residues for 60 %.
    The amount of cellulolytic enzymes in the culture liquid of T.viride, calculated per unit of soluble protein, was with cellulose as carbon source three times as high, and with alkali- treated residues twice as high as with untreated plant residues from pig faeces. Spent culture solutions of T. viride supplied with pure ,cellulose or undigested residues of pig faeces contained relatively large amounts of soluble protein. An unknown proportion of this protein represented enzymes, presumably mainly cellulolytic enzymes.
    The production of biomass from the undigested residues of pig faeces by use of Trichoderma viride ('single-cell protein') to prepare mixed feed is for the following reasons no appropriate procedure: (a) T.viride only partly utilizes the polymers of the undigested residues of pig faeces, (b) the fungal protein is mixed with part of the faeces constituents which could not be metabolized by the fungus and which are also resistant to digestion by the animal owing to the protection of cellulose and hemicellulose against break-down by the presence of lignin, (c) the soluble protein of the culture solution of the fungus is difficult to collect.

    Chapter 6. A procedure was proposed (Fig 6.1) according to which the insoluble residues of pig faeces are submitted to a solution of cellulolytic enzymes. The hydrolysis of the polysaccharides (at 50°C and pH 4.8) proceeds in a relatively short time giving a solution of sugars which can be used for further purposes. A suitable enzyme solution can be obtained by growing T.viride on residues of faeces. The enzyme solution of the spent nutrient solution of the fungus can be easily concentrated by acetone precipitation or by vacuum evaporation. The substrate for the enzymic procedure, the undigested residues of faeces, are adequately degraded when a pretreatment has been applied (grinding to a particle size of 0.08 mm).
    When the proposed procedure is applied, 150 g of insoluble residues per 1 of enzyme solution can be hydrolysed; 70 % of the residues is converted-into soluble sugars within 4 h. The cellulolytic enzymes are initially adsorbed to the insoluble substrate but are released when hydrolysis proceeds; they can be separated from the undissolved material together with the dissolved sugars. Separation of sugars and enzymes can be achieved by mixing with new substrate which adsorbs the enzymes. After separation of the sugar solution the substrate with enzymes are transferred to the reactor. In this way part of the enzymes can be re-used.
    In Chapter 6 also the results are given of the purification and separation of a number of enzymes involved in the degradation of the cellulose-, hemicellulose-, lignin complex (Fig. 6.8). The mixture of enzymes, excreted by T. viride when the organism was growing on undigested plant residues of pig faeces, was separated into several protein fractions each with its own enzyme activity with respect to different substrates, i.c. endoglucanase, exoglucanase and hemicellulase activity (Figs. 6.9-6.12).
    Degradation of undigested components of pig faeces in view of recycling of the faeces is no simple procedure. Microbial (enzymic) break-down is possible if a suitable pretreatment is applied. The economical applicability of the results obtained in this investigation will depend on: (a) the occurrence of excessive amounts of manure, (b) disposal problems, particularly in connection with the environment, (c) alternative methods for processing excessive amounts of manure.

    An investigation into the extent to which various dietary components, particularly lactose, are related to the incidence of diarrhoea in milk-fed calves
    Hof, G. - \ 1980
    Landbouwhogeschool Wageningen. Promotor(en): S. Boer Iwema, co-promotor(en): A.T. van 't Klooster. - Wageningen : Hof - 135
    voer - koolhydraten - rundvee - diergeneeskunde - spijsvertering - beroepskwalen - toxische stoffen - toxicologie - feeds - carbohydrates - cattle - veterinary science - digestion - occupational disorders - toxic substances - toxicology

    Diarrhoea is a serious disturbance of normal gut function, characterized by an excessive water excretion in faeces. The derangement is in particular observed in young, milk-fed calves. In the literature a distiction is usually made between scouring from nutritional factors and that caused by pathogenic infections. The former derangement in calves is investigated in our work.

