Staff Publications

Staff Publications

  • external user (warningwarning)
  • Log in as
  • language uk
  • About

    '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.

    We have a manual that explains all the features 

    Current refinement(s):

    Records 1 - 20 / 60

    • help
    • print

      Print search results

    • export

      Export search results

    Check title to add to marked list
    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.
    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.

    Biorefinery of leafy biomass using green tea residue as a model material
    Zhang, C. - \ 2016
    Wageningen University. Promotor(en): Johan Sanders, co-promotor(en): Marieke Bruins. - Wageningen : Wageningen University - ISBN 9789462576902 - 156
    biorefinery - biomass conversion - leaves - biomass - green tea - tea - alkaline pulping - pectins - lignocellulose - environmental impact - processes - plant protein - food - biobased economy - bioraffinage - biomassaconversie - bladeren - biomassa - groene thee - thee - alkalische pulpbereiding - pectinen - lignocellulose - milieueffect - processen - plantaardig eiwit - voedsel - biobased economy

    Summary

    With the rapidly growing world population and improving living standards, food demand is increased with a simultaneous desire for less human impact on the environment, such that “Twice the food production at half the ecological footprint” could be the EU goal for 2050. In fact, a boost in food demand is mainly required in developing countries, where the farmlands are limited and/or they are of poor quality. Rather than improving crop-production yield, developing biorefinery technology with unused biomass, such as leaves, in developing countries may be the key to fulfil the food demand.

    Four major components, protein, pectin, lignin, and (hemi-) cellulose, account for more than 70% of the materials in leaves in almost all species. Among these components, protein and pectin can be used in food and animal feed, and they are key components for supplementing food production. However, the production and application of leaf products is limited for four reasons: unstable raw materials, complex components, rigid plant cell walls, and underdeveloped leaf logistics and economics. The limitations cause low pectin and protein yields, and low cost-efficiency in current extraction technologies, including mechanical milling, chemical extraction (acid and alkaline), solvent extraction, and ammonia protein extraction. Development of an integrated process for multiple products might be a good option for leaf biorefinery, but the compatibilities of these processes were unknown.

    The aim of this study was to develop new processes and applications that optimally utilize all components, particularly protein, of leafy biomass in the feed and/or food industry using green tea residues as a starting material. The method should also be applicable to other leafy biomass. The research started from the development of alkaline protein extraction technology as presented in Chapter 2. We found that in alkaline protein extraction, temperature, NaOH amount, and extraction time are the parameters determining protein yield, while pH and volume of extraction liquid are critical parameters for production cost. After optimization, more than 90% of leaf protein could be extracted at a cost of 102€/ton protein by single step alkaline extraction. The extracted protein nutritional value was comparable to soybean meal and this technique can be adapted to various leafy biomass. Main drawback of this technique is the overuse of alkali, generation of salts, and the destruction of key amino acids, such as lysine, during the extraction. We tried to overcome its drawbacks by developing integrated process with a recycle for chemicals.

    Chapter 3, 4, 5, and 6 refer to the integrated biorefinery. For a better design, we investigated how the alkali aided protein extraction (Chapter 3), and proved that alkaline protein extraction was not facilitated by increased solubility or hydrolysis of protein, but positively correlated to leaf tissue disruption. HG pectin, RGII pectin, polyphenols, and organic acids can be extracted before protein. Protein extraction can then be followed by the extraction of cellulose and hemi-cellulose. RGI pectin and lignin yield were both linearly correlated to protein yield, which indicated that they are likely to be the key limitation to leaf protein extraction. Based on the above findings, an integrated biorefinery that combined protein extraction with a pre-treatment was proposed. In Chapter 4, ethanol, viscozyme, and H2O2 were selected for pre-treatments targeting on the removal of polyphenols and pigments, carbohydrates, and lignin accordingly. Ethanol and viscozyme could extract their targeting components efficiently while H2O2 could bleach GTR with no lignin extracted. The best pre-treatment was the combination of viscozyme and 50% ethanol extraction, which not only reduced the use of alkali by 50%, but also improved protein content and its nutritional value. As pectin can be applied for food or chemicals, enzyme and PBS buffer were investigated for pectin extraction (Chapter 5). Both enzyme and PBS buffer extraction could not only extract high yield HG pectin (predominated by galacturonic acid) with no protein extraction, but also reduced alkali usage in subsequent protein extraction. Pectin obtained using PBS buffer could be present in its native form, which can be precipitated by 40% ethanol. Buffer is suggested to extract pectins when pectins are to be used in food. Otherwise, hydrolyzed pectin that mainly contains galacturonic acid, can be converted to other useful chemicals. For this the enzymatic methods, such as using Viscozyme® L, are recommended.

    Alkali usage was further optimized. It was found that by using potassium hydroxide, the protein extraction efficiency was similar to that using sodium hydroxide. The waste water, mainly containing potassium salts, can then be used as fertilizer. This technique is highly depending on the location of factories, which should be built close to the field. Alternatively, calcium hydroxide can be used. As calcium salts can be precipitated by CO2 and calcium hydroxide can be regenerated through burning of the precipitate, this scheme is sustainable and adaptable to most situations. However, as calcium also precipitated pectin, ployphenols, and even proteins, the protein yield is relatively low. Although a pre-treatment can improve extraction efficiency of calcium hydroxide, economic results suggested that a pre-treatment is not necessary unless the products obtained by pre-treatment have an attractive market value.

    In Chapter 7, we extend our knowledge on leaf biorefinery with some additional experiments and literature. Simplified models of leaf tissues and cell walls were proposed and used to explain the mechanism of alkaline protein extraction. The models were also used to explain other mechanisms for protein extraction; mechanical milling, steam explosion, acid, and enzyme aided extraction. The possible improvements of leaf biorefinery economics were illustrated either by reducing production cost, by e.g. using counter current extraction or ultrafiltration, or by upgrading product value by applying protein and pectin in food. The processes recommended in this thesis show an excellent prospective, in which they are applicable to other leaf biomass and suitable for small-scale production.

