Scope: Many dietary phytochemicals have been reported to promote gut health. Specific dietary phytochemicals, such as luteolin, as well as specific microbial metabolites of tryptophan are ligands of the aryl hydrocarbon receptor (AhR), which plays a role in immunity and homeostasis of the gut barrier. Here, the fate of luteolin during colonic fermentation and the contribution of tryptophan metabolites to AhR activity in different parts of the colon are investigated.Methods and results: Several polyphenols are screened for AhR activation and oregano, containing the ligand luteolin, is added to batch cultures of human microbiota from the distal colon. Luteolin is rapidly metabolized, with no measurable increase in AhR activity. In the second experiment, using the Simulator of the Human Intestinal Microbial Ecosystem (SHIME), not all luteolin is metabolized in the ascending colon, but disappear rapidly in the transverse colon. The greatest AhR activity is due to microbiota‐derived metabolites of tryptophan, particularly in the descending colon.Conclusions: Luteolin in food is rapidly metabolized in the transverse colon. Tryptophan metabolism by the microbiota in the colon contributes substantially to the pool of lumen metabolites that can activate the AhR.

Glucosinolates in broccoli can be converted upon chewing and processing into Aryl hydrocarbon Receptor (Ahr) ligands.

The global protein demand is in constant increase requiring sustainable and healthier alternative proteins for animal and human nutrition. Yeast-based proteins (YBP) represent a non-negligible environmental-friendly fermentation-based solutions with high nutritional quality and bioavailability. Although in vitro studies cannot reflect the full complexity of in vivo digestion, it is considered as useful alternatives to animal models assessing protein digestibility. A 5 h TIM-1 digestion model (TNO Gastro-Intestinal Model) was used to assess the digestibility profile and amino acid bio-accessibility of YBP (3 separate production batches) versus whey and casein as references. Every hour, dialysate and ileal effluent samples were collected. Total nitrogen and free amino acid (FAA) were quantified. To assess the microbial impact, YBP digestate was subjected to 48 h Colon-on-a-Plate batch fermentation, after which the microbial composition by shotgun sequencing and microbial activity by Short-Chain Fatty Acids (SCFAs), Branched-Chain Fatty Acids (BCFAs) (GC-MS) and untargeted metabolomics (LA-REIMS) was analysed (from N = 11 healthy donors of faecal material). YBP, casein and whey were comparable in terms of digestibility. Although YBP showed a different metabolomic fingerprint compared to casein and whey, the microbial activity through SCFA quantification was significantly increased for all proteins compared to blank but not between protein sources. Whey and casein resulted in a higher abundance of Clostridium compared to YBP, while the treatment with YBP resulted in higher abundance of Bacteroides. Altogether, our results suggest that YBP could be a nutritionally relevant alternative protein.

Bread can vary in textural and nutritional attributes based on differences in the bread making process (e.g., flour type, fermentation agent, fermentation time). Four bread recipes (BRs) made with sourdough preferments (BR1, white flour; BR2, whole grain flour) or regular yeast breads (BR3, white flour; BR4, whole grain flour) were evaluated for texture, digestibility, and their effect on the metabolic activity and composition of the gut microbiota using texture profile analysis (TPA) coupled with in vitro upper gastrointestinal (GIT) digestion and colonic fermentation (Colon-on-a-plate™ model), using fecal samples from eight healthy human donors. TPA revealed significantly higher values for hardness, fracturability, gumminess, and chewiness, and significantly lower values for springiness, cohesiveness, and resilience with whole grain versus white breads (all p < 0.001); values for springiness, cohesiveness, and resilience were significantly higher for sourdough versus yeast bread (p < 0.001). Nutrient composition and bioaccessibility were generally comparable between sourdough and yeast bread with similar flours. Following simulation of upper GIT digestion, all BRs demonstrated good digestibility of minerals, carbohydrates, and proteins. Colonic fermentation revealed changes in gut microbiota composition, significant increases in short-chain fatty acids, and a significant decrease in branched short-chain fatty acids with all BRs versus a blank. Overall, new insights into wheat bread digestibility and colonic fermentation were provided, which are important aspects to fully characterize bread nutritional profile and potential.

Irritable bowel syndrome (IBS) is a multifactorial disorder of the gut‐brain axis, characterized by visceral hypersensitivity (VH). Psychobiotics, through GABA synthesis, are good candidates to alleviate gastrointestinal discomfort. Here, we analyzed the GABA‐producer Lactococcus lactis CNCM I‐5388 as an active‐enzyme postbiotic to relieve VH mediated by psychological stress. L. lactis CNCM I‐5388 was inactivated by ethanol while maintaining its glutamate decarboxylase (GAD) activity. This EtOH‐treated nonviable form was given daily orally for 1, 5, or 10 days to female Wistar rats in comparison with viable L. lactis CNCM I‐5388 or vehicle. Visceral sensitivity was measured by electromyography before and after partial restraint stress (PRS). GABA was quantified in the stomach collected from rats and in the gastric compartment of TIM‐1 human gut model in fed state. A daily treatment for 5 and 10 days by L. lactis CNCM I‐5388 both in its viable and nonviable forms counteracted VH promoted by PRS. However, only viable L. lactis CNCM I‐5388 tended to reduce VH after a single administration. After 5‐day treatment, only under PRS conditions, the production of GABA within the stomach was enhanced in rats treated with viable or nonviable L. lactis CNCM I‐5388. This increase was confirmed by using the TIM‐1 human gut model. We found that a postbiotic with an active‐GAD enzyme of L. lactis CNCM I‐5388, similarly to its viable psychobiotic form, exerts anti‐VH properties in an IBS‐like rat model. These effects are associated with GABA production in the stomach where the low pH promotes GAD activity.

In dogs, gut microbiome dysbiosis is associated with several health conditions, including gastrointestinal disease. Probiotic supplementation can support a balanced gut microbiome. This study assessed the impact of a probiotic containing a mixture of Lacticaseibacillus casei, Limosilactobacillus fermentum, Levilactobacillus brevis, and Enterococcus faecium on the gut microbiota of six dogs using short-term colonic simulations. Two groups were included, i.e., blank versus supplementation with the test product, and incubated for 48 h. Probiotic-supplemented reactors had significantly greater fermentative activity compared with the blank, as shown by lower pH levels and higher gas pressure after 6 h, 24 h, and 48 h of incubation (p < 0.05 for all). Saccharolytic fermentation also increased, with a significantly higher level of acetate at 24 h and propionate at 6 h, 24 h, and 48 h with the test product versus blank (p < 0.05 for all). There was no significant effect of the test product on alpha-diversity, but beta-diversity analysis revealed a clear separation in the microbial community composition between the test product and blank. Eight bacterial taxa were enriched with test product supplementation, including the probiotic test strains as well as Megamonas and Bacteroides species. This study, using in vitro short-term colon simulations with six canine donors, provides insights into the probiotic characteristics of the test product.