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    Replacing lactose from calf milk replacers : effects on digestion and post-absorptive metabolism
    Gilbert, M.S. - \ 2015
    Wageningen University. Promotor(en): Wouter Hendriks, co-promotor(en): Walter Gerrits; Henk Schols. - Wageningen : Wageningen University - ISBN 9789462576032 - 171
    vleeskalveren - lactose - kunstmelk - polysacchariden - glucose - fructose - glycerol - zetmeelvertering - metabolisme - fermentatie - kalvervoeding - diervoeding - voedingsfysiologie - veal calves - lactose - filled milk - polysaccharides - glucose - fructose - glycerol - starch digestion - metabolism - fermentation - calf feeding - animal nutrition - nutrition physiology

    Summary PhD thesis Myrthe S. Gilbert

    Replacing lactose from calf milk replacers – Effects on digestion and post-absorptive metabolism

    Veal calves are fed milk replacer (MR) and solid feed. The largest part of the energy provided to veal calves originates from the MR. Calf MR contains 40 to 50% lactose, originating from whey, a by-product from cheese production. High and strongly fluctuating dairy prices are a major economic incentive to replace lactose from the calf MR by alternative energy sources. The objective of this thesis was to study the effects of replacing lactose from calf MR on nutrient digestion and fermentation and post-absorptive metabolism.

    In Chapter 2 and 3, four starch products (SP) were evaluated for replacing lactose. The four SP differed in size and branching, and consequently required different ratios of starch-degrading enzymes for their complete hydrolysis to glucose. Gelatinized starch required α-amylase and (iso)maltase; maltodextrin required (iso)maltase and α-amylase; maltodextrin with α-1,6-branching required isomaltase, maltase and α-amylase and maltose required maltase. In Chapter 2, adaptation to these SP was assessed during 14 weeks, using a within-animal titration study. Forty male Holstein-Friesian calves (n = 8 per treatment) were assigned to either a lactose control MR or one of four titration strategies, each testing the stepwise exchange of lactose for one of the SP. For control calves, fecal dry matter (DM) content and fecal pH did not change over time. The response in fecal DM content and fecal pH in time did not differ between SP treatments and decreased linearly with 0.57% and 0.32 per week, respectively, where one week corresponded to an increase in SP inclusion of 3%. This indicates that the capacity for starch digestion was already exceeded at low inclusion levels, resulting in SP fermentation. All SP required maltase to achieve complete hydrolysis to glucose and it was, therefore, suggested that maltase is the rate-limiting enzyme in starch digestion in milk-fed calves.

    Following the titration, a fixed inclusion level of 18% of the SP in the MR was applied. Effects on starch-degrading enzyme activity, nutrient disappearance, SP fermentation and jugular glucose appearance were measured (Chapter 3). Lactase activity in the brush border was high in the proximal small intestine of all calves, resulting in a high apparent ileal disappearance of lactose (≥ 99% of intake). Maltase and isomaltase activities in the brush border were not increased for any of the SP treatments. Luminal α-amylase activity was lower in the proximal small intestine but greater in the distal small intestine of SP-fed calves compared to control calves. This amylase activity in the distal small intestine of SP-fed calves might have been of microbial origin. Apparent SP disappearance did not differ between SP treatments. The difference between apparent ileal (62%) and total tract (99%) SP disappearance indicated substantial SP fermentation in the large intestine (37% of intake). In addition, total tract SP fermentation was quantified using fecal 13C excretion which originated from the naturally 13C-enriched corn SP. Total tract SP fermentation averaged 89% of intake, regardless of SP treatment. MR leaking into the reticulorumen was measured as the recovery of Cr in the reticulorumen at slaughter after feeding MR pulse-dosed with Cr 4h prior to slaughter. MR leaking into the reticulorumen averaged 11% for SP-fed calves. By difference, this leaves 41% of the SP intake fermented in the small intestine. This coincided with increased fecal nitrogen (N) and DM losses for SP-fed calves. However, apparent total tract crude fat disappearance tended to increase when replacing lactose with SP. The substantial SP fermentation indicates that only 10% of the SP intake was enzymatically hydrolyzed and absorbed as glucose. This was in agreement with the marginal increase in 13C enrichment in peripheral plasma glucose after feeding naturally 13C-enriched gelatinized starch and maltose, compared to a clear increase after feeding naturally 13C-enriched lactose to control calves. It was concluded that fermentation, rather than enzymatic digestion, is the main reason for small intestinal starch disappearance in milk-fed calves. The expected decrease in growth performance with such extensive SP fermentation is partially compensated by the greater crude fat digestion and possibly by a reduced urinary glucose excretion when replacing lactose with SP.

