Mining microbiota signatures in human intestinal tract metagenomes
Tims, S. - \ 2016
Wageningen University. Promotor(en): Michiel Kleerebezem; Willem de Vos, co-promotor(en): Erwin Zoetendal. - Wageningen : Wageningen University - ISBN 9789462576933 - 264
gastrointestinal microbiota - intestines - genomes - man - hosts - host guest relations - dna microarrays - gastrointestinal diseases - inflammatory bowel diseases - irritable colon - prebiotics - body mass index - oligosaccharides - microbiota van het spijsverteringskanaal - darmen - genomen - mens - gastheren (dieren, mensen, planten) - relaties tussen gastheer en gast - dna microarrays - maagdarmziekten - chronische darmontstekingen - prikkelbaar colon - prebiotica - quetelet index - oligosacchariden
Structure and fermentation of natural and manufactured lactose-based oligosaccharides
Difilippo, E. - \ 2016
Wageningen University. Promotor(en): Harry Gruppen; Henk Schols. - Wageningen : Wageningen University - ISBN 9789462576155 - 128
milks - lactose - oligosaccharides - ingestion - bioactive compounds - isolation - characterization - fermentation - colostrum - food analysis - melksoorten - lactose - oligosacchariden - inname - bioactieve verbindingen - isolatie - karakterisering - fermentatie - colostrum - voedselanalyse
At early stages of life, infant immature intestine is not fully developed, exposing the new-born to potential diseases. Compounds that can exert beneficial actions on the infant intestine are bioactive lactose-based oligosaccharides (LBOs). The natural source of LBOs is mother milk. When human milk is lacking, dietary supplementation with infant formula fortified with manufactured LBOs, such as galacto-oligosaccharides (GOS), is pursued. GOS have been shown to have several properties in common with HMOs. LBOs composition and intestinal fate is extensively described for humans, whereas they are hardly investigated for domestic animal. In this PhD thesis, composition of LBOs in equine and porcine colostrum were described and new structures were elucidated. The analysis were performed mainly using liquid chromatography and capillary electrophoresis techniques. High inter- and intra-individual variation were found for oligosaccharides present in equine and porcine milk. In vivo fermentation fate of porcine milk oligosaccharides (PMOs) was also described analysing PMOs as found in fecal samples of piglets. The results were correlated to existing literature on HMOs. Dietary oligosaccharides are partially present systemically, as suggested from HMO studies. GOS and PMOs in blood, urine and fecal samples from an in vivo feeding trial on piglet were described. Intact dietary oligosaccharides including GOS and milk oligosaccharides from the piglet diet were found in piglet blood and urine samples. All dietary oligosaccharides were fermented/absorbed in vivo, not being detectable in the piglet fecal samples. On the other hand, GOS in vitro fermentation by piglet inoculum delineate a unique fermentation profile regarding GOS size consumption compared to GOS in vitro fermentation by human fecal inoculum. Similar degradation profile regarding GOS linkage types was observed for GOS fermentation by piglet and human inocula.
Effect of fructooligosaccharides on gut health in neonatal piglets : VDI-3 Piglet experimen
Schokker, D. ; Jansen, R. ; Jansman, A.J.M. ; Vastenbouw, S. ; Bree, F.M. de; Bossers, A. ; Rebel, J.M.J. ; Smits, M.A. - \ 2015
Wageningen : Wageningen UR Livestock Research (Livestock Research report 913) - 39
piglets - intestines - animal health - oligosaccharides - intestinal microorganisms - immunology - biggen - darmen - diergezondheid - oligosacchariden - darmmicro-organismen - immunologie
Gut microbial colonization and immune competence development are affected by early-life environmental and dietary interventions. The interplay between microbiota in the intestinal tract and the gut mucosal surfaces of the host is critical for the development of an accurate immune competence. In the present study we intervened during early life of suckling piglets by a daily oral administration of fructooligosaccharides (FOS solution) from day 2 – 14 and investigated the effects on intestinal microbiota composition (by 16S rDNA sequencing) and biological processes of the intestinal mucosal tissue (by genome-wide intestinal gene expression analysis) during the suckling phase.
Characterization of sugar beet pulp derived oligosaccharides
Leijdekkers, M. - \ 2015
Wageningen University. Promotor(en): Harry Gruppen; Henk Schols. - Wageningen : Wageningen University - ISBN 9789462572430 - 162
suikerbieten - bietenpulp - oligosacchariden - versuikering - bioraffinage - voer - fermentatie - sugarbeet - beet pulp - oligosaccharides - saccharification - biorefinery - feeds - fermentation
This thesis aimed at characterizing complex mixtures of sugar beet pulp derived oligosaccharides, in order to be able to monitor and optimize the enzymatic saccharification of sugar beet pulp.
Hydrophilic interaction chromatography with on-line evaporative light scattering detection and multidimensional mass spectrometry (HILIC-ELSD-MSn) was developed as a versatile technique for the characterization of a wide range of neutral and acidic plant cell wall derived oligosaccharides. It was shown that the separation capacity of HILIC for acidic oligosaccharides outperforms other techniques. HILIC-MSn enabled efficient sequence elucidation of oligosaccharides in complex mixtures.
The enzymatic saccharification of sugar beet pulp was optimized to release the maximum amounts of monomeric galacturonic acid and arabinose with limited concomitant degradation of cellulose, using conditions that are feasible for industrial upscaling. The oligosaccharides that were obtained after hydrolysis were characterized, thereby enabling recognition of enzyme activities additionally needed for the full degradation of recalcitrant oligosaccharides.
The in vitro fermentation characteristics of sugar beet pectic oligosaccharides (SBPOS) were studied using human and pig fecal inocula. The fate of the different classes of SBPOS, the production of short-chain fatty acids and the changes in human fecal bacterial populations during in vitro fermentation were described. Several modifications in the microbiota composition that are potentially beneficial to host health were observed.
HILIC was also coupled to traveling-wave ion mobility mass spectrometry to enable the simultaneous separation and characterization of complex mixtures of various isomeric pectic oligosaccharides. The developed method was used to characterize isomeric sugar beet rhamnogalacturonan I derived oligosaccharides carrying a glucuronic acid substituent, thereby identifying novel structural features of sugar beet pectin.
