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Staff Publications

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

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

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

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    Genome-wide association study for genotype by lactation stage interaction of milk production traits in dairy cattle
    Lu, Haibo ; Wang, Yachun ; Bovenhuis, Henk - \ 2020
    Journal of Dairy Science (2020). - ISSN 0022-0302
    genetic background - genome-wide association study (GWAS) - lactose - negative energy balance - pregnancy

    Substantial evidence demonstrates that the genetic background of milk production traits changes during lactation. However, most GWAS for milk production traits assume that genetic effects are constant during lactation and therefore might miss those quantitative trait loci (QTL) whose effects change during lactation. The GWAS for genotype by lactation stage interaction are aimed at explicitly detecting the QTL whose effects change during lactation. The purpose of this study was to perform GWAS for genotype by lactation stage interaction for milk yield, lactose yield, lactose content, fat yield, fat content, protein yield, and somatic cell score to detect QTL with changing effects during lactation. For this study, 19,286 test-day records of 1,800 first-parity Dutch Holstein cows were available and cows were genotyped using a 50K SNP panel. A total of 7 genomic regions with effects that change during lactation were detected in the GWAS for genotype by lactation stage interaction. Two regions on Bos taurus autosome (BTA)14 and BTA19 were also significant based on a GWAS that assumed constant genetic effects during lactation. Five regions on BTA4, BTA10, BTA11, BTA16, and BTA23 were only significant in the GWAS for genotype by lactation stage interaction. The biological mechanisms that cause these changes in genetic effects are still unknown, but negative energy balance and effects of pregnancy may play a role. These findings increase our understanding of the genetic background of lactation and may contribute to the development of better management indicators based on milk composition.

    Genome-wide association study for genotype by lactation stage interaction of milk production traits in dairy cattle
    Lu, Haibo ; Wang, Yachun ; Bovenhuis, Henk - \ 2020
    Journal of Dairy Science 103 (2020)6. - ISSN 0022-0302 - p. 5234 - 5245.
    genetic background - genome-wide association study (GWAS) - lactose - negative energy balance - pregnancy

    Substantial evidence demonstrates that the genetic background of milk production traits changes during lactation. However, most GWAS for milk production traits assume that genetic effects are constant during lactation and therefore might miss those quantitative trait loci (QTL) whose effects change during lactation. The GWAS for genotype by lactation stage interaction are aimed at explicitly detecting the QTL whose effects change during lactation. The purpose of this study was to perform GWAS for genotype by lactation stage interaction for milk yield, lactose yield, lactose content, fat yield, fat content, protein yield, and somatic cell score to detect QTL with changing effects during lactation. For this study, 19,286 test-day records of 1,800 first-parity Dutch Holstein cows were available and cows were genotyped using a 50K SNP panel. A total of 7 genomic regions with effects that change during lactation were detected in the GWAS for genotype by lactation stage interaction. Two regions on Bos taurus autosome (BTA)14 and BTA19 were also significant based on a GWAS that assumed constant genetic effects during lactation. Five regions on BTA4, BTA10, BTA11, BTA16, and BTA23 were only significant in the GWAS for genotype by lactation stage interaction. The biological mechanisms that cause these changes in genetic effects are still unknown, but negative energy balance and effects of pregnancy may play a role. These findings increase our understanding of the genetic background of lactation and may contribute to the development of better management indicators based on milk composition.

    Effects of exchanging lactose for fat in milk replacer on ad libitum feed intake and growth performance in dairy calves
    Berends, H. ; Laar, H. van; Leal, L.N. ; Gerrits, W.J.J. ; Martín-Tereso, J. - \ 2020
    Journal of Dairy Science 103 (2020). - ISSN 0022-0302 - p. 4275 - 4287.
    calf - fat - growth - lactose - milk replacer