    Targeted and non-targeted effects in cell wall polysaccharides from transgenetically modified potato tubers
    Huang, J.H. - \ 2016
    Wageningen University. Promotor(en): Harry Gruppen; Henk Schols. - Wageningen : Wageningen University - ISBN 9789462576292 - 126
    potatoes - cell walls - polysaccharides - transgenic plants - pectins - tubers - xyloglucans - genetically engineered foods - galactans - characteristics - nontarget effects - effects - aardappelen - celwanden - polysacchariden - transgene planten - pectinen - knollen - xyloglucanen - genetisch gemanipuleerde voedingsmiddelen - galactanen - karakteristieken - onbedoelde effecten - effecten

    The plant cell wall is a chemically complex network composed mainly of polysaccharides. Cell wall polysaccharides surround and protect plant cells and are responsible for the stability and rigidity of plant tissue. Pectin is a major component of primary cell wall and the middle lamella of plants. However, pectin biosynthesis in planta and the mechanisms underlying the influence of structural differences arising from a modified biosynthesis machinery on functional properties remain poorly understood. In our research, the changes in the chemical structures of cell wall polysaccharides after transgenic modification of potato tuber polysaccharides were examined. The cell wall material from potato wild-type varieties, from known and from new potato transgenic lines targeting changes of the homogalacturonan or rhamnogalacturonan I backbone were isolated and characterized. The modified cell wall polysaccharides were examined by determining their individual monosaccharide levels on fresh weight base and their cell wall characteristic parameters, and levels of acetylation and methyl esterification of cell wall pectin. Data for both targeted and non-targeted structures of cell wall polysaccharides from wild-type and transgenic potatoes were obtained. A shorter galactan side chain was found from the buffer soluble pectin and calcium bound pectin of β-galactosidase (β-Gal) transgenic lines. All pectin fractions from rhamnogalacturonan lyase (RGL) transgenic lines had less galactan chains attached to their rhamnogalacturonan I backbones. Two uridine diphosphate-glucose 4-epimerase (UGE) transgenic lines, UGE 45 and UGE 51, had diverse effects on length of the galactan side chain. The xyloglucans from the RGL and UGE transgenic lines retained its XXGG building blocks but differed in the proportion of repeating units compared to the respective wild-type varieties. In contrast, the β-Gal transgenic lines predominantly consisted of XXXG-type xyloglucan in the 4 M alkali extract, but showed XXGG-type building blocks in 1 M alkali extract. In addition, a quick-screening method was validated and used to analyze 31 transgenic lines and their respective wild-type potato varieties. An overall comparison of pectin backbone, pectin side chains, acetylation and methyl-esterification of pectin, pectin content and (hemi)cellulose content of cell wall polysaccharides from these transgenic lines provided a better insight in the frequency, level and combination of both targeted and non-targeted structural changes compared to that of their respective wild-type varieties. The same evaluation method was used to correlate cell wall composition in wild-type and selected transgenic lines and their established gene expression with the texture of corresponding cooked potato cubes. Changed physical properties for the genetically modified tubers could be connected to specific cell wall characteristics. Tubers from transgenic lines containing cell wall pectin with short galactan side chains were less firm after cold processing compared to wild-type tubers. The enhanced understanding of transgenic modifications of potato tubers resulting into significant targeted and non-targeted modifications in cell wall polysaccharides will lead to a better selection of potato lines with tailored cell wall characteristics and desired properties of the tubers during processing.

    Potato cell walls are composed of pectin, hemicellulose and cellulose. Cell wall polysaccharides are responsible for the stability, rigidity and flexibility of plant tissue. Pectin, a major component of primary plant cell walls, primarily consists of homogalacturonan (HG) and rhamnogalacturonan I (RG-I). To understand the structure–function relationships of potato cell wall pectin, this study aimed to identify the characteristics of both pectin and other polysaccharides as present in cell wall material (CWM) and of individual polysaccharide populations from wild-type potato varieties and their respective transgenic potato lines.

    Chapter 1 gives a general introduction to the fine chemical structures of potato cell wall polysaccharides, the main models of cell wall architecture and the cell wall-degrading enzymes, which include pectinases, hemicellulases and cellulases. In addition, transgenic modification of the cell wall through the heterologous expression of various enzymes from fungal or plant origin that could modify potato cell wall polysaccharides in planta is addressed. Transgenic modifications of potato cell wall polysaccharides that targeted pectin structures and cellulose levels are summarised. However, due to unsuccessful starch removal during CWM isolation and incomplete analysis of CWM yield and composition, characteristics regarding the different cell wall polysaccharides from previously-studied transgenic potato lines are hardly available.

    CWMs were extracted from the Karnico (wild-type) potato and its transgenic lines that expressed either β-galactosidase or rhamnogalacturonan lyase (Chapter 2). Improved starch removal procedures proved to be successful. Pectic polysaccharides were fractionated from CWMs of wild-type potato and its transgenic lines β-Gal-14 and RGL-18. Most β-Gal-14 pectin populations had less galactose (Gal) than wild-type, indicating that the transgenic line had shorter galactan side chains, although the side chain length differed for individual pectin populations. The ratio of HG:RG-I was introduced to evaluate the pectin backbone structure. High HG:RG-I ratios were consistently found in RGL-18 pectic polysaccharide populations. A low level of RG-I segments in combination with lower Gal contents indicated the removal of the galactan-rich RG-I segments in all pectin populations of RGL transgenic lines. In addition, RGL-18 transgenic modification increased the methyl-esterification and lowered the acetylation of pectins present in hot buffer extracts, when compared to wild-type. No effect on pectin esterification was found for β-Gal transgenic lines. Side effects of the mutation generated unexpected changes in the various pectin populations.

    The xyloglucan structure was extensively modified after transgenic modification of the pectin structure. Two xyloglucan extracts were obtained from the Karnico and its β-Gal-14 and RGL-18 transgenic lines (Chapter 3). The extracts of the Karnico and RGL-18 lines were mainly comprised of the XXGG-type xyloglucan as represented by XXGG and XSGG as predominant repeating units. In contrast, the XXXG-type xyloglucan was primarily present in the β-Gal-14 4 M alkali extract built up by LLUG repeats, although XXGG type of xyloglucan was present in the 1M alkali extract. Both the RGL and β-Gal transgenic lines had different proportions of xyloglucan building blocks (XSGG/XXGG ratios) than wild-type. After transgenic modification of pectin backbone or pectin side chains, the xyloglucan structures has been biosynthetically modified by plant itself.