Galacto-oligosaccharides to counter the side effects of antibiotic treatments
Ladirat, S.E. - \ 2014
Wageningen University. Promotor(en): Harry Gruppen; Henk Schols. - Wageningen : Wageningen University - ISBN 9789461738394 - 160
oligosacchariden - darmmicro-organismen - bifidobacterium longum - antibiotica - prebiotica - amoxicilline - oligosaccharides - intestinal microorganisms - bifidobacterium longum - antibiotics - prebiotics - amoxicillin
Antibiotic treatments are known to disturb the composition and metabolic activity of the human gut microbiota and, therefore, may lead to gut disorders. In this thesis, it was investigated whether and by which mechanisms galacto-oligosaccharides (GOS), a prebiotic known to stimulate the growth of bifidobacteria and to positively influence human health, may counter the negative effects of antibiotics on the microbiota.
First, a high throughput approach combining the in vitro fermentation screening platform with a phylogenetic microarray read-outs was shown to be reliable to simultaneously analyse the effects of several often-used antibiotics on the intestinal microbiota. Then, using the same approach, the recovery of the composition and metabolic activity of the microbiota treated with four selected antibiotics upon GOS addition was shown to be antibiotic and dose dependant. The addition of GOS to an amoxicillin (AMX)-treated microbiota was considered successful as, after a decrease of the levelofBifidobacterium species, the recovery of mainly Bifidobacterium longum, was observed. The growth of bifidobacteria and the production of the beneficial butyrate tended to be higher upon addition of small GOS (dimers-trimers) than upon large GOS in non-treated microbiota (tetramers to hexamers). On the contrary in AMX-treated microbiota, the growth of bifidobacteria and production of butyrate tented to be higher upon addition of large GOS than upon addition of small GOS. The positive results of GOS on AMX-treated microbiota during in vitro experiments were evidenced in a double-blind randomized parallel intervention study involving 12 healthy adults.
Overall, the addition of GOS, especially the large oligosaccharides, allowed the recovery of B. longum and, subsequently, stimulated the activity of the microbiota through cross-feeding after an AMX treatment.
Synthesis of galacto-oligosaccharides with ß-galactosidases
Warmerdam, A. - \ 2013
Wageningen University. Promotor(en): Remko Boom, co-promotor(en): Anja Janssen. - S.l. : s.n. - ISBN 9789461735621 - 171
oligosacchariden - bèta-galactosidase - productie - synthese - immobilisatie - bioreactoren - lactose - oligosaccharides - beta-galactosidase - production - synthesis - immobilization - bioreactors - lactose
Galacto-oligosaccharides (GOS) are generally enzymatically synthesized with β-galactosidases. GOS are of interest because of their prebiotic effects on human health. They are mainly applied in infant nutrition, because of their resemblance to human milk oligosaccharides, but they are also applied in e.g. dairy products and beverages.
β-Galactosidases synthesize GOS from lactose through transgalactosylation: instead of only using water as acceptor (as in hydrolysis), they can use carbohydrates as acceptor. In this way, GOS with a degree of polymerization up to ten can be formed. The ratio of hydrolysis over transgalactosylation depends on the substrate concentration, temperature, and the source of the enzyme.
A β-galactosidase preparation from Bacillus circulans, called Biolacta N5, is known to produce high GOS yields compared to enzymes from other sources. The aim of this thesis was to obtain more insight on the mechanism of GOS production with Biolacta N5 and to investigate how the GOS production process can be optimized.
Biolacta N5 consists of four β-galactosidase isoforms, β-gal-A, β-gal-B, β-gal-C, and β-gal-D, which were purified and characterized in chapter 2. At low substrate concentrations, these isoforms differ in hydrolysis and transgalactosylation activity. β-Gal-D seems the best isoform for GOS production, followed by β-gal-C and β-gal-B, and β-gal-A showed the least GOS formation. By studying the thermodynamics of lactose conversion with isothermal titration calorimetry (ITC), the differences in behavior were confirmed, although the interpretation of the results of ITC was quite difficult dealing with a complex mixture of reactions. In contrast to the selectivity at low substrate concentrations, the selectivity of the isoforms hardly differed at high lactose concentrations. These conditions are usually used for industrial GOS production. Only β-gal-A produced slightly more galactose. The initial GOS formation rates indicated that β-gal-A and β-gal-B are the best isoforms for GOS production.
In chapter 3, the effect of high concentrations was further studied on the behavior of the complete Biolacta N5 preparation. High concentrations of reacting and non-reacting carbohydrates were added to the oNPG activity assay with Biolacta N5. Small carbohydrates were found to act as acceptor in the reaction, which resulted in an increased reaction rate. The rate of the limiting step of the reaction, i.e. the binding of the galactose residue with the acceptor, is increased, and therewith the release of the product is faster. At the same time, the additives cause molecular crowding, which results in a higher affinity between the enzyme and the substrate.
In chapter 4, a kinetic model was developed to quantify the effects of lactose, glucose, galactose, and oligosaccharides on the oNPG converting activity of the β-galactosidases from B.circulans, Aspergillus oryzae and Kluyveromyces lactis. Using multiple substrates simultaneously yields more information than using only lactose or oNPG, because of the competition between the substrates. Three main differences were found that explain why Biolacta N5 produces higher GOS yields than other β-galactosidases: (i) it had a higher reaction rate constant of using lactose or oligosaccharides as substrate relative to water as acceptor (so it had a very low relative hydrolysis rate); and (ii) it also had a high reaction rate with galactose as acceptor, whereas (iii) the other two enzymes are strongly inhibited by galactose. The reaction rate constants indicate that β-gal-A is the most active isoforms in GOS production; however, also its hydrolysis rate is highest. Many of the rate constants increase with increasing molecular weight of the isoforms.
Chapter 5 reports on the stability of Biolacta N5 at various temperatures in buffer, and in systems with initially 5.0 and 30% (w/w) lactose. Samples were taken in time and analyzed for oNPG converting activity. The oNPG converting activity was corrected for the presence of lactose, glucose, galactose, and oligosaccharides with the mechanistic model from chapter 4. The stability, expressed with the half-life time, of the enzyme was found to strongly increase with initial lactose concentrations. At high substrate concentration, higher temperatures can be used for GOS production than was presumed feasible based on stability measurements in diluted solutions.
Biolacta N5 is still active after one batch run of GOS production, but in a batch process the enzyme is wasted after the reaction. For this reason, the use of immobilized enzyme in a continuous packed bed reactor (PBR) was investigated in terms of productivity in chapter 6. The carbohydrate composition of the product in both systems was comparable. The half-life time of the immobilized enzyme at a lactose concentration of 33% (w/w) and 50ºC was approximately 90 days. The enzymatic productivity using immobilized enzyme in a PBR may be six times higher than that using free enzyme in a batch reactor. When striving for an equal volumetric productivity of both systems, the volume of a PBR can be much smaller than that of a batch reactor, depending on the enzyme dosage and running time of the one batch.