    Glucose, fructose and glycerol do not require enzymatic hydrolysis and can be absorbed directly from the small intestine. However, these lactose replacers might differentially affect glucose and insulin metabolism and with that energy partitioning. The effects of partly replacing lactose with glucose, fructose or glycerol on energy and N partitioning and glucose homeostasis and insulin sensitivity were, therefore, studied in Chapter 4 and 5. Forty male Holstein-Friesian calves either received a lactose control MR or a MR in which one third of the lactose was replaced with glucose, fructose or glycerol (n = 10 per treatment). Energy and N retention were not affected by MR composition. Fructose absorption from the small intestine was incomplete resulting in fructose fermentation. This resulted in fecal losses of DM, energy and N and the lowest numerical energy and N retention for fructose-fed calves. Postprandial plasma concentrations of glucose exceeded the renal threshold for glucose in glucose-fed calves and control calves, which resulted in urinary glucose excretion. Glycerol was likely excreted with the urine of glycerol-fed calves. Oxidation of glucose, fructose and glycerol was quantified by feeding a single dose of [U-13C]glucose, [U-13C]fructose or [U-13C]glycerol with the MR and subsequently measuring 13CO2 production. Oxidation of lactose replacers did not differ between lactose replacers and averaged 72% of intake. However, the time at which the maximum rate of oxidation was reached was delayed for fructose-fed compared to glucose-fed and glycerol-fed calves, indicating that fructose was converted into other substrates before being oxidized. Conversion of fructose and glycerol into glucose was confirmed by an increase in 13C enrichment of peripheral plasma glucose after feeding [U-13C]fructose and [U-13C]glycerol, respectively. Insulin sensitivity did not differ between MR treatments, but was already low at the start of the experiment at 15 weeks of age and remained low throughout the experiment. It was concluded that glucose and glycerol can replace one third of the lactose from the calf MR, but that inclusion of fructose should be lower to prevent incomplete absorption from the small intestine.

    In literature and the studies in this thesis, high inter-individual variation in growth performance was found in veal calves. The experiment described in Chapter 6 was, therefore, designed to assess the predictability of later life growth performance by charactering calves in early life. In addition, it was examined whether the ability of calves to cope with MR in which lactose is partially replaced by alternative energy sources can be predicted. From 2 to 11 weeks of age, male Holstein-Friesian calves were fed a lactose control MR and solid feed according to a practical feeding scheme and were characterized individually using targeted challenges related to feeding motivation, digestion, post-absorptive metabolism, immunology, behavior and stress. Based on the results in Chapter 4, a combination of glucose, fructose and glycerol in a 2:1:2 ratio was used to replace half of the lactose from the MR (GFG). From 11 to 27 weeks of age, calves received a lactose control MR or the GFG MR (n = 65 per treatment). Growth performance from 11 to 27 weeks of age tended to be lower for GFG-fed than for control calves (-25 g/d). Measurements in early life explained 12% of the variation in growth performance in later life. However, this was mainly related to variation in solid feed refusals. When growth performance was adjusted to equal solid feed intake, only 4% of the variation in standardized growth performance in later life, reflecting feed efficiency, could be explained by early life measurements. This indicates that > 95% of the variation in feed efficiency in later life could not be explained by early life characterization. It is hypothesized that variation in health status explains substantial variation in feed efficiency in veal calves. Significant relations between fasting plasma glucose concentrations, fecal dry matter and fecal pH in early life and feed efficiency in later life depended on MR composition. These measurements are, therefore, potential tools for screening calves in early life on their ability to cope with a MR in which half of the lactose is replaced by glucose, fructose and glycerol (in a 2:1:2 ratio).