    The recent trend in the dairy industry toward ad libitum feeding of young calves merits reconsideration of calf milk replacer (CMR) formulations. Additionally, feed intake regulation in young calves provided with ad libitum milk and solid feeds is insufficiently understood. This study was designed to determine the effect of exchanging lactose for fat in CMR on voluntary feed intake and growth performance. Lactose was exchanged for fat on a weight/weight basis, resulting in different energy contents per kilogram of CMR. Thirty-two male calves (1.7 ± 0.12 d of age, 47.6 ± 0.83 kg of body weight) were assigned to 1 of 16 blocks based on arrival date. Within each block, calves were randomly assigned to 1 of 2 treatments. The experimental period was divided into 4 periods. In period 1, until 14 ± 1.7 d of age, calves were individually housed, restricted-fed their assigned CMR treatments at 2.5 to 3 L twice daily, and provided with unlimited access to water, chopped straw, and starter. In period 2, calves were group-housed with 8 calves per pen and received ad libitum access to their assigned CMR treatments, starter feed, chopped wheat straw, and water. During period 3, from 43 until 63 d of age, calves were weaned by restricting CMR allowance in 2 steps, maintaining access to all other feeds. All calves were completely weaned at d 64 of age and were monitored until 77 d of age (period 4). Measurements included the intake of all dietary components, body weight gain, and a selection of blood traits. Increasing fat content at the expense of lactose decreased CMR intake by 10%, whereas total calculated metabolizable energy intake and growth remained equal between treatments. Total solid feed (starter and straw) consumption was not affected by CMR composition. These data indicate that calves fed ad libitum regulate their CMR intake based on energy content. High-fat CMR increased plasma phosphate, nonesterified fatty acids, triglycerides, and bilirubin, whereas plasma glucose remained unchanged. Despite the limited animal numbers in the present experiment, there was a significant decrease in the total number of health events (mainly respiratory) requiring therapeutic intervention and in the total number of therapeutic interventions in calves fed high-fat CMR. Calves appeared to consume CMR based on energy content, with a difference in ad libitum intake proportional to the difference in energy content of the CMR, maintaining equal body weight gain and solid feed intake.

    Replacing Part of Glucose with Galactose in the Postweaning Diet Protects Female But Not Male Mice from High-Fat Diet-Induced Adiposity in Later Life
    Bouwman, Lianne M.S. ; Fernández-Calleja, José M.S. ; Stelt, Inge van der; Oosting, Annemarie ; Keijer, Jaap ; Schothorst, Evert M. van - \ 2019
    The Journal of Nutrition 149 (2019)7. - ISSN 0022-3166 - p. 1140 - 1148.
    adipose tissue - galactose - insulin signaling - lactose - postweaning - programming

    BACKGROUND: Duration of breastfeeding is positively associated with decreased adiposity and increased metabolic health in later life, which might be related to galactose. OBJECTIVE: The aim of this study was to investigate if partial replacement of glucose with galactose in the postweaning diet had a metabolic programming effect. METHODS: Male and female mice (C57BL/6JRccHsd) received an isocaloric diet (16 energy% fat; 64 energy% carbohydrates; 20 energy% protein) with either glucose (32 energy%) (GLU) or glucose + galactose (GLU + GAL, 16 energy% each) for 3 wk postweaning. Afterwards, all mice were switched to the same 40 energy% high-fat diet (HFD) for 9 wk to evaluate potential programming effects in an obesogenic environment. Data were analyzed within sex. RESULTS: Female body weight (-14%) and fat mass (-47%) were significantly lower at the end of the HFD period (both P < 0.001) among those fed GLU + GAL than among those fed GLU; effects in males were in line with these findings but nonsignificant. Food intake was affected in GLU + GAL-fed females (+8% on postweaning diet, -9% on HFD) compared with GLU-fed females, but not for hypothalamic transcript levels at endpoint. Also, in GLU + GAL-fed females, serum insulin concentrations (-48%, P < 0.05) and the associated homeostasis model assessment of insulin resistance (HOMA-IR) were significantly lower ( P < 0.05) at endpoint, but there were no changes in pancreas morphology. In GLU + GAL-fed females, expression of insulin receptor substrate 2 (Irs2) (-27%, P < 0.01 ; -44%, P < 0.001) and the adipocyte size markers leptin (Lep) (-40%, P < 0.05; -63% , P < 0.05) and mesoderm-specific transcript homolog protein (Mest) (-80%, P < 0.05; -72%, P < 0.05) was lower in gonadal and subcutaneous white adipose tissue (WAT), respectively. Expression of insulin receptor substrate1 (Irs1) (-24%, P < 0.05) was only lower in subcutaneous WAT in GLU + GAL-fed females. CONCLUSIONS: Partial replacement of glucose with galactose, resulting in a 1:1 ratio mimicking lactose, in a 3-wk postweaning diet lowered body weight, adiposity, HOMA-IR, and expression of WAT insulin signaling in HFD-challenged female mice in later life. This suggests that prolonged galactose intake may improve metabolic and overall health in later life.