Chapter 7 discusses various alternatives for process optimization. One option for a higher GOS productivity is to use an enzyme preparation that contains only β-gal-A and β-gal-B. A somewhat higher oligosaccharide yield can be obtained when initially using a mixture of lactose with a better acceptor molecule. This results in a changed oligosaccharide composition and less lactose in the final product. The sustainability of GOS production in a PBR with immobilized enzyme and 33% (w/w) lactose seems to be similar in terms of exergy to that in a batch reactor with free enzyme and 60% (w/w) lactose.
Gastrointestinal-active oligosaccharides from human milk and functional foods
Albrecht, S.A. - \ 2011
Wageningen University. Promotor(en): Harry Gruppen; Fons Voragen, co-promotor(en): Henk Schols. - [S.l.] : S.n. - ISBN 9789085859871 - 200
oligosacchariden - moedermelk - spijsverteringskanaal - zuigelingen - borstvoeding - koolhydraatmetabolisme - oligosaccharides - human milk - digestive tract - infants - breast feeding - carbohydrate metabolism
Keywords: human milk oligosaccharides (HMOs), galacto-oligosaccharides (GOS), konjac glucomannan (KGM), breast milk, baby feces, gastrointestinal metabolization, blood-group specific conjugates, CE-LIF-MSn
Oligosaccharides, as present in human milk or supplemented to food, are renowned for their biological activity in the gastrointestinal tract. So far, little is known about the implication of oligosaccharide structures on their gastrointestinal fate. The influence of diet-related oligosaccharides on the postnatal gastrointestinal development and on the establishment of a balanced microflora is of special interest. Therefore, the present research aimed at an advanced understanding of the gastrointestinal metabolization of diet-related oligosaccharides, focusing on infant nutrition.
Capillary electrophoresis with laser-induced fluorescence detection (CE-LIF) was introduced as a sensitive, qualitative and quantitative method for the analysis of individual galactooligosaccharides (GOS) from complex food matrices. The method also showed to be useful for the monitoring and characterization of complex konjac glucomannan (KGM) oligosaccharides, resulting from enzymatic digestion of the KGM polysaccharide andin vitro fermentation with human gut flora. The analysis and identification of human milk oligosaccharides (HMOs) in breast milk and the characterization of oligosaccharides as present in the feces of breast-, formula- and mixed-fed babies was performed by CE-LIF coupled to a mass spectrometer (CE-LIF-MSn). The type of feeding determines the presence of diet-related oligosaccharides in baby feces. For breast-fed babies a gradual change in fecal oligosaccharide profile was found during the first six months postpartum. Three continuous stages of fecal oligosaccharide profiles were defined, comprising the presence of the genetically determined HMO-profile of the breast milk consumed (stage 1), the presence of HMO-units conjugated to blood group determinants from gastrointestinal mucins (stage 2) and predominantly oligosaccharides characteristic for follow-up feeding when solid food is introduced (stage 3). In total, sixteen fecal oligosaccharides, which pointed to the degradation and gastrointestinal metabolization of diet-related oligosaccharides and which were not present in human milk or infant formula, were identified in this research.
Monitoring the gastrointestinal fate of diet-related oligosaccharides pointed to an individual-dependent gastrointestinal adaptation to enteral food during the postnatal period.
Enzymatic production of hyaluronan oligo- and polysaccharides
Kooy, F.K. - \ 2010
Wageningen University. Promotor(en): Gerrit Eggink; Hans Tramper, co-promotor(en): Carmen Boeriu. - [S.l. : S.n. - ISBN 9789085856481 - 174
hyaluronzuur - derivaten - oligosacchariden - polysacchariden - industriële microbiologie - industriële enzymen - hyaluronic acid - derivatives - oligosaccharides - polysaccharides - industrial microbiology - industrial enzymes
Hyaluronan oligo- and polysaccharides are abundant in the human body. Depending on the chain length, hyaluronan is an important structural component or is involved in influencing cell responses during embryonic development, healing processes, inflammation and cancer. Due to these diverse roles of hyaluronan, there are multiple applications already in use or in development, such as supplementation of fluid in eyes and joints, cosmetic tissue augmentation, enhancing wound healing, tissue engineering, cancer treatment, controlled drug release and targeted drug delivery. State-of-the-art hyaluronan production techniques include bacterial fermentation to produce long hyaluronan polymers with a small chain length distribution and in vitro enzymatic systems to produce hyaluronan oligosaccharides of one chain length. Both production strategies make use of hyaluronan synthase (HAS), an enzyme that elongates UDP-glucuronic acid (UDP-GlcUA) and UDP-N-acetylglucosamine (UDP-GlcNAc) into hyaluronan.
The main question in hyaluronan production today is how the chain length of the products can be controlled. Since most production processes use hyaluronan synthases, the aim of this thesis was to elucidate the polymerization mechanism of Pasteurella multocida hyaluronan synthase (PmHAS) from a biochemical point of view. In addition, the acquired knowledge is used for improving the control on hyaluronan chain length in polymerization reactions using PmHAS. Valuable information important for production processes on the intrinsic properties of the enzyme, such as substrate affinity, can be obtained by kinetic studies using single-step elongations. Kinetic studies also provide insights on how polymerization is achieved and, combined with structural studies, the identification of amino acid residues that are important for polymerization. This knowledge can be used for improving the hyaluronan synthesis performance of the enzyme.
Kinetic studies require purified substrates in quantities of mg-scale. Hyaluronan (HA) oligosaccharides were obtained through stepwise hyaluronan cleavage using hyaluronidase and consecutive separation of the reaction mixture by flash-chromatography (Chapter 2). The enzymatic hydrolysis was optimized by experimental design studies with pH, enzyme concentration and reaction time as parameters. Empirical models were developed for the yield of each individual target HA oligosaccharide using the results from a central composite design. Selective production of short HA oligomers (HA ≤ 10) or longer oligosaccharides (HA > 10) was made possible through implementation of the reaction conditions indicated by the empirical models. Separated HA oligomers were characterized by a combination of anion exchange chromatography and matrix-assisted laser desorption/ionization mass spectrometry with time-off-flight analysis. Using these techniques, the desired quantities of purified target HA oligosaccharides (n = 4, 6, 8 and 10) were obtained and used in further studies.
Besides the single-step elongations assessed in kinetic studies, full polymerization studies with both UDP-sugars available were used to investigate the influence of substrate concentrations on the chain length distribution of the hyaluronan products. In order to quantify all oligosaccharides formed during PmHAS polymerization in μl-scale reactions, HA templates consisting of a fluorophore-labeled HA tetrasaccharide (HA4) were generated (Chapter 3). A fast, simple and sensitive assay was developed based on fluorophore-assisted carbohydrate electrophoresis (FACE) that was used for quantification and characterization of PmHAS polymerization products.