    The studies reported in this thesis demonstrate that glycerol, glucose and a combination of glucose, fructose and glycerol in a 2:1:2 ratio are promising lactose replacers. The effects of replacing lactose by other carbohydrate or energy sources described in this thesis are required to evaluate the potential of lactose replacers for inclusion in calf milk replacers and provide input for feed evaluation for calves and ruminants.

    Ercella succinigenes gen. nov., sp. nov., an anaerobic succinate-producing bacterium
    Gelder, A.H. van; Sousa, D.Z. ; Rijpstra, W.I. ; Damsté, J.S. ; Stams, A.J.M. ; Sanchez Andrea, I. - \ 2014
    International Journal of Systematic and Evolutionary Microbiology 64 (2014)7. - ISSN 1466-5026 - p. 2449 - 2454.
    ribosomal-rna genes - acid - heterogeneity - fermentation - sequences - biofuels - glycerol - industry - operons - genomes
    A novel anaerobic succinate-producing bacterium, strain ZWBT, was isolated from sludge collected from a biogas desulfurization bioreactor (Eerbeek, the Netherlands). Cells were non-spore-forming, motile, slightly curved rods (0.4–0.5 µm in diameter and 2–3 µm in length), and stained Gram-negative. The temperature range for growth was 25–40 °C, with an optimum at 37 °C. The pH range for growth was 7.0–9.0, with an optimum at pH 7.5. Strain ZWBT was able to ferment glycerol and several carbohydrates mainly to H2, succinate and acetate. Sulfur and fumarate could be used as electron acceptors by strain ZWBT. The G+C content of the genomic DNA was 37.6 mol%. The most abundant fatty acids were iso-C14¿:¿0 and iso-C16¿:¿0 DMA. On the basis of 16S rRNA gene sequence similarity, strain ZWBT belongs to the family Ruminococcaceae and it is distantly related to Saccharofermentans acetigenes JCM 14006T (92.1¿%). Based on the physiological features and phylogenetic analysis, strain ZWBT represents a novel species of a new genus, for which the name Ercella succinigenes gen. nov., sp. nov. is proposed. The type strain of Ercella succinigenes is ZWBT (¿=¿DSM 27333T¿=¿JCM 19283T).
    Korte verblijftijd haalbaar bij mestvergisting
    Timmerman, M. ; Eekert, M. ; Riel, J.W. van; Schuman, E. - \ 2013
    V-focus 10 (2013)6. - ISSN 1574-1575 - p. 42 - 43.
    veehouderij - mestvergisting - biogas - gasproductie - fermentatie - duur - glycerol - biobased economy - warmtekrachtkoppeling - livestock farming - manure fermentation - biogas - gas production - fermentation - duration - glycerol - biobased economy - cogeneration
    Vergisting van mest bij verblijftijden van korter dan 15 dagen is haalbaar, maar mestsoort en mestkwaliteit blijken een groot effect te hebben op de biogasproductie bij deze korte verblijftijden. Het is mogelijk om bij deze korte verblijftijd een kleine hoeveelheid (<5%) glycerine toe te voegen waardoor de biogasproductie sterk toeneemt, zodat er een 2 tot 3 keer zo grote WKK kan worden neergezet als bij pure mestvergisting. Maar de biogasproductie van de glycerine hangt wel af van de mestkwaliteit.
    Mestvergisting bij korte verblijftijden
    Timmerman, M. ; Eekert, M.H.A. van; Riel, J.W. van; Schuman, E. - \ 2013
    Lelystad : Wageningen UR Livestock Research (Rapport / Wageningen UR Livestock Research 729) - 19
    mestvergisting - fermentatie - biogas - gasproductie - glycerol - tijd - biobased economy - manure fermentation - fermentation - biogas - gas production - glycerol - time - biobased economy
    In four CSTR laboratory reactors research has been conducted into the effect of reduction of the retention time on the biogas production from pig and cattle slurry and the volatile fatty acid content in the digester. Further, the effect of adding a small amount of glycerine on the retention time and the volatile fatty acid content in the digester has been researched.
    Lactobacillus plantarum possesses the capability for wall teichoic acid backbone alditol switching
    Bron, P.A. ; Tomita, S. ; Swam, I. van; Remus, D.M. ; Meijerink, M. ; Wels, M. ; Okada, S. ; Wells, J. ; Kleerebezem, M. - \ 2012
    Microbial Cell Factories 11 (2012). - ISSN 1475-2859
    aureus nasal colonization - complete genome sequence - toll-like receptor-2 - staphylococcus-aureus - bacillus-subtilis - lipoteichoic acid - cell-wall - peptidoglycan - biosynthesis - glycerol
    Background - Specific strains of Lactobacillus plantarum are marketed as health-promoting probiotics. The role and interplay of cell-wall compounds like wall- and lipo-teichoic acids (WTA and LTA) in bacterial physiology and probiotic-host interactions remain obscure. L. plantarum WCFS1 harbors the genetic potential to switch WTA backbone alditol, providing an opportunity to study the impact of WTA backbone modifications in an isogenic background. Results - Through genome mining and mutagenesis we constructed derivatives that synthesize alternative WTA variants. The mutants were shown to completely lack WTA, or produce WTA and LTA that lack D-Ala substitution, or ribitol-backbone WTA instead of the wild-type glycerol-containing backbone. DNA micro-array experiments established that the tarIJKL gene cluster is required for the biosynthesis of