    Effect of energy source in calf milk replacer on performance, digestibility, and gut permeability in rearing calves
    Amado, L. ; Berends, H. ; Leal, L.N. ; Wilms, J. ; Laar, H. Van; Gerrits, W.J.J. ; Martín-Tereso, J. - \ 2019
    Journal of Dairy Science 102 (2019)5. - ISSN 0022-0302 - p. 3994 - 4001.
    calf milk replacer - fat - gut permeability - lactose

    Current calf milk replacer (CMR) compositions significantly differ from whole milk in their levels of energy, protein, and minerals. Energy source is one of the major differences, as CMR contains high levels of lactose, whereas whole milk contains higher levels of fat. The aim of this study was to determine the effect of partially exchanging lactose for fat on performance, digestibility, and gut permeability in calves fed twice daily on a high feeding plane. Lactose and fat were exchanged in the CMR formulation on a weight–weight basis. The CMR were isonitrogenous but not isoenergetic. A total of 60 male Holstein-Friesian calves were assigned to 1 of 30 blocks based on serum IgG, body weight, and date of collection after birth. Within each block, calves were randomly assigned to 1 of 2 treatments: high fat and high lactose. The CMR was provided twice daily until 49 d of age, followed by a gradual weaning period of 14 d. Starter, straw, and water were available ad libitum throughout the complete study. Exchanging lactose for fat did not affect growth; intakes of starter, straw, water, crude protein, or total energy; or apparent total-tract digestibility of nutrients. Gastrointestinal permeability was assessed by measuring the recovery of lactulose and Cr in 24-h urine and the Cr concentration and lactulose:D-mannitol ratio in serum following an oral pulse dose. Urinary recoveries of Cr and lactulose were generally low in both treatments but were higher in calves fed the high-fat CMR. Accordingly, the serum lactulose:D-mannitol ratio and serum Cr concentrations were higher in calves fed the high-fat CMR. In wk 1 and during the weaning transition, calves fed the high-fat CMR had significantly fewer abnormal fecal scores. In conclusion, exchanging lactose for fat in the CMR did not affect growth performance, total feed intake, or nutrient digestibility. The high-fat CMR was associated with an increase in permeability markers but positively influenced fecal scores in calves.

    Generation of Soluble Advanced Glycation End Products Receptor (sRAGE)-Binding Ligands during Extensive Heat Treatment of Whey Protein/Lactose Mixtures Is Dependent on Glycation and Aggregation
    Liu, Fahui ; Teodorowicz, Gosia ; Wichers, Harry J. ; Boekel, Tiny van; Hettinga, Kasper A. - \ 2016
    Journal of Agricultural and Food Chemistry 64 (2016)33. - ISSN 0021-8561 - p. 6477 - 6486.
    advanced glycation end products - digestion - lactose - Maillard reaction - whey proteins

    Heating of protein- and sugar-containing materials is considered the primary factor affecting the formation of advanced glycation end products (AGEs). This study aimed to investigate the influence of heating conditions, digestion, and aggregation on the binding capacity of AGEs to the soluble AGE receptor (sRAGE). Samples consisting of mixtures of whey protein and lactose were heated at 130 °C. An in vitro infant digestion model was used to study the influence of heat treatment on the digestibility of whey proteins. The amount of sRAGE-binding ligands before and after digestion was measured by an ELISA-based sRAGE-binding assay. Water activity did not significantly affect the extent of digestibility of whey proteins dry heated at pH 5 (ranging from 3.3 ± 0.2 to 3.6 ± 0.1% for gastric digestion and from 53.5 ± 1.5 to 64.7 ± 1.1% for duodenal digestion), but there were differences in cleavage patterns of peptides among the samples heated at different pH values. Formation of sRAGE-binding ligands depended on the formation of aggregates and was limited in the samples heated at pH 5. Moreover, the sRAGE-binding activity of digested sample was changed by protease degradation and correlated with the digestibility of samples. In conclusion, generation of sRAGE-binding ligands during extensive heat treatment of whey protein/lactose mixtures is limited in acidic heating condition and dependent on glycation and aggregation.

    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.

    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.