    In practice it is well known that the new-born calf is highly susceptible to nutritional diarrhoea. Its prevention requires a number of precautions in calf nutrition and management. Nowadays these requirements also impose severe restrictions upon the type and amount of feed components suitable for use in milk replacers for these animals. Nevertheless their importance in calves, the role of diet composition and intake in this disturbance has not been systematically investigated. The lack of information prompted an investigation of the role of diet composition and intake in scouring disturbances in milk-fed calves. The work included experiments, where the main objective was to classify common diet components according to their diarrhoeic properties. The changes in the digestive processes were also measured. Associated changes in the microbial population in the lower intestine, and in electrolyte and water metabolism in body tissues were not investigated.

    The literature on the physiological changes responsible for nutritional diarrhoea in calves, reviewed in chapter 2, is rather scarce and generally refers to research in infants and man. According to these investigations proteins and carbohydrates are considered to have the greatest potential to induce scouring. Exceeding the digestive capacity of these components in the small intestine may result in either proteo-saccharolytic or saccharolytic fermentation in the hind gut. Both conditions inhibit water absorption in the colon, either because of an increased amount of components with osmotic activity in the digesta, or because of toxic properties in the end products of fermentation. Certain products of proteo-saccharolytic fermentation in particular are considered to be toxic. The derangements may lead to either putrefactive diarrhoea when dietary protein is involved, or saccharolytic diarrhoea in case of excessive carbohydrate intake. These two types of scouring are among others characterized by changes in faecal pH, being higher or lower, respectively, than in normal faeces. The literature on these effects in milk-fed calves is less clear. It provided no insight into the different diarrhoeic properties of the individual organic components, protein, fat or carbohydrates, in the diet. Another question arising was the role of abomasal clotting of the diet in scouring. This was by several authors considered to be important in putrefactive diarrhoea.

    Five experiments were carried out to investigate these aspects in young, milk-fed calves. In the first experiment (Exp. 1, section 3.3) the effect of milk composition and daily allowance on faecal characteristics (visual score, pH and DM content) was investigated in twelve subsequent periods, each lasting three days. A commercial milk replacer served as control diet in six calves, providing approximately 4.5 g protein, 3.5 g crude fat and 8 g Hex. Eq.*) lactose per kg BW per day. In the separate experimental periods either lactose, sucrose, gelatinized or raw starch, casein or fat was added in addition to that diet. The extra lactose addition to the control diet varied up to 125 % of control Hex. Eq. intake, sucrose and starch to 75 %, casein to 140 % of control crude protein intake and fat to 60 % of control crude fat intake. In one period the daily offer of the control diet was increased to 175 % of the normal intake.

    The carbohydrate additions resulted in a rapid fall of faecal consistency and pH (table 2). Sucrose and the starches proved to be more critical in this respect than lactose, although the response to starch was slightly delayed. Dietary lactose induced quickly fermentative scouring when fed in excess of 10 g Hex. Eq. per kg BW per day. Calf`s response to lactose was not affected by animal's age in this experiment, contrary to that reported by several authors. High concentrations of well homogenized fats of high nutritional quality seemed to become critical too, although the effect was less pronounced than with similar increases of carbohydrates (table 3). Scouring was also observed on high milk intakes (table 4). The response of faecal pH and DM content in this period suggested an interaction in scouring effects between the dietary components. The experiment did not allow any conclusion to be drawn as to whether or not the interaction interfered with the digestion or the microbial fermentation of the undigested dietary residues in the lower intestine. Casein did not affect faecal characteristics, irrespective of the level of intake.

    Although faecal responses to the individual treatments were evident, they were less informative about the quantitative differences in diarrhoeic properties of the individual components tested. Faecal pH was usually closely related to visual score when increasing carbohydrate intake. This parameter, however, gave less information on the effect of high fat or protein intake. A diagnosis based on DM content alone might lead to misinterpretation of the severity of scours, as was demonstrated in the starch treatments. This criterion does not always reflect the increased water excretion in diarrhoeic faeces. It may be affected simultaneously by a higher excretion of components exerting no osmotic effects, e.g. mucous substances.

