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Wageningen, Netherlands

De Graaf A.A.,Top Institute Food and Nutrition | De Graaf A.A.,Maastricht University | De Graaf A.A.,TNO | Maathuis A.,Top Institute Food and Nutrition | And 11 more authors.
NMR in Biomedicine | Year: 2010

This study introduces a stable-isotope metabolic approach employing [U-13C]glucose that, as a novelty, allows selective profiling of the human intestinal microbial metabolic products of carbohydrate food components, as well as the measurement of the kinetics of their formation pathways, in a single experiment. A well-established, validated in vitro model of human intestinal fermentation was inoculated with standardized gastrointestinal microbiota from volunteers. After culture stabilization, [U-13C] glucose was added as an isotopically labeled metabolic precursor. System lumen and dialysate samples were taken at regular intervals. Metabolite concentrations and isotopic labeling were determined by NMR, GC, and enzymatic methods. The main microbial metabolites were lactate, acetate, butyrate, formate, ethanol, and glycerol. They together accounted for a 13C recovery rate as high as 91.2%. Using an NMR chemical shift prediction approach, several minor products that showed 13C incorporation were identified as organic acids, amino acids, and various alcohols. Using computer modeling of the 12C contents and 13C labeling kinetics, the metabolic fluxes in the gut microbial pathways for synthesis of lactate, formate, acetate, and butyrate were determined separately for glucose and unlabeled background substrates. This novel approach enables the study of the modulation of human intestinal function by single nutrients, providing a new rational basis for achieving control of the short-chain fatty acids profile by manipulating substrate and microbiota composition in a purposeful manner. Copyright © 2009 John Wiley & Sons, Ltd.

Stepan A.M.,Chalmers University of Technology | Hoije A.,Chalmers University of Technology | Schols H.A.,Wageningen University | De Waard P.,Wageningen Center | Gatenholm P.,Chalmers University of Technology
Journal of Applied Polymer Science | Year: 2012

Arabinoxylans (AX) from rye were partly debranched by chemical hydrolysis methods, and AXs differing in arabinosyl substitution were acetylated using chemical methods. The resulting materials are film forming, and these films underwent molecular structural analysis and were tested for their material properties. The composition and structure of the modified polymers were determined using high performance anion exchange chromatography and two dimensional nuclear magnetic resonance; it was shown that all free hydroxyl groups (of both xylose and arabinose) were acetylated. Further characterizations were done by dynamic mechanical analysis and thermo-gravimetric analysis to evaluate the thermal behavior of the material. The observed glass transition temperatures (T g) increased with a decrease in arabinosyl substitutions. The thermal degradation temperatures were all close to 380°C. The mechanical properties were characterized with tensile tests of the films. Tensile tests showed that the strain at break, which reflects the flexibility of the material, was significantly higher at higher arabinosyl substitution levels. The elastic Young's modulus was not significantly affected, although a tendency was seen toward a less stiff material at higher arabinosyl substitution. The ultimate strength of the materials was remarkably high in all cases, around 60 MPa, with little difference between them. Considering these properties, a great potential is foreseen in the application of acetylated arabinoxylans as packaging films and as matrix for composites. © 2012 Wiley Periodicals, Inc.

Ter Haar R.,Wageningen University | Wildschut J.,University of Groningen | Sugih A.K.,University of Groningen | Bart Moller W.,Wageningen University | And 6 more authors.
Carbohydrate Research | Year: 2011

To enable enzymatic coupling of saccharides to proteins, several di- and trisaccharides were hydroxy-arylated using anhydrous transesterification with methyl 3-(4-hydroxyphenyl)propionate, catalyzed by potassium carbonate. This transesterification resulted in the attachment of up to 3 hydroxy-aryl units per oligosaccharide molecule, with the monosubstituted product being by far the most abundant. The alkaline reaction conditions, however, resulted in a partial breakdown of reducing sugars. This breakdown could easily be bypassed by a preceding sugar reduction step converting them to polyols. Hydroxy-arylated products were purified by using solid phase extraction, based on the number of hydroxy-aryl moieties attached. Monohydroxy-arylated saccharose was subsequently linked to a tyrosine-containing tripeptide using horseradish peroxidase, as monitored by LC-MSn. This proof of principle for peptide and protein glycation with a range of possible saccharides and glycosidic polyols can lead to products with unique new properties. © 2011 Elsevier Ltd. All rights reserved.

Appeldoorn M.M.,Wageningen University | De Waard P.,Wageningen Center | Kabel M.A.,Wageningen University | Gruppen H.,Wageningen University | Schols H.A.,Wageningen University
Carbohydrate Research | Year: 2013

In order to use corn fiber as a source for bioethanol production the enzymatic hydrolysis of the complex glucuronoarabinoxylans present has to be improved. Several oligosaccharides present in the supernatant of mild acid pretreated and enzymatically saccharified corn fiber that resist the current available enzymes were (semi)purified for structural analysis by NMR or ESI-MSn. The structural features of 21 recalcitrant oligosaccharides are presented. A common feature of almost all these oligosaccharides is that they contain (part of) an α-l-galactopyranosyl-(1→2)-β-d- xylopyranosyl-(1→2)-5-O-trans-feruloyl-l-arabinofuranose side chain attached to the O-3 position of the β-1-4 linked xylose backbone. Several of the identified oligosaccharides contained an ethyl group at the reducing end hypothesized to be formed during SSF. The ethyl glycosides found are far more complex than previously described structures. A new feature present in more than half of the oligosaccharides is an acetyl group attached to the O-2 position of the same xylose to which the oligomeric side chain was attached to the O-3 position. Finding enzymes attacking these large side chains and the dense substituted xylan backbone will boost the hydrolysis of corn fiber glucuronoxylan. © 2013 Elsevier Ltd. All rights reserved.

Bui T.P.N.,Wageningen University | Ritari J.,University of Helsinki | Boeren S.,Wageningen University | De Waard P.,Wageningen Center | And 3 more authors.
Nature Communications | Year: 2015

Human intestinal bacteria produce butyrate, which has signalling properties and can be used as energy source by enterocytes thus influencing colonic health. However, the pathways and the identity of bacteria involved in this process remain unclear. Here we describe the isolation from the human intestine of Intestinimonas strain AF211, a bacterium that can convert lysine stoichiometrically into butyrate and acetate when grown in a synthetic medium. Intestinimonas AF211 also converts the Amadori product fructoselysine, which is abundantly formed in heated foods via the Maillard reaction, into butyrate. The butyrogenic pathway includes a specific CoA transferase that is overproduced during growth on lysine. Bacteria related to Intestinimonas AF211 as well as the genetic coding capacity for fructoselysine conversion are abundantly present in colonic samples from some healthy human subjects. Our results indicate that protein can serve as a source of butyrate in the human colon, and its conversion by Intestinimonas AF211 and related butyrogens may protect the host from the undesired side effects of Amadori reaction products.

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