this alternative WTA backbone, and suggest ribose and arabinose are precursors thereof. Increased tarIJKL expression was not observed in any of our previously performed DNA microarray experiments, nor in qRT-PCR analyses of L. plantarum grown on various carbon sources, leaving the natural conditions leading to WTA backbone alditol switching, if any, to be identified. Human embryonic kidney NF-¿B reporter cells expressing Toll like receptor (TLR)-2/6 were exposed to purified WTAs and/or the TA mutants, indicating that WTA is not directly involved in TLR-2/6 signaling, but attenuates this signaling in a backbone independent manner, likely by affecting the release and exposure of immunomodulatory compounds such as LTA. Moreover, human dendritic cells did not secrete any cytokines when purified WTAs were applied, whereas they secreted drastically decreased levels of the pro-inflammatory cytokines IL-12p70 and TNF-a after stimulation with the WTA mutants as compared to the wild-type. Conclusions - The study presented here correlates structural differences in WTA to their functional characteristics, thereby providing important information aiding to improve our understanding of molecular host-microbe interactions and probiotic functionality
    Monovergisting varkensmest op boerderijschaal = Fermenting pig manure on farm scale
    Kasper, G.J. ; Peters, B. - \ 2012
    Lelystad : Wageningen UR Livestock Research (Rapport / Wageningen UR Livestock Research 632) - 29
    varkenshouderij - varkensmest - mestvergisting - glycerol - gistingstanken - vergelijkend onderzoek - biobased economy - pig farming - pig manure - manure fermentation - glycerol - digesters - comparative research - biobased economy
    Technische en economische berekeningen van vergisting van varkensmest zonder en met glycerine zijn weergegeven na praktijkproeven op boerderijschaal op VIC Sterksel met twee monovergisters, een mini-WKK (MAN, 60 kW) en een minigasturbine (Capstone, 60 kW). De Microferm van HoSt en de UDR-fermenter (Röring, Duitsland) zijn als monovergister onderzocht.
    On the applicability of Flory-Huggins theory to ternary starch-water-solute systems
    Habeych Narvaez, E.A. ; Guo, X. ; Soest, J.J.G. van; Goot, A.J. van der; Boom, R.M. - \ 2009
    Carbohydrate Polymers 77 (2009)4. - ISSN 0144-8617 - p. 703 - 712.
    differential scanning calorimetry - crystalline polymorph - thermoplastic starch - solvent interactions - phase-transitions - potato starch - wheat-starch - dry starch - gelatinization - glycerol
    The effects of glucose and glycerol on gelatinization of highly concentrated starch mixtures were investigated with wide-angle X-ray scattering and differential scanning calorimetry. The gelatinization/melting of starch was found to be a two step process. In the first step the granule swells at low temperatures (i.e., 30¿50 °C), which is followed by a solvent¿temperature cooperative step that induces loss of crystallinity. The results were interpreted with an extended form of the adapted Flory equation. The values of the model parameters (, ¿Hu, ¿12, ¿13, and ¿23) obtained were similar to the values reported in the literature. Ternary phase diagrams were constructed with melting lines representing fully gelatinized starch. The crystalline region of starch with glucose was larger than with glycerol. This could be understood from the differences in ¿13 (solute¿solvent interaction). The extended form of Flory¿Huggins model somewhat under predicts the experimental values of the gelatinization process. Comparing the Flory¿Huggins model with experiments led to the conclusion that Flory equation is a useful tool to interpret and predict the gelatinization and melting behaviour of ternary starch-based systems. But the experiments are complex, the systems are often not in true equilibrium and other disturbing effects are easily encountered. Therefore one should be cautious in the translation of experimental results to the thermodynamics of gelatinization in multicomponent systems
    Bulk chemicals from biomass
    Haveren, J. van; Scott, E.L. ; Sanders, J.P.M. - \ 2008
    Biofuels Bioproducts and Biorefining 2 (2008)1. - ISSN 1932-104X - p. 41 - 57.
    klebsiella-pneumoniae - zeolite catalysts - 2,3-butanediol - ethanol - lignin - 1,3-propanediol - dehydration - conversion - glycerol - butanol
    Given the current robust forces driving sustainable production, and available biomass conversion technologies, biomass-based routes are expected to make a significant impact on the production of bulk chemicals within 10 years, and a huge impact within 20-30 years. In the Port of Rotterdam there is a clear short-term (0-10 year) substitution potential of 10-15 % of fossil oil-based bulk chemicals by bio-based bulk chemicals, especially for oxygenated bulk chemicals, such as ethylene glycol and propylene glycol, iso-propanol and acetone, butylene and methylethylketone and for the replacement of methyl tertiary butyl ether (MTBE) by ethyl tertiary butyl ether (ETBE). Glycerin, as a byproduct of biodiesel production, is a very favorable short-term option for the production of ethylene and propy-lene