    The absence of scouring in the high casein treatments seemed to conflict with the results cited in the literature. These postulate the risk of putrefactive scouring induced by dietary protein, in particular, when milk clotting in the abomasum is insufficient. The role of abomasal clotting in diarrhoea was therefore investigated in Exp. 2 (section 3.4). For that purpose a liquid commercial milk replacer was directly infused into the proximal duodenum, replacing quantitatively the digesta collected at that site. The effect of this treatment on faecal characteristics, visual score and pH, was measured in two experimental periods lasting 4 x 12 h and 4 x 24 h, respectively.

    The milk infusate increased substantially the firmness of the faeces, especially in the latter period (table 5). Faeces became so firm that the animals had obviously problems in defaecating. This unexpected, and yet still unexplainable, result clearly shows that no negative relation exists between abomasal clotting of milk protein and scouring.

    The importance of undigested dietary components in the large intestine digesta in the scouring derangement was more closely investigated in Exp. 3, 4 and 5 with fifteen ileal fistulated calves (section 3.5). The higher inflow of dietary components into the colon was simulated by an infusion of graded levels casein, fat or lactose into the distal end of the ileum. Casein was infused at 5 and 10 % of oral crude protein intake. The fat infusion was 5 % of crude fat intake and those of lactose 5, 10 and 20 % of oral NFE intake in the control milk replacer. Faecal response (visual score, pH and DM content) was measured, as well as the ileal and faecal apparent digestibility.

    The effect of the infusates on faecal characteristics (table 6) merely confirmed those observed in Exp. 1, although faecal responses were rather mild. The casein and fat treatments did not change faecal characteristics. Only the highest level of lactose infusion, 20 % of oral NFE intake, affected all faecal parameters. The control diet was highly digestible in these experiments (table 7). The digestion and absorption of most dietary components was almost completed at the distal end of the small intestine. Only a minor part of N and NFE disappeared in the lower intestine together with a substantial amount of Na. Faecal digestibility was hardly affected by the casein and fat infusates (table 8). N and NFE excretion in the faeces increased, however, when the lactose infusion exceeded 5 % of oral NFE intake. Faecal N excretion increased by 15-16 ing per g lactose infused in addition to the 5 % treatment.

    The results of Exp. 1-5 indicate that high intakes of milk protein of standard quality, i.e. casein, are not detrimental to young calves. High intake of fats or carbohydrates may result in nutritional scouring. The fat concentration of the diet is, however, presumably more limited by technological capabilities than by the level tolerated by these animals. It was therefore decided to undertake further work on the effect of carbohydrates. As lactose is the most important carbohydrate in milk replacers, this sugar received our main attention.

    The literature on the digestion and absorption of carbohydrates (chapter 4) indicates that milk-fed calves have an impressive ability to digest lactose and to absorb glucose and galactose. Consequently their levels of intake permitted in these animals are rather high. The enzymatic activity for digestion of other carbohydrates is much less well developed or even absent. Their intake is therefore strictly limited or even not tolerated at all. The literature is less informative about the digestive changes in young calves responsible for the nutritionally induced scouring. Neither have the consequences of the derangement for animals' health been investigated systematically. Four important questions in this respect needed further clarification. They concerned: (1) the maximal limit of lactose permitted in milk replacers for young calves, (2) the effect of excessive lactose intake on the digestion and absorption in the small intestine, (3) the significance of the quantitative and qualitative characteristics of ileal digesta in scouring and (4) the effect of fermentative diarrhoea on the water and mineral excretion. These aspects were investigated in ten experiments (Exp. 6-15, Chpt. 5).

    Exp. 6 and 7 were designed to investigate the relationship between lactose intake, carbohydrate digestion and absorption, using jugular vein blood sugar as a parameter, and scouring in young calves. In the former experiment graded levels of dietary lactose were fed to thirty calves, allotted to five groups of six animals. The individual faecal responses were measured and related to the individual blood sugar responses. Lactose was offered in three treatments, A, B and C, supplying 10, 13.5 and 17 g Hex. Eq. per kg BW per day, respectively. All treatments were fed for three successive days in each period. In Exp. 7 treatment A and C were offered to nine calves. The experimental periods were prolonged in this trial from three to seven days in order to test the possible effect of adaptation to high lactose intakes.