    Uridine diphosphate (UDP)-glucose 4-epimerase (UGE) catalyses the conversion of UDP-glucose into UDP-galactose, which hypothetically should lead to more galactose being built into the cell wall polysaccharides. CWMs from the Kardal (wild-type) potato and its UGE45-1 and UGE51-16 transgenic lines were isolated, fractionated and characterised (Chapter 4). Both the UGE45 and UGE51 genes encoded for UGE enzymes, but the corresponding transgenic lines exhibited different modifications of the galactan side chains and of other cell wall structures. The Gal content of CWM from the UGE45-1 transgenic line was 38% higher than that of the wild-type and resulted in longer pectin side chains. The Gal content present in CWM from UGE51-16 was 17% lower than that of wild-type, which resulted in a slightly shorter galactan side chains for most pectin populations. Both UGE transgenic lines showed a decreased acetylation and an increased methyl-esterification of the cell wall pectin. Side effects were found in the xyloglucan structures of the transgenes as reflected by different proportions of XSGG/XXGG repeating units in comparison to wild-type. Pectin side chain biosynthesis had not only a varying level of galactan side chain modification, but also influenced the structure and possibly the interaction of other cell wall polysaccharides.

    In Chapter 5, a new screening strategy is introduced to evaluate higher numbers of transgenic potato tubers via CWM yield and sugar composition. A total of four wild-type potato varieties and 31 transgenic lines were evaluated to determine the effects on targeted structures including RG-I or HG pectin backbone elements, galactan or arabinogalactan side chains, acetyl groups of pectin and cellulose levels. Modification of the pectin backbone or pectin side chains in the transgenic lines has either a simultaneous increase or simultaneous decrease of HG:RG-I ratio, side chain length and methyl-esterification of pectin. The pectin esterification transgenic line exhibited only limited side effects. The cellulose level targeted lines had also high HG:RG-I ratios, longer galactan chains and similar pectin content compared to the wild-type, indicative for a less branched pectin backbone with longer side chains. From the monosaccharide composition data, various pectin and cell wall characteristics parameters are suggested as powerful indicators of cell wall polysaccharide structure.

    In Chapter 6, the achievements of this research are summarised and discussed in the context of potato cell wall architecture. The strategy and outcome of a quick screening method for multiple transgenic lines and an in-depth analysis of individual pectin and xyloglucan populations for the evaluation of potato CWMs is discussed. Furthermore, the texture of steam-cooked potatoes and the stability of potato cubes after freeze-thaw cycles are correlated with gene expression and cell wall composition in wild-type and selected transgenetically modified potato tubers. CWMs from transgenetically modified potatoes showed different physical properties during processing. In isolated CWMs, acetylation of cell wall pectin, molar Gal levels and starch content were the main parameters that could be related to the texture or firmness of tubers. Tubers from transgenic lines that resulted in shorter pectin side chains felt apart more easily after several freeze-thaw cycles than wild-type tubers and tubers with an increased length of pectin side chains. The modification of both targeted as well as non-targeted structures have now been shown to occur in many different potato transgenic lines, but precise mechanisms and consequences for the cell wall architecture remain unclear. Research performed so far, as well as research needed for getting a better understanding of plant cell wall architecture, is discussed.

    Characterisation of cell-wall polysaccharides from mandarin segment membranes
    Coll-Almela, L. ; Saura-Lopez, D. ; Laencina-Sanchez, J. ; Schols, H.A. ; Voragen, A.G.J. ; Ros-García, J.M. - \ 2015
    Food Chemistry 175 (2015). - ISSN 0308-8146 - p. 36 - 42.
    hairy ramified regions - cross-flow filtration - pectolytic enzyme - citrus-fruit - pectins - degradation - extraction - skin - rhamnogalacturonase - populations
    In an attempt to develop a process of enzymatic peeling of mandarin segments suitable for use on an industrial scale, the cell wall fraction of the segment membrane of Satsuma mandarin fruits was extracted to obtain a chelating agent-soluble pectin fraction (ChSS), a dilute sodium hydroxide-soluble pectin fraction (DASS), a 1 M sodium hydroxide-soluble hemicellulose fraction (1MASS), a 4 M sodium hydroxide-soluble hemicellulose fraction (4MASS) and a cellulose-rich residue (3.1, 0.9, 0.4, 0.7 and 1.6% w/w of fresh membrane, respectively). The ChSS pectin consisted mainly of galacturonic acid followed by arabinose and galactose. The DASS fraction contained less galacturonic acid and more neutral sugars than ChSS. Eighty-nine percent of the galacturonic acid present in the segment membranes was recovered in the above two pectin fractions. The two hemicellulosic fractions consisted of two different molecular weight populations, which also differed in their sugar composition. Arabinose, xylose, mannose, galactose and glucose were the main sugar constituents of these hemicellulose fractions. In addition to an (arabino)xylan and a xyloglucan, the presence of an arabinogalactan is suggested by the sugar composition of both hemicelluloses. The pectin fractions were also characterised by their degradability by the pectic enzymes polygalacturonase, pectinmethylesterase and rhamnogalacturonan hydrolase. However the degree of degradation of the pectin fractions by enzymes differed, and the amount of the polymeric materials resistant to further degradation and the oligomeric products also differed. Using pectic enzymes it is possible to obtain peeled mandarin segments ready to eat or for canning.
    How Does Alkali Aid Protein Extraction in Green Tea Leaf Residue: A Basis for Integrated Biorefinery of Leaves
    Zhang, C. ; Sanders, J.P.M. ; Xiao, T.T. ; Bruins, M.E. - \ 2015
    PLoS ONE 10 (2015)7. - ISSN 1932-6203
    functional-properties - antioxidant activity - sugar-beet - cell-walls - cellulose - pectins - biomass - acid - degradation - hydrolysis
    Leaf protein can be obtained cost-efficiently by alkaline extraction, but overuse of chemicals and low quality of (denatured) protein limits its application. The research objective was to investigate how alkali aids protein extraction of green tea leaf residue, and use these results for further improvements in alkaline protein biorefinery. Protein extraction yield was studied for correlation to morphology of leaf tissue structure, protein solubility and hydrolysis degree, and yields of non-protein components obtained at various conditions. Alkaline protein extraction was not facilitated by increased solubility or hydrolysis of protein, but positively correlated to leaf tissue disruption. HG pectin, RGII pectin, and organic acids were extracted before protein extraction, which was followed by the extraction of cellulose and hemi-cellulose. RGI pectin and lignin were both linear to protein yield. The yields of these two components were 80% and 25% respectively when 95% protein was extracted, which indicated that RGI pectin is more likely to be the key limitation to leaf protein extraction. An integrated biorefinery was designed based on these results. Introduction
    Enzymatic fingerprinting and modification of acetylated pectins
    Remoroza, C.A. - \ 2014
    Wageningen University. Promotor(en): Harry Gruppen; Henk Schols. - Wageningen : Wageningen University - ISBN 9789461739025 - 162
    pectinen - acetylering - pectine lyase - polygalacturonase - karakterisering - methodologie - pectins - acetylation - pectin lyase - polygalacturonase - characterization - methodology