glycols in the Port of Rotterdam. In the mid-term (10-20 years) there is clear potential for a bio-based production of ethylene, acrylic acid and N-containing bulk chemicals such as acrylonitrile, acrylamide and -caprolactam. Technologies involving direct isolation of aromatic building blocks from biomass, or the conversion of sugars or lignin to aromatics are still in their infancy. Biorefineries that are being started up today will form the stepping stones toward the chemicals mentioned above if we learn to upgrade their side streams. For main ports like the Port of Rotterdam, these developments imply that it has to consider in much closer detail those facilities it has to offer for a more bio-based chemistry and economy. © 2007 Society of Chemical Industry and John Wiley & Sons, Ltd
    Improvement of parameters of freezing medium and freezing protocol for bull sperm using two osmotic supports.
    Chaveiro, A. ; Machado, A.L. ; Frijters, A. ; Engel, B. ; Woelders, H. - \ 2006
    Theriogenology 65 (2006)9. - ISSN 0093-691X - p. 1875 - 1890.
    lipid phase-transitions - bovine spermatozoa - cooling rate - egg-yolk - survival - glycerol - plasma - frozen - semen - cryopreservation
    The aim of this study was to improve the freezing protocol of bull sperm, by investigating the influence on sperm viability after freeze/thawing of different freezing medium components, as well as the effect of cooling rates in the different stages of the cooling protocol, in single factor experiments. The experimental variables were: (1) salt-based versus a sugar-based medium (Tris versus sucrose); (2) glycerol concentration; (3) detergent (Equex) concentration; (4) presence of bicarbonate; (5) rate of cooling from 22 °C to holding temperature (CR1); (6) holding temperature (HT); (7) rate of cooling from holding temperature to -6 °C (CR2); (8) rate of cooling from -10 to -100 °C (CR3). All experiments were performed using five bulls per experiment (three ejaculates per bull). Sperm motility after freezing and thawing was assessed by CASA system, and sperm membrane integrity was assessed by flow cytometry. Sucrose-based medium did not offer a clear significant benefit compared to Tris medium. The concentration of Equex that gave the best results in Tris-based media group and sucrose-based media group was in a range between 2-7 and 4-7 g/l, respectively. In both media groups, a glycerol concentration of 800 mM was the best in any post-thaw viability parameters. In the Tris media group, the presence of bicarbonate had a negative effect on sperm viability. CR1 and CR2 had no significant effect on any of the post-thaw sperm viability parameters, but a CR1 = 0.2 °C/min and CR2 = 4 °C/min appeared to give better results in both media. The holding temperature (HT) that gave the best results was found to be in the range of 5-9 °C. There was a significant disadvantage of using a low CR3 of 10 °C/min, while 150 °C/min appeared to be the best cooling rate for either medium
    Polyol accumulation by Aspergillus oryzae at low water activity in solid-state fermentation
    Ruijter, G.J.G. ; Visser, J. ; Rinzema, A. - \ 2004
    Microbiology 150 (2004). - ISSN 1350-0872 - p. 1095 - 1101.
    d-arabitol dehydrogenase - saccharomyces-cerevisiae - hyperosmotic stress - candida-albicans - glycerol - nidulans - pathway - growth - niger - expression
    Polyol accumulation and metabolism were examined in Aspergillus oryzae cultured on whole wheat grains or on wheat dough as a model for solid-state culture. In solid-state fermentation (SSF), water activity (a(w)) is typically low resulting in osmotic stress. In addition to a high level of mannitol, which is always present in the cells, A. oryzae accumulated high concentrations of glycerol, erythritol and arabitol at relatively low a(w) (0(.)96-0(.)97) in SSF. Accumulation of such a mixture of polyols is rather unusual and might be typical for SSF. A. oryzae mycelium accumulating various polyols at low aw contained at least four distinct polyol dehydrogenases with highest activities toward glycerol, erythritol, D-arabitol and mannitol. NADP(+)-dependent glycerol dehydrogenase activity correlated very well with glycerol accumulation. A similar correlation was observed for erythritol and NADP(+)-erythritol dehydrogenase suggesting that NADP(+)-dependent glycerol and erythritol dehydrogenases are involved in biosynthesis of glycerol and erythritol, respectively, and that these enzymes are induced by osmotic stress.
    Enzymatic acylglycerol synthesis in membrane reactor systems
    Padt, A. van der - \ 1993
    Agricultural University. Promotor(en): K. van 't Riet. - S.l. : Van der Padt - ISBN 9789054851264 - 151
    derivaten - alcoholen - glycerol - acylglycerolen - diacylglycerolen - triacylglycerolen - chemische reacties - membranen - omgekeerde osmose - ultrafiltratie - fermentatie - voedselbiotechnologie - vetzuren - carbonzuren - derivatives - alcohols - glycerol - acylglycerols - diacylglycerols - triacylglycerols - chemical reactions - membranes - reverse osmosis - ultrafiltration - fermentation - food biotechnology - fatty acids - carboxylic acids