    The results in both experiments confirm that fermentative scouring quickly occurs, when the daily lactose intake exceeds 10 g Hex. Eq. per kg BW in calves aged at least four weeks. The response in blood sugar level provided evidence that the digestion and absorption of lactose increase with the daily intake. Treatment C resulted in significantly higher blood sugar levels than treatment B; those were in both treatments significantly higher than in control treatment A (table 14, 16). The blood sugar responses seemed also to indicate that calves, responding in a less pronounced way regarding the blood sugar curve in treatments B and C, suffer scouring more seriously. No adaptive response in the blood sugar curve occurred when the high lactose treatment was prolonged to seven days. However, calves adapt quickly to high lactose intake in their first four weeks of life. No effect of age was demonstrated from 4-12 weeks of age on the limit of lactose tolerance. The slope of the blood sugar curve, however, becomes steeper as animals grow older.

    The effect of dietary lactose on the digestive processes in the small intestine was further investigated in six experiments. Digesta flow rate*), transit time*) and digesta osmolality were the main parameters investigated in Exp. 9, 10 and 11 (section 5.4. 1). In Exp. 9 sixteen calves were used for this purpose, either fitted with re-entrant duodenal or ileal cannulae, or not fistulated. The effect of dietary lactose was tested in treatments A and C, offering 10 and 17 g Hex. Eq. lactose per kg BW per day, respectively. The duodenal or ileal flow rates of wet digesta, N and reducing substances were measured in the fistulated calves. The non-fistulated animals served as a 'control group' to test the scouring effect of the dietary treatments in this experiment. The flow rates of ileal wet digesta, measured in Exp. 10, 11 and 13, closely agreed with those observed in Exp. 9. In these trials treatment A and C were tested and also treatment D, offering 8 g Hex. Eq. lactose and 3 g Hex. Eq. sucrose per kg BW per day.

    The scour-inducing level of lactose (treatment Q neither affects abomasal transit time or duodenal flow rates of wet digesta, nor that of its components, N and reducing substances (table 19). Neither the digesta transit time, nor N flow rates are different at the end of the ileum for either treatment (table 29). The flow rates of wet digesta and reducing substances are, however, substantially higher when daily lactose intake increases from ca. 9- 10 to ca. 16-17 g Hex. Eq. per kg BW. Treatment D, supplying sucrose, basically acts in scouring in a similar way as lactose, although the calves respond more seriously to this treatment (table 21). Compared with the lactose diets, wet digesta flow rates into the lower intestine are significantly enhanced and digesta transit time in the abomasurn plus small intestine is reduced in the sucrose treatment.

    The effect of high lactose intake on the apparent digestibility of dietary components in the small intestine was measured in Exp. 12 (section 5.4.2) On account of the interaction observed in Exp. 1 the experiment was designed to investigate also the influence of diet composition on the digestion. Fifteen calves, fitted with re-entrant ileal cannulae, were allotted to three groups, receiving either diet A, B or C in five experimental periods of five days each. In P 1 and P 5 the apparent digestibility of the diets, offered in amounts equal to those usually given in treatments A, B and C, was investigated. In the other periods the animals received equal amounts of lactose with the three diets; 15.3, 12.2 and 9 g Hex. Eq. per kg BW per day in P 2 , P 3 and P 4 , respectively.