    To reveal the ester distribution patterns in acetylated pectins, an enzymatic fingerprinting method usinga combined endo-polygalacturonase (PG) and pectin lyase (PL) treatment followed by hydrophilicinteraction liquid chromatography coupled to electrospray ionization ion trap mass spectrometry with evaporative light scattering detection was developed. This methodpaved the way for the development of the new quantitative parameters degree of hydrolysis by PG (DHPG) and degree of hydrolysis by PL (DHPL). These parameters distinguished the methylester and acetyl group distribution patterns within different sugar beet pectins (SBPs). In the case of pectin having a degree of methylesterification (DM) of >50 and acetylation of ~20, the above approach was insufficient. Hence, a seconddigestion was introduced using a fungal pectin methylesterase and a PG.More than 60% of the total GalA residues present in three SBPs were recovered as monomer and oligomers after the two digestions. The first digestion of the acid extracted commercial SBP revealed the presence of small blocks of nonesterified GalA residues and segments containing large blocks of PL degradable methylesterified and /or acetylated GalA residues. Blocks of partly methylesterified, non-acetylated GalA residues were recognized after the second digestion. These results show that the acetylation pattern is non-random.

    A pectin acetylesterase (BliPAE) and a pectin methylesterase (BliPME) from Bacillus licheniformis DSM13 were produced, purified and biochemically characterized. The mode of action of BliPAE and BliPME towards acetylated pectins was revealed using the newly developed enzymatic fingerprinting method. BliPAE specifically deacetylates the O-3 linked acetyl groups of nonmethylesterified galacturonic acid residues in the homogalacturan of pectin. BliPME efficiently de-methylesterifies lemon pectins (DM34-76 ®DM 0) and SBPs (DM 30-73 ®DM 14) in a blockwise manner. BliPME is quite tolerant towards the acetyl groups present within the SBPs. For the first time, a comprehensive experimental characterization was directed to enzymes from B. licheniformis having a PAE and a PME activity.

    Structural and water-holding characteristics of untreated and ensiled chicory root pulp
    Ramasamy, U. ; Gruppen, H. ; Schols, H.A. - \ 2013
    Journal of Agricultural and Food Chemistry 61 (2013)25. - ISSN 0021-8561 - p. 6077 - 6085.
    cell-walls - nonstarch polysaccharides - liquid-chromatography - by-products - xyloglucan - cellulose - pectins - fiber - purification - substances
    Cell wall polysaccharides (CWPs) from chicory root pulp (CRP) and the effect of ensiling on CWP structure to reduce the water-holding capacity (WHC) were studied. Sequential extractions of CRP showed that hot water extraction solubilized arabinan-rich pectin and inulin, each representing 6% of all CRP sugars. A significant amount of pectic sugars (46%) rich in uronic acid from CRP was solubilized by chelating agents. Both dilute alkali extraction, which solubilized branched pectin (14% from CRP), and concentrated alkali extraction, which solubilized hemicellulose dominant in yloglucans (2.5%) mostly of the XXXG type and mannan (0.9%), from CRP CWPs seemed to influence the WHC of CRP. Alkali-insoluble residue (39% of CRP sugars) mainly comprised cellulose and some branched pectin (17% from CRP). Ensiling reduced the methyl esterification of pectin, caused degradation of homogalacturonan and rhamnogalacturonan, and possibly modified the xyloglucan, mannan, and glucan network, reducing the WHC from 6 mL/g to 3.4 mL/g.
    Pectin degradation by Botrytis cinerea: recognition of endopolygalacturonases by an Arabidopsis receptor and utilization of Dgalacturonic acid
    Lisha Zhang, Lisha - \ 2013
    Wageningen University. Promotor(en): Pierre de Wit, co-promotor(en): Jan van Kan. - S.l. : s.n. - ISBN 9789461735409 - 188
    botrytis cinerea - plantenziekteverwekkende schimmels - pectinen - degradatie - celwanden - arabidopsis - receptoren - polygalacturonase - galacturonzuur - botrytis cinerea - plant pathogenic fungi - pectins - degradation - cell walls - arabidopsis - receptors - polygalacturonase - galacturonic acid

    The necrotrophic fungal plant pathogenBotrytis cinerea is able to infect over 200 host plants and cause severe damage to crops, both pre- and post-harvest. B. cinerea often penetrates host leaf tissue at the anticlinal cell wall and subsequently grows into and through the middle lamella, which consists mostly of low-methylesterified pectin. Effective pectin degradation thus is important for virulence of B. cinerea. Chapter 1 describes the chemical structures of plant cell wall polysaccharides, the cell wall-associated mechanisms that confer resistance against pathogens, and the microbial enzymes involved in cell wall decomposition. It then discusses the plant cell wall degrading enzymes of pathogenic fungi and illustrates with case studies the process of pectin decomposition by B. cinerea.

    Chapter 2describes the molecular identification and functional characterization of a novel MAMP receptor RBPG1, a Leucine-Rich Repeat Receptor-Like Protein (LRR-RLP), that recognizes fungal endo-polygalacturonases (endo-PGs), in particular the B. cinerea protein BcPG3. Infiltration of the BcPG3 protein into Arabidopsis thaliana accession Col-0 induced a necrotic response. Heat-inactivated protein and a catalytically inactive mutant protein retained the ability to induce necrosis. An 11-amino acid peptide stretch was identified that is conserved among many fungal but not plant endo-PGs. A synthetic peptide comprising this sequence was unable to induce necrosis. A map-based cloning strategy, combined with comparative and functional genomics, led to the identification of the RBPG1 gene, which is required for responsiveness of A. thaliana to the BcPG3 protein. Co-immunoprecipitation experiments demonstrated that RBPG1 and BcPG3 form a complex inNicotiana benthamiana, which also involves the A. thaliana LRR-RLK SOBIR1. The sobir1 mutant plants no longer respond to BcPG3. Furthermore, overexpression of RBPG1 in the BcPG3-non-responsive accession Br-0 did not enhance resistance to a number of microbial pathogens.