The individual β1,3-glucuronyl-transferase (UA-transferase) and β1,4-N-acetylglucosamine-transferase (NAc-transferase) activities of PmHAS were investigated separately using kinetic studies, where the reaction of an HA oligosaccharide was followed with, respectively, UDP-GlcUA or UDP-GlcNAc in single-step elongations. In Chapter 4, the influence of HA oligosaccharide length (n = 4, 5, 6, 7, 8 and 9) on the polymerization reaction was investigated by one-substrate kinetics, varying only the HA oligosaccharide concentration at saturating UDP-sugar concentration. These reactions followed Michaelis Menten kinetics, although HA oligosaccharides may become inhibiting at elevated concentrations above 6 mM. The observed kcat values increased with increasing HA oligosaccharide length to a constant value at HA6 and HA7. The specificity constant kcat/Km values for HA oligosaccharides in the UA-transferase domain increased at increasing oligosaccharide length, whereas in the NAc-transferase domain kcat/Km values were constant at a low value. This indicates that there are two separate oligosaccharide binding sites of different lengths, one in each transferase domain of PmHAS. In Chapter 4, it was demonstrated that the chain-lenght distribution in PmHAS polymerization reactions can be decreased, and thus improved, by using saturating concentrations of both HA oligosaccharides and UDP-sugars.
Chapter 5 describes two-substrate kinetic studies, where in single-step elongations both HA oligosaccharide and one of the UDP-sugars were varied, to investigate the polymerization mechanism of each individual transferase domain in PmHAS. Dead-end inhibition studies and goodness-of-fit parameters were used to distinguish between two-substrate models. From this analysis follows that both transferase domains elongate the UDP-sugar through a sequential mechanism, which is most likely an ordered one. In this proposed mechanism, the UDP-sugar is first bound followed by binding of the HA oligosaccharide, after which first the elongated HA oligosaccharide and then UDP is released. Large differences between Km values for UDP-GlcNAc and UDP-GlcUA, also found in Class I HAS enzymes, suggest that UDP-GlcNAc concentration is involved in the regulation of HAS activity and thus the chain length of hyaluronan products.
Structural studies were used to evaluate the results obtained with kinetic studies. In Chapter 4, a structural homology model of PmHAS was built based on crystal structure K4CP chondroitin polymerase in E. coli, which has a high sequence identity of 62% and high sequence homology of 78% with PmHAS. The active sites of PmHAS are structurally related to other glycosyltransferases and this provided information on where the oligosaccharide binding sites could be located. These putative oligosaccharide binding sites differ in size, as was predicted by kinetic studies (Chapter 4). Furthermore, structural similarities between PmHAS, α1,3-galactosyltransferase (α3GT) and β1,4-galactosyltransferase (β4Gal-T1) demonstrated that PmHAS contains in each transferase domain one flexible loop that forms a bridge over the active site. In crystal structures of α3GT and β4Gal-T1, these flexible loops have been shown to change conformation upon binding the UDP-sugar. Based on similarities in kinetic mechanisms and structures between PmHAS, α3GT and β4Gal-T1, it is likely that the flexible loops in PmHAS follow a similar conformational change, which makes the proposed ordered mechanism the only possible mechanism (Chapter 5).
In Chapter 6, the knowledge on the PmHAS polymerization mechanism gained in earlier chapters is reviewed and used to create new insights in the polymerization mechanism of Class I HAS enzymes. Both Class I HASs and PmHAS are used in hyaluronan production, and, therefore, the differences and similarities are discussed in Chapter 6. During hyaluronan production, there are many different aspects, such as intrinsic properties of the enzyme, cell metabolism and fermentation reaction conditions, that influence hyaluronan chain length and yield (Chapter 6). Moreover, hyaluronan production systems that are able to produce hyaluronan of desired length are discussed in Chapter 6 and a personal view of how these systems can be improved is presented.
Transcriptome analysis of the challenged gut barrier in rats : mucosal response to Salmonella and Fructo-oligosaccharides
Rodenburg, G.C.H. - \ 2008
Wageningen University. Promotor(en): M.B. Katan, co-promotor(en): Jaap Keijer; I.M.J. Bovee-Oudenhoven. - [S.l.] : S.n. - ISBN 9789085048701 - 183
darmslijmvlies - stressreactie - salmonella - fructanen - oligosacchariden - genexpressie - ratten - transcriptomics - intestinal mucosa - stress response - salmonella - fructans - oligosaccharides - gene expression - rats - transcriptomics
De darmbarrière is een complex systeem dat het lichaam beschermt tegen schadelijke stoffen en pathogenen die met het voedsel binnenkomen. Om beter inzicht te krijgen in de biologische processen die zorgen voor de barrièrefunctie van darmcellen hebben we in een levend organisme, de rat, bestudeerd hoe deze reageren op twee verschillende stoffen die stress van de darmbarrière veroorzaken: het veel voorkomende voedselpathogeen Salmonella en het voedingsmiddel Fructo-oligosaccharides (FOS). Dit hebben we gedaan met zogenaamde whole genome transcriptoom (genexpressie) analyse, waarmee de activiteit van nagenoeg alle genen tegelijkertijd kwantitatief bepaald kan worden. Ons onderzoek is een van de eerste studies die de moleculaire effecten van een Salmonella infectie op darmcellen van een levend dier heeft onderzocht. Het bleek, tegen de verwachting in, dat Salmonella niet alleen een effect heeft op dunne darm cellen, maar ook op dikke darm cellen. Verder hebben we gevonden dat celkweek modellen, die tot nu toe veel gebruikt zijn voor infectieonderzoek , slechts in zeer geringe mate voorspellend zijn voor de effecten in het dier. Met de genexpressie analyse hebben we niet alleen nieuwe darmbarrière processen gevonden, maar ook nieuwe mogelijke biomarkers die gebruikt kunnen worden om de darmgezondheid te meten in interventie proeven met mensen of dieren. Een voeding met FOS verhoogt de doorlaatbaarheid van de darmwand en verergert de infectie met Salmonella. Dit ging gepaard met verhoogde expressie van genen die betrokken zijn bij de weerstand of afweer. Dit betekent dat verhoging van deze weerstand markers voorzichtig geïnterpreteerd moet worden en niet per definitie een gunstige situatie (verhoogde weerstand) weerspiegelt. Het heeft de voorkeur om weerstand markers altijd te koppelen aan meetbare en eenduidige eindpunten zoals passage van de bacteriën door de darmwand. Tenslotte hebben we sterke aanwijzingen verkregen dat een ontregeld energie metabolisme in darmcellen de onderliggende oorzaak is van de verhoogde doorlaatbaarheid van de darmwand en verminderde weerstand door FOS consumptie. Ons onderzoek heeft vele nieuwe inzichten opgeleverd in mechanismen die een rol spelen in de barrière functie van de darm en vormt de basis voor verder onderzoek naar voedingsmiddelen die de darmbarrière kunnen versterken.