    The feed intake and digestive ability of the calves declined when the experiment lasted longer. This prevented an accurate determination of the apparent digestibility. Covariance analyses provided much evidence that the apparent digestibility coefficients of the main dietary components in the small intestine are hardly affected by lactose intake. Only the carbohydrate fraction is relatively less efficiently digested when lactose intake increases (table 22). It also seems to reduce the apparent digestibility of crude protein. It confirmed our view that, although the lactose digestion and absorption improves in the high lactose treatments, the improvement is insufficient to prevent greater amounts of carbohydrates flowing into the hind gut. The apparent digestibility in the small intestine is not substantially affected by diet composition. The differences in Exp. 12 were too small to be responsible for the large effect of diet composition on faecal characteristics on high milk intake in Exp. 1. These latter differences were obviously caused by differences in microbial fermentation in the lower intestine. The level of lactose that can be tolerated is obviously an absolute amount depending upon body weight, not on the percentage composition of the diet.

    In two subsequent trials, Exp. 13 and 14, the significance of lactase activity in the maximal limit of lactose intake was investigated (section 5.4.3). The previous experiments give little information on that aspect, especially because of a discrepancy between the results obtained in analysis of reducing substances and of the individual sugars, glucose, galactose and lactose, according to a standard enzymatic method. Exp. 13 was designed to get more information on that point and to determine more accurately the individual sugar content in ileal digesta. For that purpose diets A and C were fed to five calves, fitted with re-entrant ileal cannulae. Ileal digesta and faeces were quantitatively collected in separate experimental periods.

    The results (table 24, 25 and 26) suggest that glucose is efficiently absorbed, mainly in the small intestine. In agreement with the literature, absorption of galactose is reduced in that region, in particular when lactose intake increases. Lactose recovery in ileal digesta and faeces is low compared with galactose recovery. The analyses on carbohydrate composition strongly suggested that the major part of galactose in ileal digesta was a component of other oligosaccharides, containing approximately 4.5 to 4.6 times as much galactose as glucose molecules. These compounds would explain the observed discrepancies between reducing substances and the individual sugars analysed, and also the lower efficiency of P- galactosidase in the 'lactose' digestion in ileal and faecal samples. The fact that these compounds were not found in the milk diet or duodenal digesta strongly suggested that they were synthesized in the small intestine during lactose digestion.

    Whether or not lactose is converted by lactase into oligosaccharides in calves, was furher investigated in Exp. 14. In this trial the high lactose diet C and a high hexose diet C' were fed. Both diets offered daily equal amounts of Hex. Eq.; 16 to 17 g per kg BW. The diets were fed to ten calves, fitted with re-entrant ileal cannulae and to eight non-fistulated calves. Ileal digesta and faeces of the fistulated animals were quantitatively collected and analysed by gas chromatography for sugar content. The non-fistulated calves served as a 'control group ' to measure the scouring response of the dietary treatments more accurately.

    Both diets induced scours in the calves (table 27). Treatment C' seemed to be slightly more conducive to diarrhoea and resulted in a weak condition of the calves, probably resulting from lesions in the intestinal mucosa. These adverse effects still carried over when this treatment had been stopped for three weeks and replaced by control diet A. The difference between both treatments was also reflected in the flow rates of ileal wet digesta, being higher in treatment C' than in the lactose treatment C (table 28).

    The sugar analyses in ileal digesta, collected in treatment C, proved that substantial amounts of hexoses were bound as oligosaccharides, i.e. lactose, maltose and other di- and trisaccharides, mainly consisting of galactose molecules. The samples collected in treatment C' contained more free and total glucose and galactose, but hardly any oligosaccharides. The recovery of total glucose and galactose in both treatments confirms the preferential absorption of hydrolysed hexoses over free hexoses in the intestinal lumen.

    Free glucose and galactose were the main sugars excreted in the faeces (table 29). Traces of lactose and other disaccharides were only found in faeces collected in treatment C, but not in treatment C'. Trisaccharides were not excreted in the faeces. The recovery of total glucose and galactose in the faeces, although almost negligible in both treatments, was slightly higher when lactose was fed.