    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.

    Characterization of ß-Galactosidase Isoforms from Bacillus circulans and Their Contribution to GOS Production
    Warmerdam, A. ; Paudel, E. ; Wanqing, J. ; Boom, R.M. ; Janssen, A.E.M. - \ 2013
    Applied Biochemistry and Biotechnology 170 (2013)2. - ISSN 0273-2289 - p. 340 - 358.
    A ß-galactosidase preparation from Bacillus circulans consists of four isoforms called ß-gal-A, ß-gal-B, ß-gal-C, and ß-gal-D. These isoforms differ in lactose hydrolysis and galacto-oligosaccharide (GOS) synthesis at low substrate concentrations. For this reason, using a selection of the isoforms may be relevant for GOS production, which is typically done at high substrate concentrations. At initial lactose concentrations in between 0.44% and 0.68% (w/w), ß-gal-A showed the least oligosaccharide formation, followed by ß-gal-B and ß-gal-C; most oligosaccharides were formed by ß-gal-D. The differences in behavior were confirmed by studying the thermodynamics of lactose conversion with isothermal titration calorimetry since especially ß-gal-A showed a different profile than the other isoforms. Also during the conversion of allolactose and 4-galactosyllactose at 0.44 % and 0.61 % (w/w), respectively, ß-gal-A and ß-gal-D showed clear differences. In contrast to above findings, the selectivity of the isoforms did hardly differ at an initial lactose concentration of 30 % (w/w), except for a slightly higher production of galactose with ß-gal-A. These differences were hypothesized to be related to the different accessibility of the active sites of the isoforms for different-sized reactants. The initial GOS formation rates of the isoforms indicate that ß-gal-A and ß-gal-B are the best isoforms for GOS production at high lactose concentrations
    Effecten van eenvoudige koolhydraten en fermenteerbare koolhydraten op de binnentoom variatie bij varkens
    Wientjes, J.G.M. ; Soede, N.M. ; Brand, H. van den; Kemp, B. - \ 2010
    Wageningen : Adaptation Physiology Group, Wageningen University - 73
    varkens - zeugenvoeding - voersamenstelling - insuline - lactose - sucrose - suikerbieten - follikels - geboortegewicht - biggen - pigs - sow feeding - feed formulation - insulin - lactose - sucrose - sugarbeet - follicles - birth weight - piglets
    2 proeven werden uitgevoerd. Het doel van de 1e was nader inzicht te krijgen in het mechanisme dat ten grondslag ligt aan de relatie tussen insuline-stimulerend voer (dextrose+lactose) tijdens het interval spenenovulatie, follikelontwikkeling in de laatste dagen voor inseminatie en (variatie in) ontwikkeling van embryo's tijdens de vroege dracht. Het doel van de 2e proef was om nader inzicht te krijgen in de directe effecten van de specifieke voercomponenten dextrose, lactose, sucrose en suikerbietenpulp (zowel apart als gecombineerd) op glucose, insuline en IGF-1 profielen in zeugen om zo diëten te vinden met de hoogste potentie om insuline en IGF-1 afgifte te stimuleren.
    Effect van suiker plus lactose in biologisch zeugenvoer op de reproductie van zeugen en de variatie in geboortegewicht van biggen = Effects of sugar plus lactose in organic sow diets on reproductive performance and within liter birth weight variation
    Peet-Schwering, C.M.C. van der; Binnendijk, G.P. - \ 2010
    Wageningen : Wageningen UR Livestock Research (Rapport / Wageningen UR Livestock Research 377) - 20
    biologische landbouw - varkenshouderij - zeugen - veevoeding - lactose - suiker - geboortegewicht - varkensvoeding - organic farming - pig farming - sows - livestock feeding - lactose - sugar - birth weight - pig feeding
    The effects of feeding sows lactose plus sugar during lactation and the weaning-to-estrus interval on subsequent reproductive performance and within-litter variation were investigated. The results of the trial are described in this report.
    CE-LIF-MSn profiling of oligosaccharides in human milk and feces of breast-fed babies
    Albrecht, S.A. ; Schols, H.A. ; Heuvel, E.G.H.M. van den; Voragen, A.G.J. ; Gruppen, H. - \ 2010
    Electrophoresis 31 (2010)7. - ISSN 0173-0835 - p. 1264 - 1273.
    induced fluorescence detection - capillary-electrophoresis - mass-spectrometry - fed infants - sialylated oligosaccharides - liquid-chromatography - preterm - lactose - electrochromatography - combination