    Chapter 3describes the functional, biochemical and genetic characterization of the D-galacturonic acid catabolic pathway in B. cinerea. The B. cinerea genome contains two non-homologous galacturonate reductase genes (Bcgar1 and Bcgar2), a galactonate dehydratase gene (Bclgd1), and a 2-keto-3-deoxy-L-galactonate aldolase gene (Bclga1). Targeted gene replacement of all four genes in B. cinerea, either separately or in combinations, yielded mutants that were affected in growth on D-galacturonic acid, pectate, or pectin as the sole carbon source. The extent of growth reduction of the mutants on pectic substrates was positively correlated to the proportion of D-galacturonic acid present in the pectic substrate. The virulence of these mutants on different host plants is discussed in Chapter 4. These mutants showed reduced virulence on N. benthamiana and A. thaliana leaves, but not on tomato leaves. The cell walls of N. benthamiana and A. thaliana leaves have a higher D-galacturonic acid content as compared to tomato. Additional in vitro growth assays with the knockout mutants suggested that the reduced virulence of D-galacturonic acid catabolism-deficient mutants on N. benthamiana and A. thaliana is not only due to the inability of the mutants to utilize an abundant carbon source as nutrient, but also due to the growth inhibition by catabolic intermediates.

    In Chapter 5, the functional characterization of two putative D-galacturonic acid transporters is presented. Bchxt15 is highly and specifically induced by D-galacturonic acid, whereas Bchxt13 is highly expressed in the presence of all carbon sources tested except for glucose. Subcellular localization of BcHXT13-GFP and BcHXT15-GFP fusion proteins expressed under their native promoter suggests that the fusion proteins are localized in plasma membranes and intracellular vesicles. Knockout mutants in the Bchxt13 and Bchxt15 genes, respectively, were neither affected in their growth on D-galacturonic acid as the sole carbon source, nor in their virulence on tomato and N. benthamiana leaves.

    Chapter 6describes the genome-wide transcriptome analysis in B. cinerea grown in media containing glucose and pectate as sole carbon sources. Genes were identified that are significantly altered in their expression during growth on these two carbon sources. Conserved sequence motifs were identified in the promoters of genes involved in pectate decomposition and D-galacturonic acid utilization. The role of these motifs in regulating D-galacturonic acid-induced expression was functionally analysed in thepromoter of the Bclga1 gene, which encodes one of the key enzymes in the D-galacturonic acid catabolic pathway. The regulation by D-galacturonic acid required the presence of sequences encompassing the GAE1 motif and a binding motif for the pH-dependent transcriptional regulator PacC.

    Chapter 7 provides a general discussion of the results presented in this thesis. A model of the concerted action of pectin degradation and subsequent monosaccharide consumption and co-regulation of gene expression is proposed.

    Designing microcapsules based on protein fibrils and protein - polysaccharide complexes
    Hua, K.N.P. - \ 2012
    Wageningen University. Promotor(en): Erik van der Linden, co-promotor(en): Leonard Sagis. - S.l. : s.n. - ISBN 9789461733801 - 136
    lysozym - ovalbumine - pectinen - aggregatie - inkapseling in microcapsules - lysozyme - ovalbumin - pectins - aggregation - microencapsulation

    Keywords: encapsulation, microcapsule, protein, fibril, protein-polysaccharide complex, controlled release, interfacial rheology, lysozyme, ovalbumin

    This thesis describes the design of encapsulation systems using mesostructures from proteins and polysaccharides. The approach was to first investigate the physical properties of the encapsulating materials (protein fibrils and protein – polysaccharide complexes). Subsequently, microcapsules with tunable release rate and mechanical strength were developed.

    Firstly, the effect of steady shear and turbulent flow on the formation of protein fibrils from lysozyme was studied. We determined the conversion and size distribution of fibrils obtained by heating lysozyme solutions at pH 2. The formation of fibrils was quantified using flow-induced birefringence. The size distribution was fitted using decay of birefringence measurements and Transmission Electron Microscopy. The morphology of Lys fibrils and kinetics of their formation varied considerably depending on the flow applied. With increasing shear or stirring rate, more rod-like and shorter fibrils were obtained, and the conversion into fibrils was increased.

    Secondly, we have investigated the surface rheological properties of oil – water interfaces stabilized by fibrils from lysozyme (long and semi-flexible, and short and rigid ones), fibrils from ovalbumin (short and semi-flexible), lysozyme – pectin complexes, or ovalbumin – pectin complexes. We have compared these properties with those of interfaces stabilized by the native proteins. The surface dilatational and surface shear moduli were determined using an automated drop tensiometer, and a stress controlled rheometer with biconical disk geometry. Results show that interfaces stabilized by protein – pectin complexes have higher surface shear and dilatational moduli than interfaces stabilized by the native proteins only. At most of the experimental conditions, interfaces stabilized by protein fibrils have the highest surface rheological moduli. The difference between long semi-flexible lysozyme fibrils or short rigid lysozyme fibrils is not pronounced in interfacial dilation rheology but significant in interfacial shear rheology. The complex surface shear moduli of interfaces stabilized by long semi-flexible fibrils are about ten times higher than those of interfaces stabilized by short rigid fibrils, over a range of bulk concentrations. Interfaces stabilized by short and more flexible ovalbumin fibrils have a significantly higher surface shear modulus than those stabilized by the somewhat longer and more rigid short lysozyme fibrils.

    Finally, encapsulation systems are developed using layer-by-layer adsorption of food-grade polyelectrolytes on an emulsion droplet template. The first encapsulation system was built with alternating layers of ovalbumin fibrils and high methoxyl pectin. By varying the number of layers, the release of active ingredients can be controlled: increasing the number of layers of the shell from four to eight, decreases the release rate by a factor six.