    Up till twenty years ago, only chemical modifications of agricultural oils for novel uses were studied. Because of the instability of various fatty acids, enzymatic biomodifications can have advantages above the chemical route. Nowadays, enzymatic catalysis can be used for the modification of oils and fats. One way of biomodification is the enzymatic esterification of glycerol with fatty acid for the synthesis of mono- and triacylglycerols. Monoesters (monoacylglycerols) are used as emulsifiers in food and in cosmetics, tailor made triesters (triacylglycerols) are used to adjust the melting range of foods and cosmetics. This thesis describes a number of membrane reactor systems for the enzymatic esterification of glycerol with decanoic acid in hexadecane as solvent. Description and modelling of the kinetics and thermodynamic equilibrium have resulted in reactor concepts to reach the objective of mono- and triester synthesis.

    The basic reactor studied is a two-phase immobilized enzyme membrane reactor. In the membrane reactor, lipase from Candida ragosa is immobilized at the inner fibre side of a hydrophilic hollow fibre module. Decanoic acid in n-hexadecane is circulated at the same side, meanwhile a water-glycerol phase is circulated at the shell side. The glycerol diffuses through the membrane matrix allowing the synthesis to take place at the interface. The water produced diffuses backwards.

    Chapter 2 describes the enzymatic esterification of decanoic acid with glycerol for an emulsion system and for a hydrophilic membrane system. In a two-phase system, the enzyme activity is related to the oil-phase volume, the interface area and the enzyme load. The rate per unit interface area of the membrane system approximates the rate measured in an emulsion system. This implies that the cellulose membrane does not affect the esterification. Another consequence is that the activity per oil-phase volume is only specific surface area related, therefore a hollow fibre device is desirable. The optimum enzyme load in the membrane system is half of that in the emulsion system.