    Mixtures of the complex human milk oligosaccharides (HMOs) are difficult to analyze and gastrointestinal bioconversion products of HMOs may complicate analysis even more. Their analysis, therefore, requires the combination of a sensitive and high-resolution separation technique with a mass identification tool. This study introduces for the first time the hyphenation of CE with an electrospray mass spectrometer, capable to perform multiple MS analysis (ESI-MSn) for the separation and characterization of HMOs in breast milk and feces of breast-fed babies. LIF was used for on- and off-line detections. From the overall 47 peaks detected in off-line CE-LIF electropherograms, 21 peaks could be unambiguously and 11 peaks could be tentatively assigned. The detailed structural characterization of a novel lacto-N-neo-tetraose isomer and a novel lacto-N-fucopentaose isomer was established in baby feces and pointed to gastrointestinal hydrolysis of higher-Mw HMOs. CE-LIF-ESI-MSn presents, therefore, a useful tool which contributes to an advanced understanding on the fate of individual HMOs during their gastrointestinal passage.
    Influence of Roasting on the Antioxidant Activity and HMF Formation of a Cocoa Bean Model Systems
    Oliviero, T. ; Capuano, E. ; Cämmerer, B. ; Fogliano, V. - \ 2009
    Journal of Agricultural and Food Chemistry 57 (2009)1. - ISSN 0021-8561 - p. 147 - 152.
    maillard reaction-products - coffee - glycosylation - melanoidins - components - capacity - glycine - lactose - xylose - color
    During the roasting of cocoa beans chemical reactions lead to the formation of Maillard reaction (MR) products and to the degradation of catechin-containing compounds, which are very abundant in these seeds. To study the modifications occurring during thermal treatment of fat and antioxidant rich foods, such as cocoa, a dry model system was set up and roasted at 180 °C for different times. The role played in the formation of MR products and in the antioxidant activity of the system by proteins, catechin, and cocoa butter was investigated by varying the model system formulation. Results showed that the antioxidant activity decreased during roasting, paralleling catechin concentration, thus suggesting that this compound is mainly responsible for the antioxidant activity of roasted cocoa beans. Model system browning was significantly higher in the presence of catechin, which contributed to the formation of water-insoluble melanoidins, which are mainly responsible for browning. HMF concentration was higher in casein-containing systems, and its formation was strongly inhibited in the presence of catechin. No effects related to the degree of lipid oxidation could be observed. Data from model systems obtained by replacing fat with water showed a much lower rate of MR development and catechin degradation but the same inhibitory effect of catechin on HMF formation.
    Analysis of functional properties of Lactobacillus acidophilus
    Zhao, R.X. ; Sun, J.L. ; Mo, H.Z. ; Yang Zhu, Yang - \ 2007
    World Journal of Microbiology and Biotechnology 23 (2007)2. - ISSN 0959-3993 - p. 195 - 200.
    lactic-acid bacteria - diarrhea - humans - ingestion - culture - lactose - gg
    Metabolites from Lactobacillus acidophilus were analysed. The results showed that Lactobacillus acidophilus Ind-1 and Lactobacillus acidophilus Lakcid produced respectively 12.73 g and 13.33 g lactic acid l¿1 after incubating in skim milk at 37 °C for 36 h; and 2.229 unit and 1.808 unit ß-galactosidase l¿1 in an MRS medium. The proteolytic activity of Lactobacillus acidophilus was high and the content of 17 free amino acids in the fermented milk of Lactobacillus acidophilus Ind-1 and Lactobacillus acidophilus Lakcid was 394.4 mg l¿1 and 563.2 mg l¿1, respectively. Meantime, Lactobacillus acidophilus reduced cholesterol level in an MRS medium supplemented with cholesterol. Furthermore, Lactobacillus acidophilus Ind-1 and Lactobacillus acidophilus Lakcid showed antimicrobial activity against Bacillus anthracis and Escherichia coli
    Air dispersion of starch-protein mixtures : a predictive tool for air classification performance
    Dijkink, B.H. ; Speranza, L. ; Paltsidis, D. ; Vereijken, J.M. - \ 2007
    Powder Technology 172 (2007)2. - ISSN 0032-5910 - p. 113 - 119.
    relative-humidity - pranlukast hydrate - particle adhesion - dry - lactose - force - peas - removal - powders
