Systemic availability and metabolism of colonic-derived short-chain fatty acids in healthy subjects: a stable isotope study

The short-chain fatty acids (SCFAs), acetate, propionate and butyrate, are bacterial metabolites that mediate the interaction between the diet, the microbiota and the host. In the present study, the systemic availability of SCFAs and their incorporation into biologically relevant molecules was quantified. Known amounts of 13C-labelled acetate, propionate and butyrate were introduced in the colon of 12 healthy subjects using colon delivery capsules and plasma levels of 13C-SCFAs 13C-glucose, 13C-cholesterol and 13C-fatty acids were measured. The butyrate-producing capacity of the intestinal microbiota was also quantified. Systemic availability of colonic-administered acetate, propionate and butyrate was 36%, 9% and 2%, respectively. Conversion of acetate into butyrate (24%) was the most prevalent interconversion by the colonic microbiota and was not related to the butyrate-producing capacity in the faecal samples. Less than 1% of administered acetate was incorporated into cholesterol and <15% in fatty acids. On average, 6% of colonic propionate was incorporated into glucose. The SCFAs were mainly excreted via the lungs after oxidation to 13CO2, whereas less than 0.05% of the SCFAs were excreted into urine. These results will allow future evaluation and quantification of SCFA production from 13C-labelled fibres in the human colon by measurement of 13C-labelled SCFA concentrations in blood

Molecular identification of wheat endoxylanase inhibitor TAXI-I11The nucleotide sequence reported in this paper is available at the EMBL/GenBank/DDBJ databases (accession number AJ438880)., member of a new class of plant proteins

AbstractTriticum aestivum endoxylanase inhibitors (TAXIs) are wheat proteins that inhibit family 11 endoxylanases commonly used in different (bio)technological processes. Here, we report on the identification of the TAXI-I gene which encodes a mature protein of 381 amino acids with a calculated molecular mass of 38.8 kDa. When expressed in Escherichia coli, the recombinant protein had the specificity and inhibitory activity of natural TAXI-I, providing conclusive evidence that the isolated gene encodes an endoxylanase inhibitor. Bioinformatical analysis indicated that no conserved domains nor motifs common to other known proteins are present. Sequence analysis revealed similarity with a glycoprotein of carrot and with gene families in Arabidopsis thaliana and rice, all with unknown functions. Our data indicate that TAXI-I belongs to a newly identified class of plant proteins for which a molecular function as glycoside hydrolase inhibitor can now be suggested

Effects of a wheat bran extract containing arabinoxylan oligosaccharides on gastrointestinal health parameters in healthy adult human volunteers : a double-blind, randomised, placebo-controlled, cross-over trial

Wheat bran extract (WBE) is a food-grade soluble fibre preparation that is highly enriched in arabinoxylan oligosaccharides. In this placebo-controlled cross-over human intervention trial, tolerance and effects on colonic protein and carbohydrate fermentation were studied. After a 1-week run-in period, sixty-three healthy adult volunteers consumed 3, 10 and 0 g WBE/d for 3 weeks in a random order, with 2 weeks' washout between each treatment period. Fasting blood samples were collected at the end of the run-in period and at the end of each treatment period for analysis of haematological and clinical chemistry parameters. Additionally, subjects collected a stool sample for analysis of microbiota, SCFA and pH. A urine sample, collected over 48 h, was used for analysis of p-cresol and phenol content. Finally, the subjects completed questionnaires scoring occurrence frequency and distress severity of eighteen gastrointestinal symptoms. Urinary p-cresol excretion was significantly decreased after WBE consumption at 10 g/d. Faecal bifidobacteria levels were significantly increased after daily intake of 10 g WBE. Additionally, WBE intake at 10 g/d increased faecal SCFA concentrations and lowered faecal pH, indicating increased colonic fermentation of WBE into desired metabolites. At 10 g/d, WBE caused a mild increase in flatulence occurrence frequency and distress severity and a tendency for a mild decrease in constipation occurrence frequency. In conclusion, WBE is well tolerated at doses up to 10 g/d in healthy adults volunteers. Intake of 10 g WBE/d exerts beneficial effects on gut health parameters

Fibre-rich and wholegrain foods : improving quality/ Edit.: Jan A. Delcour; Kaisa Poutanen

459 hal.: ill, tab.; 23 cm

How to impact gluten protein network formation during wheat flour dough making

© 2019 Elsevier Ltd Gluten proteins strongly affect the structure and texture of various wheat flour-based baked goods. During dough making, gluten proteins are the main determinants of dough properties. Be it for research purposes or as a way of controlling dough properties in an industrial environment, different approaches have been taken to alter gluten network structure and, thus, functionality. In this brief review, we summarize these strategies, considering both processing-based interventions to gluten network formation and some additives commonly used to steer gluten protein functionality at the dough level.status: publishe

Fibre-rich and wholegrain foods : improving quality/ Edit.: Jan A. Delcour; Kaisa Poutanen

459 hal.: ill, tab.; 23 cm

Fractionation-reconstitution experiments provide insight into the role of endoxylanases in bread-making

The impact mechanism of endoxylanases in straight dough bread-making was investigated in fractionation-reconstitution experiments. To this end, two European flours with different breadmaking characteristics were separated in gluten, prime starch, a squeegee fraction (SQF), and a water-extractable fraction. Whereas the former fractions contained negligible levels of arabinoxylan (AX), the latter contained, respectively, most of the water-unextractable AX (WU-AX) and all of the water-extractable AX (WE-AX). In vitro modification with a Bacillus Subtilis endoxylanase allowed controlled solubilization of WU-AX from SQF and controlled degradation of solubilized AX and WE-AX from the water-extractables. It followed from bread-making tests with the reconstituted flours that endoxylanases exert positive loaf volume effects in bread-making by lowering the concentration of WU-AX and increasing that of total soluble AX Limited degradation of WE-AX and significant breakdown of solubilized AX by endoxylanases, on the other hand, resulted in volume lasses when compared to their nondegraded counterparts. The volume increasing effects of endoxylanases are therefore related to their ratio of solubilizing to degrading activity and thus to their substrate specificity.status: publishe