Galactosyl hydrolases from Bifidobacterium adolescentis and Bifidobacterium longum
Hinz, S.W.A. - \ 2005
Wageningen University. Promotor(en): Fons Voragen, co-promotor(en): Jean-Paul Vincken. - Wageningen : Wageningen University - ISBN 9789085041832 - 133
galactosidasen - bifidobacterium adolescentis - bifidobacterium longum - galactanen - oligosacchariden - galactosidases - bifidobacterium adolescentis - bifidobacterium longum - galactans - oligosaccharides
The human intestine contains many bacteria, among which bifidobacteria. These can have a positive effect on human health. By consuming products containing dietary fibres (prebiotics), the amount of these intestinal bacteria can be stimulated, because they contain enzymes, which are able to degrade the fibres. Knowing which enzymes are present in the bacteria, will help to determine which kind of dietary fibres are suitable for use as a prebiotic. In this research, enzymes present in bifidobacteria, which were able to degrade the fibres galactan and galacto-oligosaccharides, were investigated. Three different enzymes were examined: a beta-galactosidase, an endo-galactanase, and an alpha-galactosidase. The results of this thesis gave more insight in how galactans and galacto-oligosaccharides can be degraded by bifidobacteria.
Glycosyl hydrolases from Bifidobacterium adolescentis DSM20083 : Their role in the metabolism and synthesis of oligosaccharides.
Broek, L.A.M. van den - \ 2005
Wageningen University. Promotor(en): Fons Voragen. - Wageningen : WUR - ISBN 9789085041436 - 188
bifidobacterium adolescentis - hydrolasen - glycosidasen - oligosacchariden - synthese - bifidobacterium adolescentis - hydrolases - glycosidases - oligosaccharides - synthesis
Nowadays, there is an increasing interest for food, which is health beneficial for humans. Prebiotics e.g. is used to stimulate the growth of bacteria in the gut that have a positive effect on human health. It is claimed that bifidobacteria in the colon improve health and well being of humans. The first aim of this study was to identify and characterize enzymes from Bifidobacterium adolescentis, which can degrade non-digestible oligosaccharides. To make an inventory what kind of enzymes are present it can be predicted what kind of oligosaccharides can stimulate the growth of bifidobacteria. The second aim was to synthesize new oligosaccharides by the characterized enzymes to produce new sugars, which can be used as preferentially prebiotics for Bifidobacterium adolescentis. Different enzymes were cloned and characterized and most of the enzymes were able to produce new oligosaccharides.
Prebiotics and probiotics in infant nutrition
Bakker-Zierikzee, A. - \ 2005
Wageningen University. Promotor(en): Frans Kok; J.G. Bindels. - - 148
zuigelingenvoeding - flesvoedingsamenstelling - probiotica - melkzuurbacteriën - darmmicro-organismen - oligosacchariden - infant nutrition - infant formulae - probiotics - lactic acid bacteria - intestinal microorganisms - oligosaccharides
IntroductionIn general breast-fed infants suffer less from infection, which could be partly explained by the specificcompostionand metabolic activity of their intestinalmicroflora. During the last two decades, many attempts have been made to mimic the intestinal flora of breast fed infants in formula fed infants. Bothprebioticsandprobioticsbased concepts have been developed to beneficially change the intestinalmicrofloraand thus induce positive health effects. We conducted two infant nutrition studies with the objective to compare the effects of infant formulas containing eitherprebioticsorprobioticsin infants on the composition (%bifidobacteriaand lactobacilli) and metabolic activity (short chain fatty acid profile, lactate concentration and pH) of the intestinalmicrofloraand on Indicators of development of thesecretoryimmune response (faecalSlgAconcentration).Study designIn both studies, infants were enrolled within 3 days after delivery and followed during the first 32 weeks of life. Except for the intervention, the design of both studies was identical. Infants of whom the mothers decided not to breast-feed, were at random and double blindly allocated to one of the formula groups. A group of breast-fed infants was included as a reference. The first study, included 63 infants that were breast fed, 19 fedaregular, non-supplemented infant formula, 19 received infant formula containing a mixture of 0.6 g/100ml GOS (90%) and FOS (10%), 19 received standard formula containing 6.0x109 /100ml viableBifidobacteriumanimalis strain Bb-12. The second study included 38 infants on breast milk, 17 on standard,unsupplementedformula and 17 on formula containing 0.6 g/100ml GOS. During intervention, parents were asked to take faeces samples from the diaper of their infants on postnatal day 5, 10, 28 and once every 4 weeksthereafter.ResultsThe GOS/FOS-, GOS-, Bb-12 formula aUinduced an intestinalmicrofloradominated bybifidobacteria(59.2%7.7%, 76.5:1:2.6% and 69.7:1:2.7%mean:l:SEMresp. at 16w) and no significant differences were found compared to the standard formula group (56:1:6.4%). In contrast, we did show a significant effect of GOS/FOS on the percentage of lactobacilli (6:1:2.6% at 12w, p=0.OO7) compared to the standard formula group (1:1:0.4%), whereas no significant effect was found for the GOS- and Bb-12 formula (1:1:0.4% and 2.4:1:1.7%resp. at 12w).Infants fed on GOS/FOS formula showed a metabolic activity of the flora comparable to that of breast fed infants. GOS/FOS formula induced a faecal SCFA profile (acetate/propionate/ butyrate/others) comparable to that found in breast fed infants (82/14/2/2% vs. 90/6/2/2% at 16w), whilethat of GOS- and Bb-12 fed infants is more like that in standard formula fed infants (78/16/3/2 and 70/22/6/3 vs. 73/20/5/3 at age 16w). We also demonstrated that the faecal lactate concentration of the GOS/FOS group was comparable to breast fed infants (40.9:1:10.7 vs. 45.2%9.0mmollactate/kg faeces), whereas that of GOS- and Bb-12 fed infants was more like standard formula fed infants (12.2:1:5.1 and 6.1 :1:4.2 vs. 0.8:1:0.7). Also the faecal pH of the GOS/FOS group was highly comparable to that in breast-fed infants (5.6:1:0.2 vs. 5.7:1:0.3), whereas that of GOS- and Bb-12 fed infants was more comparable to that of standard formula fed infants (pH 6.5:1:0.3 and 6.6:1:0.2 vs. 7.1:1:0.2).Finally we showed that the GOS/FOS formula group showed a marked trend towards higher faecalSigAlevels compared to the standard formula group (0.84 (0.6-1.8) vs. 0.39 (0.1-0.9), median (P25-P75), p=0.015 at age 16w), which could not be demonstrated in the GOS and Bb-12 infant formula groups.CondusionAlthough, more research is needed to elucidate the effects of GOS/FOS formula on hard clinical endpoints, based on our findings it can bereasonably assumed that infants fed onGOS/FOSwill have a healthbenefit compared to infants fed on standard infant
Oligosaccharide production with thermophilic enzymes
Bruins, M.E. - \ 2003
Wageningen University. Promotor(en): Remko Boom, co-promotor(en): Anja Janssen. - [S.I.] : S.n. - ISBN 9789058088406 - 119
oligosacchariden - productie - thermofiele micro-organismen - glycosidasen - voedselverwerking - oligosaccharides - production - thermophilic microorganisms - glycosidases - food processing
The goal of the research reported in this thesis was to develop a process concept for the tailor made production of oligosaccharides. These specific non-digestible oligosaccharides can be used as prebiotics. They promote the growth of beneficial bacteria in the gastrointestinal (GI) tract. Commercial prebiotic oligosaccharides are often not pure oligosaccharides, but mixtures. In this thesis focus is on the production of oligosaccharides of higher purity.