    The results in Exp. 13 and 14 confirm the conversion of lactose into other oligosaccharides by lactase in the small intestine of calves. These compounds are not responsible for the lower galactose absorption in relation to glucose absorption. The apparent digestibility of galactose in the small intestine is slightly higher when lactose is fed instead of the individual hexoses, glucose and galactose. They also confirm that the limits put on galactose absorption are mainly responsible for maximal lactose digestion and absorption. Although some lactose is recovered at the end of the small intestine, this quantity is much lower than the total galactose recovery. Moreover, the lactose in ileal digesta may to some extent originate from transgalactosylation. The total galactose content is the main factor responsible for the changes in ileal digesta, when diets high in lactose are given to young calves.

    The effect of the quantitative and qualitative characteristics of ileal digesta in scouring was investigated in two trials (Exp. 8 and 11). In the latter experiment ileal digesta were quantitatively collected in calves, receiving the sucrose treatment D, and infused into the distal ileal cannula of calves, receiving control diet A, and vice versa. The three calves showed severe scouring when infused with ileal digesta from diet D (table 30). The other three calves, receiving the diet A infusate, responded with normal faecal characteristics despite the sucrose intake. The results confirmed that the changes in ileal digesta, when feeding an excess of carbohydrates, are responsible for the scouring phenomenon.

    The carbohydrate content in ileal digesta is generally presumed to be the main factor in scouring. However, the response of calves to carbohydrate infusions at that site were rather mild in Exp. 5 in relation to those usually observed in treatment C. It prompted us to repeat that trial, infusing lactose and galactose in amounts equal to 40 % of oral Hex. Eq. intake (Exp. 8). All sugars were infused as an aqueous solution, isotonic with ileal digesta (312 m osmol per L). An isotonic NaCl solution served as a control treatment in this experiment.

    The introduction of carbohydrates into the colonic lumen quickly reduced faecal consistency, pH and DM content (table 31).The responses were almost similar to those in calves severely suffering scours on high dietary lactoseintakes and indicate that the carbohydrates in ileal digesta are those primarily responsible for the scouring.

    The effect of lactose induced scouring on the water excretion of the calves was investigated in Exp. 9, 14 and 15, measuring quantitatively the urine and the water excretion in faeces in treatments A, B and C (section 5.6). The results suggest that lactose induced scouring in milk-fed calves does not necessarily change the total water excretion (table 32). The extra faecal water loss is compensated for by a lower urine excretion. The carbohydrate excretion in the urine is, however, significantly increased in high dietary lactose intake (table 33).

    The effect of dietary milk sugar in diets A, B and C on the absorption and excretion of macro minerals in milk-fed calves was investigated in Exp. 15. These diets were fed in three successive periods of five days each to twenty calves, ten of them fitted with re-entrant ileal cannulae. The absorption of Na, K, Cl, Ca, P and Mg in the small intestine was investigated in the fistulated calves. The nonfistulated animals served to measure the faecal apparent absorption and the retention of these minerals.

    The apparent absorption of the minerals in the small intestine in treatment A was rather high (table 34). The results in that treatment agree with those cited in the literature. The absorption of most elements is almost completed in the small intestine, except of Na, which is absorbed in considerable amounts in the large intestine. The absorption in the small intestine of K, Cl, Ca and in particular of Na decreases when dietary lactose intake increases. This effect is also reflected in the apparent faecal absorption and in the retention of these minerals, but only the changes in the absorption and retention of Na and K were significant in this experiment (table 35). Most animals did not suffer net electrolyte losses in treatment B or C. However, that did occur with Na in some individual calves, that responded severely to the lactose treatments (table 36).

    The results obtained in these fifteen experiments prove that lactose is the only carbohydrate tolerated in considerable amounts in milk replacer diets by young calves. The maximal limit of lactose, ca. 10 g Hex. Eq. per kg BW per day, seems to be slightly higher than that of glucose and galactose. It is not yet clear, whether or not the oligosaccharides in the ileal digesta, originating from the conversion during lactose digestion, may have some benefits in this respect. When, however, the lactose intake exceeds the limit of hexose, and in particular that of galactose absorption, scouring occurs. Related changes in intestinal digesta and faecal characteristics are basically similar as those observed in infants and man, suffering hypolactasia.

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