    The other encapsulation systems were built with alternating layers of protein – pectin complexes and protein fibrils. Two types of proteins (ovalbumin and lysozyme) and three types of fibrils were used: short and semi-flexible from ovalbumin, short and rod-like, and long and semi-flexible from lysozyme. At low number of layers (less than five), microcapsules from ovalbumin complexes and fibrils were stronger than microcapsules prepared from lysozyme complexes and fibrils. Increasing the number of layers, the mechanical stability of microcapsules from lysozyme complexes and fibrils increased significantly, and capsules were stronger than those prepared from ovalbumin complexes and fibrils with the same number of layers. The contour length of the Lys fibrils did not have a significant effect on mechanical stability of the lysozyme complexes and fibrils capsules. These results show that mechanical properties of this type of capsule can be tuned by varying the flexibility of the protein fibrils.

    Aiming for the complete utilization of sugar-beet pulp: Examination of the effects of mild acid and hydrothermal pretreatment followed by enzymatic digestion
    Kuhnel, S. ; Schols, H.A. ; Gruppen, H. - \ 2011
    Biotechnology for Biofuels 4 (2011). - ISSN 1754-6834 - 14 p.
    severity parameter - side-chains - cell-wall - degradation - fermentation - pectins - inhibition - hydrolysis - cellulose - lignocellulosics
    Background - Biomass use for the production of bioethanol or platform chemicals requires efficient breakdown of biomass to fermentable monosaccharides. Lignocellulosic feedstocks often require physicochemical pretreatment before enzymatic hydrolysis can begin. The optimal pretreatment can be different for different feedstocks, and should not lead to biomass destruction or formation of toxic products. Methods - We examined the influence of six mild sulfuric acid or water pretreatments at different temperatures on the enzymatic degradability of sugar-beet pulp (SBP). Results - We found that optimal pretreatment at 140°C of 15 minutes in water was able to solubilize 60% w/w of the total carbohydrates present, mainly pectins. More severe treatments led to the destruction of the solubilized sugars, and the subsequent production of the sugar-degradation products furfural, hydroxymethylfurfural, acetic acid and formic acid. The pretreated samples were successfully degraded enzymatically with an experimental cellulase preparation. Conclusions - In this study, we found that pretreatment of SBP greatly facilitated the subsequent enzymatic degradation within economically feasible time ranges and enzyme levels. In addition, pretreatment of SBP can be useful to fractionate functional ingredients such as arabinans and pectins from cellulose. We found that the optimal combined severity factor to enhance the enzymatic degradation of SBP was between log R'0 = -2.0 and log R'0 = -1.5. The optimal pretreatment and enzyme treatment solubilized up to 80% of all sugars present in the SBP, including =90% of the cellulose.
    Characterizing plant cell wall derived oligosaccharides using hydrophilic interaction chromatography with mass spectrometry detection
    Leijdekkers, A.G.M. ; Sanders, M.G. ; Schols, H.A. ; Gruppen, H. - \ 2011
    Journal of Chromatography. A, Including electrophoresis and other separation methods 1218 (2011)51. - ISSN 0021-9673 - p. 9227 - 9235.
    anion-exchange chromatography - assisted laser-desorption - sugar-beet - acidic oligosaccharides - graphitic carbon - polar compounds - performance - separation - pectins - oligomers
    Analysis of complex mixtures of plant cell wall derived oligosaccharides is still challenging and multiple analytical techniques are often required for separation and characterization of these mixtures. In this work it is demonstrated that hydrophilic interaction chromatography coupled with evaporative light scattering and mass spectrometry detection (HILIC–ELSD–MSn) is a valuable tool for identification of a wide range of neutral and acidic cell wall derived oligosaccharides. The separation potential for acidic oligosaccharides observed with HILIC is much better compared to other existing techniques, like capillary electrophoresis, reversed phase and porous-graphitized carbon chromatography. Important structural information, such as presence of methyl esters and acetyl groups, is retained during analysis. Separation of acidic oligosaccharides with equal charge yet with different degrees of polymerization can be obtained. The efficient coupling of HILIC with ELSD and MSn-detection enables characterization and quantification of many different oligosaccharide structures present in complex mixtures. This makes HILIC–ELSD–MSn a versatile and powerful additional technique in plant cell wall analysis.
    Aardappel kan ook pectine maken
    Trindade, L.M. - \ 2011
    Kennis Online 8 (2011)mei 2011. - p. 8 - 8.
    biobased economy - plantenveredeling - aardappelen - pectinen - nieuwe cultuurgewassen - biobased economy - plant breeding - potatoes - pectins - new crops
    Een aardappel waar fabrikanten caloriearme chips van kunnen maken of die grondstoffen levert voor jam, en reuzengras dat efficienter biobrandstof levert. Bij Wageningen UR, Plant Breeding onderzoeken Luisa Trindade en haar collega’s hoe ze oude en nieuwe gewassen kunnen veranderen in goede leveranciers van grondstoffen voor de bio-economie.
    Hoe veroorzaakt Botrytis rot?
    Kars, I. - \ 2010
    Gewasbescherming 41 (2010)5. - ISSN 0166-6495 - p. 245 - 247.
    botrytis cinerea - pectinen - polygalacturonase - enzymen - plantenziekteverwekkende schimmels - infecties - genen - plantenziekten - botrytis cinerea - pectins - polygalacturonase - enzymes - plant pathogenic fungi - infections - genes - plant diseases
    Als een spore is geland op het plantoppervlak, scheidt Botrytis cinerea enzymen en metabolieten uit waaronder pectine-afbrekende enzymen zoals de zes endopolygalacturonases (BcPGs). Elk van deze BcPGs breken pectine uit de plantencelwanden en middenlamel op hun eigen wijze af. Pectine zit verweven in de plantencelwanden en zorgt voor flexibiliteit van de cellen en de stabiliteit van de structuur van een weefsel. Op het moment dat pectine wordt afgebroken, wordt de verbinding tussen plantencellen verbroken, verliezen de celwanden hun flexibiliteit en het weefsel daarmee haar stabiliteit. Door middel van de BcPGs is Botrytis cinerea dus in staat het plantoppervlak van een gezonde plant binnen te dringen, door de middenlamel te groeien en plantenweefsel om te zetten in schimmelbiomassa en zodoende rot te veroorzaken.
    Influence of pectin characteristics on complexation with ß-lactoglobulin
    Sperber, B.L.H.M. - \ 2010
    Wageningen University. Promotor(en): Fons Voragen; Willem Norde, co-promotor(en): Henk Schols. - [S.l. : S.n. - ISBN 9789085858355 - 174