Our main interest was in a production process at elevated temperatures. This can have many advantages, amongst which is the possibility to increase the substrate concentration. We used a thermophilicβ-glycosidase from Pyrococcus furiosus . Enzymes from thermophilic microorganisms have unique characteristics such as high temperature-, chemical- and pH stability. Applications with thermophilic enzymes are summarised in chapter 2. The main advantages of performing processes at higher temperatures are the reduced risk of microbial contamination, lower viscosity, improved transfer rates and improved solubility of substrates. However, co-factors, substrates or products might be unstable or other side reactions may occur.
One route of oligosaccharide production is the synthesis from monosaccharides or disaccharides, using glycosidases as a catalyst. Monosaccharides can be condensated to disaccharides and disaccharides can be transglycosylated to trisaccharides. To investigate the potential of this synthesis withβ-glycosidase fromPyrococcus 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. This research is described in chapter 3.
Besides the advantage of higher substrate solubility, temperature also influences enzyme kinetics. In chapter 4, the thermostable Pyrococcus furiosus-glycosidase was applied for oligosaccharide production from lactosein a kinetically controlled reaction. The experiments showed that higher temperatures are beneficial for the absolute as well as relative oligosaccharide yield.
However, at reaction temperatures of 80°C and higher, the inactivation rate of the enzyme in the presence of sugars was increased by a factor 2, compared to the inactivation rate in the absence of sugars. This increased enzyme inactivation was caused by the occurrence of Maillard reactions between the sugar and the enzyme. The browning of our reaction mixture due to Maillard reactions was modelled by a cascade of a 0 thand 1 storder reaction and related to enzyme inactivation. From these results we conclude that modification of only a small number of amino-groups already gives complete inactivation of the enzyme.
Reduction of Maillard reactions can be done by altering process conditions or through modification of the enzyme, either chemically or by altering the enzyme structure through genetic modifications. Chemical modification of the enzyme was studied. The enzyme was covalently immobilised on Eupergit. Unfortunately, the immobilisation did not reduce Maillard reactivity.
Further reaction optimisation required a down-stream processing method for oligosaccharide separation. This was also essential for the production of a pure oligosaccharide product. Two methods for oligosaccharide purification are described in chapter 5.
Oligosaccharides were produced in a condensation reaction using the -glycosidase from Pyrococcus furiosus. With a 60% (w/w) galactose solution as the substrate and oligosaccharide yield of 18% (w/w) was obtained. The feasibility of a Simulated Moving Bed (SMB) for downstream separation was investigated by modelling. The required parameters were determined experimentally with column experiments. The components could be separated with an SMB into a 91% pure product stream and a 99% pure galactose stream. This galactose stream can be recycled to the enzyme reactor. Also nanofiltration can be used for oligosaccharide purification. This system was also modelled and the results were compared to those that can be achieved with SMB.
It is also possible to produce transgalacto-oligosaccharides in a more conventional way, with lactose as a substrate. Production is much cheaper when compared to a galactose-based process. Separation of oligosaccharides from this reaction via SMB was also studied.
The size of all separation units is still considerably large and further optimisation is necessary to make a process for the production of specific high purity galacto-oligosaccharides cost-effective.
Various aspects of the process are discussed further in chapter 6. Emphasis is on the specific influence of temperature on the process and on further optimisation of the downstream processing of oligosaccharides.
Intibo als alternatief voor amgb's bij gespeende biggen
Krimpen, M.M. van; Binnendijk, G.P. ; Plagge, J.G. ; Prado, C. del - \ 2002
Lelystad : Praktijkonderzoek Veehouderij (Praktijkboek / Praktijkonderzoek Veehouderij 2) - 31
biggen - postspeeninterval - inuline - fructanen - oligosacchariden - medicinale planten - antimicrobe-eigenschappen - medicinaal voer - groeibevorderaars - voedertoevoegingen - varkenshouderij - dierlijke productie - prestatieniveau - varkensvoeding - alternatieve methoden - piglets - postweaning interval - inulin - fructans - oligosaccharides - medicinal plants - antimicrobial properties - medicated feeds - growth promoters - feed additives - pig farming - animal production - performance - pig feeding - alternative methods
Het gebruik van antimicrobiële groeibevorderaars (AMGB's) staat ter discussie en wordt in de toekomst mogelijk verboden. Met het vooruitzicht hierop is de mengvoersector bezig met het ontwikkelen van voerconcepten die een alternatief moeten zijn voor AMGB's. :Op verzoek van Speerstra Feed Ingredients BV te Lemmer heeft het Praktijkonderzoek Veehouderij een onderzoek uitgevoerd naar de effectiviteit van Intiboe, een fructooligosaccharide, als alternatief voor AMGB. :In het onderzoek zijn twee experimenten uitgevoerd, met elk drie proefbehandelingen (een positieve en negatieve controle en de behandeling met Intiboe). In beide experimenten werd een dosering van 300 gram/ton werkzame stof Intiboe toegepast. In experiment I werd een verdund (10 %-tig) mengsel (Intiboe 9-10) verwerkt en in experiment II een onverdund product (Intiboe9). Op een leeftijd van gemiddeld 4 weken zijn de biggen gespeend en ingedeeld voor de proef. Zij zijn vanaf spenen 34 dagen gevolgd. In beide experimenten zijn circa 540 biggen gevolgd. Per behandeling zijn 18 herhalingen uitgevoerd.
