Staff Publications

Staff Publications

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

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

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

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

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    Novel surface-active oligofructose fatty acid mono-esters by enzymatic esterification
    Kempen, S.E.H.J. van; Boeriu, C.G. ; Schols, H.A. ; Waard, P. de; Linden, E. van der; Sagis, L.M.C. - \ 2013
    Food Chemistry 138 (2013)2-3. - ISSN 0308-8146 - p. 1884 - 1891.
    lipase-catalyzed synthesis - candida-antarctica lipase - solid-phase synthesis - regioselective acylation - fructose esters - chain-length - disaccharides - inulin - oligosaccharides - ingredients
    This article describes the synthesis of a series of oligofructose monoesters with fatty acids of different chain length (C8, C12, C16 and C18) to obtain food-grade surfactants with a range of amphiphilicity. Reactions were performed in a mixture of DMSO/ButOH (10/90 v/v) at 60 °C and catalysed by immobilised Candida antarctica lipase B. MALDI-TOF-MS analysis showed that the crude reaction products were mixtures of unmodified oligofructose and mostly mono-esters. The conversion into mono-esters increased with the length of the fatty acid chain, reflecting the specificity of the lipase towards more lipophilic substrates. Reverse phase solid phase extraction was used to fractionate the products, which lead to sufficient purity (>93%) of the fatty acid esters for functionality testing. It was shown that derivatives of longer (C16 and C18) fatty acids were more efficient in lowering surface tension and gave a much higher dilatational modulus than derivatives of the shorter (C8 and C12) fatty acids.
    Oligosaccharide synthesis by the hyperthermostable b-glucosidase from Pyrococcus furiosus: kinetics and modelling
    Bruins, M.E. ; Strubel, M. ; Lieshout, J.F.T. van; Janssen, A.E.M. ; Boom, R.M. - \ 2003
    Enzyme and Microbial Technology 33 (2003)1. - ISSN 0141-0229 - p. 3 - 11.
    escherichia-coli - enzymatic-synthesis - bacillus-circulans - hydrolysis - galactosidase - lactose - temperature - disaccharides - glycosidases - glucoamylase
    Oligosaccharides can be synthesised from monosaccharides or disaccharides, using glycosidases as a catalyst. To investigate the potential of this synthesis with beta-glycosidase from Pyrococcus furiosus we determined kinetic parameters for substrate conversion and product formation from cellobiose, lactose, glucose and galactose. The obtained parameters for initial rate measurements of disaccharide conversion were also used for the interpretation of experiments in time. The model for cellobiose gave a good description of the experiments. The enzyme was found to be uncompetitively inhibited by cellobiose and competitively inhibited by glucose. Lactose conversion however, could not be modelled satisfactorily; apparently additional reactions take place. Monosaccharide condensation also yielded oligosaccharides, but much slower. The use of a hyperthermostable, enzyme was found to be positive. More substrate could be dissolved at higher temperatures, which benefited all reactions.
    The production of exopolysaccharides by Lactobacillus delbrueckii subsp. bulgaricus
    Grobben, G. - \ 1998
    Agricultural University. Promotor(en): J.A.M. de Bont; J. Sikkema; M.R. Smith. - S.l. : Grobben - ISBN 9789054858270 - 92
    voeding - disacchariden - nutrition - disaccharides

    Extracellular polysaccharides (EPS) produced by lactic acid bacteria have gained great popularity in the food industry because of their thickening and stabilizing properties. Since lactic acid bacteria have the GRAS ( G enerally R ecognized A s S afe) status, these organisms and their products can be applied as food additives. In particular in the dairy industry, EPS producing lactic acid bacteria are used to improve the texture and viscosity of fermented milk products, like yogurt, viili and långfil and the prevention of syneresis (wheying-off).

    Many lactic acid bacteria producing EPS have already been studied, but since they have numerous medium requirements, including carbohydrates, amino acids, vitamins, purines, pyrimidines and mineral salts, most investigations on the production of EPS were performed using very complex growth media, like milk, whey ultrafiltrate or complex synthetic media. However, these media are often not suitable when the influence of individual medium components on growth and EPS production is studied. Therefore, a chemically defined growth medium is required, containing all components necessary for growth and EPS production.