    pectinen - bèta-lactoglobuline - ladingskenmerken - fysische eigenschappen - chemische eigenschappen - binding (scheikundig) - pectins - beta-lactoglobulin - charge characteristics - physical properties - chemical properties - bonding
    Pectin and proteins are both common food constituents. The type of pectin that forms complexes with protein is known to be of great influence on the structure and stability of liquid foods. Therefore, the aim of this thesis is to investigate the influence of the overall charge and local charge density of pectin on the formation of soluble complexes with β-lactoglobulin (β-lg).
    Combination of state diagrams and binding isotherms shows that a high local charge density of pectin is a prerequisite to form soluble complexes with β-lg at higher ionic strength. A high overall charge of pectin results in the close proximity of the GalA blocks. Therefore, β-Lg neighbours bind close together on pectin with a high overall charge, which leads to lateral repulsion and hence, maxima in the binding constant and the pH where insoluble complexes form with increasing ionic strength.
    The formation of soluble complexes has an enthalpic driving force from electrostatic attraction and an entropic driving force from the release of small counterions from the electric double layer and water molecules from hydrophobic surroundings. A high local charge density, at low ionic strength results in complex formation dominated by an enthalpic driving force. A low local charge density gives a more even distribution between enthalpic and entropic contributions. An increase in ionic strength decreases the enthalpic contribution, with a relative increase in the entropic contribution, supporting the idea of water release from hydrophobic surroundings.
    Adsorption from β-lg–pectin mixtures to a hydrophobic surface leads to low adsorption rates due to a low concentration of free protein. Sequential adsorption of β-lg and pectin shows that low overall charge pectin protrudes more into the solution than high overall charge pectin, resulting in a more negative ζ-potential for low overall charge pectin. After sequential adsorption, β-lg is most stable against wash-out with a terminal pectin layer.
    Branched arabino-oligosaccharides isolated from sugar beet arabinan
    Westphal, Y. ; Kuhnel, S. ; Waard, P. de; Hinz, S.W.A. ; Schols, H.A. ; Voragen, A.G.J. ; Gruppen, H. - \ 2010
    Carbohydrate Research : an international journal 345 (2010)9. - ISSN 0008-6215 - p. 1180 - 1189.
    cell-walls - structural characterization - feruloyl oligosaccharides - polysaccharides - acid - nmr - pectins - pulp
    Sugar beet arabinan consists of an a-(1,5)-linked backbone of l-arabinosyl residues, which can be either single or double substituted with a-(1,2)- and/or a-(1,3)-linked l-arabinosyl residues. Neutral branched arabino-oligosaccharides were isolated from sugar beet arabinan by enzymatic degradation with mixtures of pure and well-defined arabinohydrolases from Chrysosporium lucknowense followed by fractionation based on size and analysis by MALDI-TOF MS and HPAEC. Using NMR analysis, two main series of branched arabino-oligosaccharides have been identified, both having an a-(1,5)-linked backbone of l-arabinosyl residues. One series carries single substituted a-(1,3)-linked l-arabinosyl residues at the backbone, whereas the other series consists of a double substituted a-(1,2,3,5)-linked arabinan structure within the molecule. The structures of eight such branched arabino-oligosaccharides were established.
    Chemical, physical and biological features of Okra pectin
    Sengkhamparn, N. - \ 2009
    Wageningen University. Promotor(en): Fons Voragen, co-promotor(en): Henk Schols; T. Sajjaanantakul. - [S.L. : S.n. - ISBN 9789085855293 - 176
    pectinen - okra's - karakterisering - fysicochemische eigenschappen - pectins - okras - characterization - physicochemical properties
    In Thailand, many plants have been used as vegetables as well as for traditional
    medicine. Okra, Abelmoschus esculentus (L.) Moench, is an example of such a plant.
    Examples for the medical use are treatment of gastric irritation, treatment of dental
    diseases, lowering cholesterol level and preventing cancer. These biological activities are
    ascribed to polysaccharide structures of okra in particular pectin structures. However, the
    precise structure of okra pectins and also of other polysaccharides in okra pods have been
    lacking so far.
    In order to obtain detailed information of the different polysaccharides present in
    okra, okra cell wall material was prepared from the pulp of okra pods and was then
    sequentially extracted with hot buffer, chelating agent, diluted alkali and concentrated
    alkali. The sugar (linkage) composition indicated that okra cell wall contained, next to
    cellulose, different populations of pectins and hemicelluloses.
    The pectic polysaccharides were mainly obtained in the first three extracts having
    slightly different chemical structures. The okra pectin extracted by hot buffer was almost a
    pure rhamnogalacturonan (RG) I with a high degree of acetylation (DA), covalently linked
    to a minor amount of homogalacturonan (HG) having a high degree of methyl esterification
    (DM). The chelating agent extractable pectin and the diluted alkali extractable pectin
    predominantly contained HG with only minor amounts of RG I. Okra pectins extracted by
    hot buffer and with chelating agent had in common that both contained highly branched RG
    I with very short side chains containing not more than 3 galactosyl units attached to the
    rhamnosyl residues in RG I backbone. Chelating agent extracted okra pectins also carried
    arabinan and arabinogalactan type II as neutral side chains and these side chains were even
    more abundantly present in the diluted alkali extracted okra pectin.
    The hemicellulosic polysaccharides ended up in concentrated alkali extract. From
    the sugar (linkage) composition and enzymatic degradation studies using pure and well
    defined enzymes, it was concluded that this fraction contained a XXXG–type xyloglucan
    and 4-methylglucuronoxylan. The cellulosic polysaccharides were retained in the residue.
    The okra hot buffer extractable RG I having a high level of acetyl substitution
    appeared to be very well degradable by rhamnogalacturonan hydrolase which was known to
    be hindered completely by acetylated substrates. In contrast, an acetylated galacturonic
    acid-specific rhamnogalacturonan acetyl esterase was unable to remove acetyl groups from
    the RG I molecule of hot buffer extracted okra pectin. For these reasons, the precise
    position of the acetyl groups present on enzymatically released oligomers were determined