Characterisation of complex xylo-oligosaccharides from xylan rich by-products
Kabel, M.A. - \ 2002
Wageningen University. Promotor(en): A.G.J. Voragen; H.A. Schols. - S.l. : S.n. - ISBN 9789058086969 - 128
xylaan - oligosacchariden - hydrolysaten - karakterisering - bijproducten - hout - eucalyptus - tarwezemelen - maïsspillen - brouwgranen - gerst - verteerbaarheid - chromatografie - massaspectrometrie - kernmagnetische resonantiespectroscopie - xylan - oligosaccharides - hydrolysates - characterization - byproducts - wood - eucalyptus - wheat bran - maize cobs - brewers' grains - barley - digestibility - chromatography - mass spectrometry - nuclear magnetic resonance spectroscopy
Hydrolysates obtained by hydrothermal treatment of four xylan rich by-products (wheat bran, brewery's spent grain, corn cobs and Eucalyptus wood) were characterised. Depending on the feedstock material studied, the xylan originally present differed in substitution with arabinose, 4- O -methylglucuronic acid and O -acetyl substituents. Due to a partial release of the various substituents and depolymerisation of the xylan by the hydrothermal treatments performed, a wide variety of differently substituted XOS and xylan-fragments were obtained.
High performance anion-exchange chromatography (HPAEC), reversed phase (RP)-high performance liquid chromatography (HPLC), mass spectrometry (MS), NMR spectroscopy, RP-HPLC-MS and RP-HPLC-NMR showed to be very useful for the separation and characterisation of the detailed structures of the substituted XOS.
The differently substituted XOS in the hydrolysates of brewery's spent grain and Eucalyptus wood were separated by anion-exchange and size-exclusion chromatography and characterised in more detail. The XOS in the brewery's spent grain hydrolysate included mainly xylan-fragments substituted with arabinoses and XOS containing only few substituents. Furthermore, arabinoxylan-fragments having O -acetyl substitution were present, suggesting the presence of O -acetyl in cereal arabinoxylans. The Eucalyptus wood hydrolysate contained mainly linear XOS, O -acetylated XOS and ( O -acetylated) XOS substituted with one or two 4- O -methylglucuronic acid(s). Additionally, a series of XOS containing both 4- O -methyl-glucuronic acid and a hexose, most likely galactose, was identified.
Degradation of structurally different non-digestible oligosaccharides by intestinal bacteria: glycosylhydrolases of Bifidobacterium adolescentis = Afbraak van in structuur verschillende niet-verteerbare oligosacchariden door darmbacteriën : glycosylhydrolasen van Bifidobacterium adolescentis
Laere, K. Van - \ 2000
Agricultural University. Promotor(en): A.G.J. Voragen; G. Beldman. - S.l. : S.n. - ISBN 9789058082305 - 152
spijsvertering - darmen - darmmicro-organismen - oligosacchariden - bacteriën - digestion - intestines - intestinal microorganisms - oligosaccharides - bacteria
Non-digestible oligosaccharides (NDOs) are oligosaccharides, which resist digestion in the upper gastrointestinal tract, and which are fermented in the colon by intestinal bacteria. Some NDOs are considered bifidogenic, meaning that they selectively stimulate the growth of bifidobacteria in the colon microbiota. The degradative fermentation of structurally different oligosaccharides by intestinal bacteria was studied in this thesis, in order to establish the potentially bifidogenic effects of various types of NDOs. Structurally different oligosaccharides were produced using different routes. Arabino-, (arabino-)galacto-, (arabino-)xylo-, galacturono-, and rhamnogalacturono- oligosaccharides were derived by enzymatic hydrolysis of plant polysaccharides. Through transglycosylation reactions using glycosidases, transgalactooligosaccharides of theα- andβ-glycosyl linkage type were obtained.
The chemical structure of the oligosaccharides clearly influenced their fermentation behaviour. It was concluded that species belonging to different groups, so not only bifidobacteria, have the capability of hydrolysing these oligosaccharides. Bi. adolescentis, being a major bifidobacterial species of the adult intestinal microflora, was able to utilise a wide range of oligosaccharides showing its wide range of glycosidases. Two novel arabinoxylan degrading enzymes were purified from Bi. adolescentis and these enzymes in combination with aβ-xylosidase are involved in the complete degradation of arabinoxylooligosaccharides. For the utilisation ofα-galactooligosaccharides Bi. adolescentis produced anα-galactosidase. Thisα-galactosidase was characterised as a retaining glycosidase and was used for the production of new types ofα-galactooligosaccharides. Theseα-1→6 linked-galactooligosaccharides could be utilised by various strains belonging to bifidobacteria and lactobacilli. Upon growth of Bi. adolescentis on transgalactooligosaccharides (TOS) a novelβ-galactosidase was produced, involved in the degradation of TOS. It was speculated that this enzyme was membrane or cell wall associated. After growth of Bi. adolescentis on TOS or on hydrolysed arabinogalactan theβ-galactosidase production of Bi. adolescentis increased compared to growth on galactose and this increasedβ-galactosidase activity could be linked to increased activity towards both polymeric and oligomeric galactan. In vivo dietary intervention with TOS also resulted in increased levels of v-galactosidase activity in feces. Although the nature and specificity of theβ-galactosidase is not yet known it can be concluded that glycosidase activity of the intestinal bacteria might be a useful biomarker of the colonic metabolic activity.
Physiology of exopolysaccharide biosynthesis by Lactococcus lactis
Looijesteijn, E. - \ 2000
Agricultural University. Promotor(en): J.A.M. de Bont; J. Hugenholtz. - S.l. : S.n. - ISBN 9789058082862 - 197
lactococcus lactis - industriële microbiologie - biosynthese - biochemie - fysiologie - oligosacchariden - koolhydraten - melkzuurbacteriën - lactococcus lactis - industrial microbiology - biosynthesis - biochemistry - physiology - oligosaccharides - carbohydrates - lactic acid bacteria
Several lactic acid bacteria (LAB) produce exopolysaccharides (EPS). EPSs produced by LAB are a potential source of natural additives and because LAB are food grade organisms, these EPSs can also be produced in situ . The amount of EPS in milk fermented with strain NIZO B40, which produces an anionic EPS composed of glucose, rhamnose, galactose and phosphate, is very low. This relatively low concentration could be increased by optimising the culture conditions and medium composition. Using pH-controlled fermentations and a chemically defined medium, the total EPS production was highest at pH 5.8 and 25 °C. Glucose was demonstrated to be the most efficient sugar source for EPS production by L. lactis NIZO B40. With fructose as the sugar source only a minor amount of EPS was produced. The intracellular levels of sugar nucleotides, the EPS precursors, were much lower in fructose- than in glucose-grown cultures. The activity of the enzymes involved in the biosynthesis of the sugar nucleotides were however unaffected by the source of sugar but the activity of fructose-1,6-bisphosphatase (FBPase) was very low. FBPase catalyses the conversion of fructose-1,6-diphosphate into fructose-6-phosphate, an essential step for the biosynthesis of sugar nucleotides from fructose but not from glucose. Overexpression of the fbp gene resulted in increased EPS synthesis on fructose.