    Milling and air classification is a well-known procedure to obtain protein and starch enriched fractions from cereals and grain legumes. Adhesion of small protein particles to larger starch granules adversely affects the separation efficiency during air classification. To gain insight into this phenomenon the dispersion of bimodal mixtures of starch granules and fine protein particles in an air stream was studied. Using a method to correct for the number of small starch particles in the protein fraction, the dispersability of protein/starch mixtures was determined. The type of protein and, particularly, of starch may affect dispersability. The effect of starch type is not only caused by differences in granule size; likely other properties such as roughness are also involved. Increasing protein content enhances dispersability but does not seem to have an effect on the adhesion between starch and protein particles itself. An increase in adhesion by relative humidity of 90% results in a decreased dispersability. The dispersability of the mixtures was related to their performance upon air classification. Both the separation efficiency and tau were strongly related to dispersability (R2 = 0.86 and 0.88 respectively). Hence, the dispersability, which can easily be measured, is a powerful tool to predict the air classification performance for separation of starch and protein.
    An efficient glycosylation reaction for the synthesis of asialo GM2 analogues
    Sun, B. ; Pukin, A.V. ; Visser, G.M. ; Zuilhof, H. - \ 2006
    Tetrahedron Letters 47 (2006)41. - ISSN 0040-4039 - p. 7371 - 7374.
    cystic-fibrosis - glycosidation - oligosaccharides - tetrasaccharide - derivatives - lactose - gm(1)
    We investigated the coupling reaction of glycosyl donors N-trichloroethoxycarbonyl-galactosamine-O-trichloroacetimidate (2a) and N-p-nitrobenzyloxycarbonyl-galactosamine-O-trichloroacetimidate (2b) with the 4¿-OH of lactose derivatives (3a¿d) to synthesize key intermediates of asialo GM2 analogues, and found that the glycosylation yield with 2a was 90% or more in all investigated cases.
    Kinetic modelling of reactions in heated disaccharide-casein systems
    Brands, C.M.J. ; Boekel, M.A.J.S. van - \ 2003
    Food Chemistry 83 (2003). - ISSN 0308-8146 - p. 13 - 26.
    maillard reaction - milk - lactose - sugar - degradation
    The reactions occurring in disaccharide-casein reaction mixtures during heating at 120 degreesC and pH 6.8 were studied. The existence of two main degradation routes were established: (1) Isomerisation of the aldose sugars lactose and maltose in their ketose isomers lactulose and maltulose, respectively, and subsequent degradation. Lactulose was degraded into galactose and formic acid, whereas maltulose was degraded into glucose and formic acid among other unidentified reaction compounds. (2) The Maillard reaction, in which the aldose sugars and sugar degradation products react with the protein, eventually leading to the formation of brown compounds. Based on these reactions a kinetic model was built and extensively tested using multiresponse modelling. The iterative process of kinetic modelling-proposing a model, confronting it with experiments and criticising the model-was passed through several times. The final kinetic model was able to describe the observed changes in reactants and products and allowed a quantitative prediction of reactions in heated disaccharide-casein systems. (C) 2003 Elsevier Ltd. All rights reserved.
    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.
    Maillard reactions and increased enzyme inactivation during oligosaccharide synthesis by a hyperthermophilic glycosidase
    Bruins, M.E. ; Hellemond, E.W. van; Janssen, A.E.M. ; Boom, R.M. - \ 2003
    Biotechnology and Bioengineering 81 (2003)5. - ISSN 0006-3592 - p. 546 - 552.
    thermostable beta-glycosidases - high-temperature process - pyrococcus-furiosus - kinetic-model - glucosidase - hydrolysis - glycine - lactose - lysine - foods
    The thermostable Pyrococcus furiosus beta-glycosidase was used for oligosaccharide production from lactose in a kinetically controlled reaction. Our experiments showed that higher temperatures are beneficial for the absolute as well as relative oligosaccharide yield. However, at reaction temperatures of 80degreesC and higher, the inactivation rate of the enzyme in the presence of sugars was increased by a factor of 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 modeled by a cascade of a zeroth- and first-order 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. (C) 2003 Wiley Periodicals.
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