    by Electron Spray Ionization Ion Trap Mass Spectrometry (ESI-IT-MS) and Nuclear
    Magnetic Resonance (NMR) spectroscopy. The acetyl groups were found to be
    predominantly located at position O-3 of the rhamnosyl moiety, while the methyl esters
    seemed to be present only on the HG part of the hot buffer extracted okra pectin. Another
    novelty of okra RG-I was the presence of terminal alpha-linked galactosyl substitution at
    position O-4 of the rhamnosyl residues within the RG I backbone. These specific features
    (acetylated rhamnosyl- and alpha-galactosyl-substitutions) were almost absent in the
    chelating agent extracted okra pectin where more commonly known substitutions were
    present, including acetylated galacturonosyl residues in the RG I backbone. The unique
    structure features of hot buffer extracted okra pectin led to the assumption that these
    features may contribute to the rather typical physical properties as well as to the biological
    properties found for okra pectin.
    In order to understand the effect of the specific structural features of RG I on its
    physical properties, the rheological properties of hot buffer extracted okra pectin were
    determined and compared to those found for chelating agent extracted okra pectin and for
    pectins from other plant materials as reported in the literature. The solutions of hot buffer
    extracted okra pectin showed a high viscosity and predominant elastic behaviour which
    most probably is caused by strong hydrophobic associations through its acetylated
    rhamnosyl residues rather than by methyl esterified galacturonosyl residues as is commonly
    the case for pectins. The removal of acetyl groups and methyl esters decreased the
    association of the pectin molecules as observed by the light scattering experiment, meaning
    that not only viscosity and rheological properties but also association of pectin molecules
    were as result of both hydrophobic interactions and charge effects.
    The effect of the position of acetyl groups on the bioactivity of okra pectin was
    also determined. The complement-fixing activity of okra pectins was found to be affected
    by many factors like e.g. the presence of acetyl groups, the size of RG segments and the presence of terminal alpha galactosyl groups and even the three dimensional conformation
    of the molecules. The hot buffer extracted okra pectin was also examined for its potential to
    modify surfaces of medical devices and implants. The results showed that okra pectin can
    be used in coating medical device since it promotes cell apoptosis and shows no
    macrophage activation.
    The knowledge described in this thesis provided us with novel information on the
    unique structures of okra pectins and may lead to a better understanding of the functional
    properties of okra polysaccharides in general and okra pectin in particular and to optimize
    the use of okra pectins within the food industry and in medical applications. However,
    despite our efforts, at the moment the dependency of the (bio) functionality of okra pectins
    on the precise chemical structure are not yet completely understood.
    Pectins and pectinases
    Schols, H.A. ; Visser, R.G.F. ; Voragen, A.G.J. - \ 2009
    Wageningen : Wageningen Academic Publishers - ISBN 9789086861088 - 331
    pectinen - biochemie - plantaardige producten - voedselsamenstelling - pectins - biochemistry - plant products - food composition
    Assessment of the Production of Oligomeric Compounds from Sugar Beet Pulp
    Martinez, M. ; Gullon, B. ; Schols, H.A. ; Alonso, J.L. ; Parajo, J.C. - \ 2009
    Industrial & Engineering Chemistry Research 48 (2009)10. - ISSN 0888-5885 - p. 4681 - 4687.
    human gut microflora - prebiotic properties - oligosaccharides - autohydrolysis - liquors - pectins - barley - husks
    In order to obtain pectin-derived oligosaccharides (mainly arabinooligosaccharides and oligogalacturonides), samples of sugar beet pulp (SBP) were subjected to hydrothermal processing under nonisothermal conditions. Experiments carried out to reach temperatures in the range 160¿175 °C (corresponding to values of the severity factor R0 in the range 287¿835 min) led to comparatively high concentrations of both oligogalacturonides and arabinooligosaccharides. When SBP was treated to achieve a maximum temperature of 160 °C (R0 = 287 min) or 163 °C (R0 = 357 min), the overall amount of oligomers present in the reaction liquors recovered by pressing accounted for 31.2 and 29.9 g/100 g of oven-dried SBP, respectively, with a limited amount of nonvolatile impurities (about 0.15 g/g of oven-dried matter) and a mass ratio of arabinooligosaccharides/oligogalacturonides of about 1:1. Spent solids were washed with water, and the washing liquors were assayed for oligomers. Recovery of washing liquors would increase the overall yield process by 10%, to reach near 33 g/100 g of oven-dried SBP. Washed spent solids (with increased cellulose content) were obtained as a process byproduct.
    Structural characterization of native pectins
    Coenen, G.J. - \ 2007
    Wageningen University. Promotor(en): Fons Voragen, co-promotor(en): Henk Schols. - [S.l.] : S.n. - ISBN 9789085047797 - 152
    pectinen - karakterisering - chemische structuur - massaspectrometrie - degradatie - capillaire electroforese - pectins - characterization - chemical structure - mass spectrometry - degradation - capillary electrophoresis
    Pectine wordt in levensmiddelen vooral gebruikt als geleermiddel, stabilisator of verdikkingsmiddel in producten zoals jam, yoghurtdranken, vruchten-zuiveldranken en ijs. Daarnaast is er in toenemende mate interesse in het mogelijk gezondheidbevorderend effect van dit polysaccharide. Kennis van de exacte structuur zal bijdragen aan het begrip van de fysiologische functie van pectine in de plant en aan een verdere optimalisering van industriële en medische toepassingen van dit polymeer. Om meer inzicht te krijgen in de structuur werden nieuwe LC-MS en CE-MS methoden ontwikkeld, waarmee verbindingen tussen verschillende structuurelementen konden worden aangetoond. Als gevolg van de verkregen inzichten over de opbouw van pectine, wordt een aanpassing aan het structuurmodel van pectine voorgesteld, waarbij homogalacturonan ketens zowel lineair als vertakt aan rhamnogalacturonan I worden gepositioneerd. De ontwikkelde methoden, kunnen worden toegepast in onderzoek gericht op de opheldering van techno- en biofunctionele eigenschappen van complexe polysaccharidestructuren.
    Check title to add to marked list
    << previous | next >>

    Show 20 50 100 records per page

     
    Please log in to use this service. Login as Wageningen University & Research user or guest user in upper right hand corner of this page.