Most culture conditions influenced growth as well as EPS formation and EPS synthesis itself was also influenced by the growth rate. EPS production by strain NIZO B40 starts at the exponential growth phase but continues during the stationary phase in batch cultures, indicating that EPS biosynthesis and growth are not strictly coupled. Indeed we found that non-growing cultures were still able to produce EPS, making it possible to study the influence of different culture conditions on EPS biosynthesis independent of growth.
The amounts of EPS produced by L. lactis NIZO B40 and NIZO B891 were comparable under glucose and leucine limitation. The efficiency of EPS production, the quantity of EPS produced per quantity of glucose consumed, was however much higher under conditions of glucose limitation. The production of phosphorylated B40 EPS and of unphosphorylated B891 EPS was strongly reduced under conditions of phosphate limitation. The sugar composition of both B40 and B891 EPS and the phosphate content of B40 EPS were unaffected by the type of limitation but surprisingly, glucose limitation resulted in the production of EPSs with strongly reduced molecular masses.
Anionic B40 EPS in suspension and a cell-associated layer of this EPS protected the bacteria against toxic copper ions and nisin, probably due to charge interactions. Furthermore, cell-associated EPS resulted in a decrease in the sensitivity of the bacteria to bacteriophages and lysozyme, most likely by masking the targets for the phages and the enzyme. The protection of EPS against nisin and bacteriophages could be a competitive advantage in mixed strain dairy starter cultures. Unfortunately, the EPS yields were not increased in the presence of copper, bacteriophages, nisin or lysozyme.
Genetic analysis of seed-soluble oligosaccharides in relation to seed storability of Arabidopsis
Bentsink, L. ; Alonso-Blanco, C. ; Vreugdenhil, D. ; Tesnier, K. ; Groot, S.P.C. ; Koornneef, M. - \ 2000
Plant Physiology 124 (2000). - ISSN 0032-0889 - p. 1595 - 1604.
uitdrogingstolerantie - oligosacchariden - zaadfysiologie - opslag van zaden - desiccation tolerance - oligosaccharides - seed physiology - seed storage
Seed oligosaccharides (OSs) and especially raffinose series OSs (RSOs) are hypothesized to play an important role in the acquisition of desiccation tolerance and consequently in seed storability. In the present work we analyzed the seed-soluble OS (sucrose, raffinose, and stachyose) content of several Arabidopsis accessions and thus identified the genotype Cape Verde Islands having a very low RSO content. By performing quantitative trait loci (QTL) mapping in a recombinant inbred line population, we found one major QTL responsible for the practically monogenic segregation of seed stachyose content. This locus also affected the content of the two other OSs, sucrose, and raffinose. Two candidate genes encoding respectively for galactinol synthase and raffinose synthase were located within the genomic region around this major QTL. In addition, three smaller-effect QTL were identified, each one specifically affecting the content of an individual OS. Seed storability was analyzed in the same recombinant inbred line population by measuring viability (germination) under two different seed aging assays: after natural aging during 4 years of dry storage at room temperature and after artificial aging induced by a controlled deterioration test. Thus, four QTL responsible for the variation of this trait were mapped. Comparison of the QTL genetic positions showed that the genomic region containing the major OS locus did not significantly affect the seed storability. We concluded that in the studied material neither RSOs nor sucrose content had a specific effect on seed storability.
Enzymatic synthesis of oligosaccharides : kinetics, process parameters, and reactor design
Boon, F. - \ 2000
Agricultural University. Promotor(en): K. van 't Riet; A. Janssen. - S.l. : S.n. - ISBN 9789058081612 - 120
oligosacchariden - biosynthese - oligosaccharides - biosynthesis
The intestinal microflora, e.g. bifidobacteria, has a strong influence on the human health. Two approaches exist to increase the number or activity of health-promoting organisms in the gastrointestinal tract. Organism (probiotics) or a selective carbon source (prebiotics) can be added to the food. Examples of prebiotics are oligosaccharides. These can be produced by enzymatic synthesis with a glycosidase as catalyst and a disaccharide as substrate.
Oligosaccharide formation using the transferase activity of glycosidases is a kinetically controlled reaction. Describing the concentrations of all reactants in time is essential for a reactor design. Along with describing the concentrations in time, more knowledge is obtained about the effect of process parameters such as substrate concentration, temperature, time, enzyme origin, and reactor configuration on the oligosaccharide synthesis. The model system used is the reaction with lactose as a substrate and a β-galactosidase as catalyst.
A galactosyl-enzyme complex based model is used to describe the concentrations in time. The effect of temperature is implemented in the kinetic model. The model is used to describe the synthesis by β-galactosidases from various mesophilic and thermophilic enzymes. Three possibilities (adsorption, membranes, and ion-exchange chromatography) are discussed to remove trisaccharides from the reaction mixture and thereby increase the yield. Finally, the possibility to produce oligosaccharides in water-miscible solvents is discussed.
Fructo-oligosachariden geen geschikte groeibevorderaars
Peet-Schwering, C. van der; Houdijk, J. ; Binnendijk, G. - \ 1999
Praktijkonderzoek varkenshouderij 13 (1999)3. - ISSN 1382-0346 - p. 25 - 27.
biggen - varkensvoeding - groei - toevoegingen - voedersupplementen - fructose - oligosacchariden - piglets - pig feeding - growth - additives - feed supplements - fructose - oligosaccharides
Fructo-oligosachariden (FOS) zijn geen geschikt alternatief voor anti-microbiële groeibevorderaars in eiwitrijk speenvoer voor biggen. Biggen die FOS in eiwitrijk voer verstrekt krijgen nemen de eerste veertien dagen van de opfokperiode minder voer open groeien langzamer dan biggen die avilamycine in het voer verstrekt krijgen