    In this thesis, the influence of physiological factors and the medium composition on the growth, EPS production and the sugar composition of the EPS produced by Lactobacillus delbrueckii subsp. bulgaricus NCFB 2772 is studied in detail. This lactic acid bacterium is, together with Streptococcus thermophilus , used in the manufacture of yogurt. A chemically defined medium is composed, in which the strain was able to grow and produce EPS. The exopolysaccharides were composed of glucose, galactose and rhamnose in the ratio 1 : 6.8 : 0.7. The EPS production was growth-related, and an excess of carbohydrate did not result in an increased polymer production. It was found that production of EPS was higher with glucose or lactose as the carbohydrate source, than when fructose was used. The amount and composition of the EPS produced on glucose and lactose were identical, the galactose monomer from lactose was not used for growth and polymer production. Limiting amounts of manganese and phosphate in the growth medium resulted in a lower EPS production by Lb. delbrueckii subsp. bulgaricus NCFB 2772. The amount of rhamnose monomer in the EPS was slightly lower than when manganese and phosphate were present in non-limiting concentrations.

    The medium requirements of Lb. delbrueckii subsp. bulgaricus NCFB 2772 were studied using the technique of single and multiple omissions of medium components. Surprisingly, a multiple omission of vitamins from the growth medium caused a significant enhancement of the EPS production. A simplified defined medium was composed, from which many components were omitted which were individually not required for growth. Although the strain grew less well in the simplified medium, the amount of EPS produced was twofold higher than in the complete medium. Furthermore, the EPS production beyond the stationary growth phase was stronger when grown in the simplified medium.

    The influence of the carbohydrate source on the production of EPS and the activities of enzymes involved in the production of sugar nucleotides as precursors for EPS biosynthesis is described. Lb. delbrueckii subsp. bulgaricus NCFB 2772 produced four times more EPS when grown on glucose than when fructose was used and it was found that the EPS produced on fructose contained no rhamnose monomer. Activities of enzymes involved in the synthesis of UDP-glucose, UDP-galactose and dTDP-rhamnose were observed when the strain was grown on glucose. But when grown on fructose, no activities were detected of enzymes leading to the production of dTDP-rhamnose and this may lead to the absence of rhamnose in the EPS produced on fructose. On the other hand, the amount of UDP-glucose and UDP-galactose in extracts of cells grown on fructose and glucose were comparable. Apparently the differences in the amount of EPS produced on glucose and fructose are not caused by the activities of the enzymes leading to the production of these sugar nucleotides.

    Lb. delbrueckii subsp. bulgaricus NCFB 2772 grown on glucose produces two types of EPS concurrently and in almost equal amounts, with molecular weights of 1.7 × 10 6and 4 × 10 4. The exopolysaccharides produced with fructose as the carbohydrate source were composed of mainly a fraction with a low molecular weight of 4 x 10 4. The high- molecular-weight fractions were composed of branched repeating units with glucose, galactose and rhamnose in the ratio 1 : 5 : 1, whereas the low-molecular-weight fractions were more linear and contained glucose, galactose and rhamnose in the ratio 1 : 11 : 0.4. The production of the high-molecular-weight fraction was dependent on the carbohydrate source, whereas the low-molecular-weight fraction was produced more continuously. Since a low amount of rhamnose monomer was found in the EPS produced on fructose, the enzymes involved in the production of dTDP-rhamnose are active, in contrast to the results obtained in Chapter 5, but these activities may be below the detection level of the enzyme assays performed.

    Lb. delbrueckii subsp. bulgaricus NCFB 2772 produces EPS when grown in a defined medium and the amount of EPS is dependent on the carbohydrate source and the presence or absence of several vitamins. For future research, it would be interesting to study the genetics and enzymology of the assembly of the different EPS repeating units in fructose-grown and glucose-grown cells and in cells grown at low optical densities. Furthermore, the mechanisms of the enhanced EPS production as a result of multiple vitamin omissions may be an interesting topic for future research.

    Verwijdering oligosachariden uit reactor verhoogt opbrengst.
    Boon, M.A. ; Janssen, A.E.M. - \ 1998
    Voedingsmiddelentechnologie 25 (1998). - ISSN 0042-7934 - p. 11 - 13.
    oligosacchariden - koolhydraten - opbrengsten - enzymprecursors - kinematica - lactose - disacchariden - oligosaccharides - carbohydrates - yields - enzyme precursors - kinematics - disaccharides
    De enzymatische productie en toepassing van oligosachariden uit lactose. Resultaten van modelberekeningen zijn belicht
    Bepaling van suikers met behulp van HPLC
    Essers, M.L. ; Muuse, B.G. - \ 1983
    Wageningen : RIKILT (Verslag / RIKILT 83.08) - 5
    voedselanalyse - suiker - hplc - disacchariden - monosacchariden - monsters - food analysis - sugar - hplc - disaccharides - monosaccharides - samples
    In dit onderzoek wordt de bruikbaarheid van HPLC voor de bepaling van suikers getest en vergeleken met enzymatische suiker-analyse.
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