    The enzyme stability in glycerol-water mixtures is described in chapter 3. The activity of lipase from Candida rugosa with time can be described with a two-step model, assuming the native lipase reversibly altering its conformation to a form having no activity. The reversibility is experimentally verified. Both, the native and inactive form do inactivate irreversible at the same time to a completely inactive form. The inactivation is a function of the glycerol concentration. The activity of immobilized enzyme is reduced to the same level of activity as is found for free lipase.

    Not only activity and stability of the enzymatic system are of importance, also the equilibrium ester concentrations must be known in the non-ideal two-phase system. Chapter 4 presents the program TREP (Two-phase Reaction Equilibrium Prediction). With the use of measured thermodynamic activity based equilibrium constants, mass balances and the UNIFAC group contribution method, TREP predicts the equilibrium product and substrate concentrations for given initial amounts. Equilibrium predictions show that an excess of triesters can be obtained only at low water activity conditions, in this case an one-phase system is predicted. Predictions show that pure monoesters cannot be obtained in a two-phase system of decanoic acid-hexadecane phase and a glycerol-water phase, even with a high glycerol to fatty acid ratio. This is experimentally verified.

    From the knowledge gathered in these chapters, two membrane reactor systems are designed, one membrane reactor for the triester production and a second membrane reactor system equipped with an in-line adsorption column for the synthesis of monoesters.

    Chapter 5 describes a pervaporation system in which an excess of triesters can be synthesized at low water activity conditions. Lipase is immobilized onto the lumen side of a cellulose membrane where the organic phase is present. At the shell side, air circulates and the water activity is controlled with the use of a condenser. The lipase catalyzed esterification of decanoic acid with partial glycerides is studied in this reactor. In agreement with the predictions made in chapter 4, an excess of triacylglycerols, is obtained at low water activity conditions only.

    A second membrane reactor concept is described in chapter 6, the organic-phase is led over an adsorption column in order to adsorb the monoglycerides onto the adsorbate. When the column is saturated with monoesters, the column can be desorbed off-line in a continuous membrane/repeated batch column process. If a 5 % ethanol in hexane solution is used as desorption solvent, monoesters are desorbed selectively leading to a 90 % purity.

    Finally, in chapter 7, the potentials and limitations of the enzymatic esterification are discussed. To predict the steady-state concentration of a continuous reactor, the enzyme kinetics must be described. The membrane reactor is reaction limited, this could be overcome by placing a column packed with immobilized enzyme in the organic phase recirculation loop. Not only esterification can be performed in the pervaporation system, this system could also be suitable for interesterification or transesterification. Then the program TREP should be extended for reactions with different types of fatty acids.

    Infrared spectra of monoacid triglycerides : with some applications to fat analysis
    Ruig, W.G. de - \ 1971
    Wageningen : Pudoc, Centre for Agricultural Publishing and Documentation (Agricultural research reports 759) - 143
    derivaten - alcoholen - glycerol - acylglycerolen - diacylglycerolen - triacylglycerolen - infraroodspectroscopie - analyse - chemie - analytische scheikunde - derivatives - alcohols - glycerol - acylglycerols - diacylglycerols - triacylglycerols - infrared spectroscopy - analysis - chemistry - analytical chemistry
    Increasing potato yield with glyceroltriacetate and glyceroldiacetate
    Kuiper, F. ; Kuiper, P.J.C. ; Aalderen, B.W. van - \ 1969
    Wageningen : Veenman (Mededelingen Landbouwhogeschool Wageningen 69-6) - 7
    plantenvoeding - kunstmeststoffen - mest - solanum tuberosum - aardappelen - plantengroeiregulatoren - derivaten - alcoholen - glycerol - acylglycerolen - diacylglycerolen - triacylglycerolen - plant nutrition - fertilizers - manures - solanum tuberosum - potatoes - plant growth regulators - derivatives - alcohols - glycerol - acylglycerols - diacylglycerols - triacylglycerols
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