Fermentation is an ancient food preservation process, and fermented products have been traditionally consumed in different cultures worldwide over the years. The interplay between human gut microbiota, diet and host health is widely recognized. Diet is one of the main factors modulating gut microbiota potentially with beneficial effects on human health. Fermented dairy products have received much attention, but other sources of probiotic delivery through food received far less attention. In this research, a combination of in vitro tools mimicking colonic fermentation and the intestinal epithelium have been applied to study the effect of different pasteurized and non-pasteurized water kefir products on gut microbiota, epithelial barrier function and immunomodulation. Water kefir increased beneficial short-chain fatty acid production at the microbial level, reduced detrimental proteolytic fermentation compounds and increased Bifidobacterium genus abundance. The observed benefits are enhanced by pasteurization. Pasteurized products also had a significant effect at the host level, improving inflammation-induced intestinal epithelial barrier disruption and increasing IL-10 and IL-1β compared to the control condition. Our data support the potential health benefits of water kefir and demonstrate that pasteurization, performed to prolong shelf life and stability of the product, also enhanced these benefits.

Fucoidans have demonstrated a wide range of bioactivities including immune modulation and benefits in gut health. To gain a deeper understanding on the effects of fucoidan from Undaria pinnatifida (UPF) on the colonic microbiome, the short-term Simulator of the Human Intestinal Microbial Ecosystem^®, a validated in vitro gut model, was applied. Following a three-week intervention period on adult faecal samples from three healthy donors, microbial community activity of the colonic microbiota was assessed by quantifying short-chain fatty acids while composition was analysed utilising 16S-targeted Illumina sequencing. Metagenomic data were used to describe changes in community structure. To assess the secretion of cytokines, co-culture experiments using Caco-2 and THP1-Blue™ cells were performed. UPF supplementation over a three-week period had a profound butyrogenic effect while also enriching colonic microbial diversity, consistently stimulating saccharolytic genera, and reducing genera linked with potentially negative health effects in both regions of the colon. Mild immune modulatory effects of UPF were also observed. Colonic fermentation of UPF showed anti-inflammatory properties by inducing the secretion of the anti-inflammatory cytokines IL-6 and IL-10 in two out of three donors in the proximal and distal colon. In conclusion, UPF supplementation may provide significant gut health benefits.

Several alternative proteins have emerged that may improve the environmental footprint of our food system. Evaluations into the impact of these protein sources on gastrointestinal health is limited. A study was performed to determine whether aqueous extracts from dietary protein sources, both traditional and alternative, had a differential impact on a leaky gut cell culture model. Aqueous extracts of soybean meal, fish meal, Cyberlindnera jadinii, Saccharomyces sp., Bio-Mos, Chlorella pyrenoidosa, Methylobacterium extorquens, Escherichia coli, and Hermetia illucens were administered onto a Caco-2/THP-1 co-culture and the transepithelial electrical resistance (TEER) and IL-1β, IL-6, IL-8, IL-10, TNF-α, CXCL10, and MCP-1 concentrations, and NF-κB activity were determined. Principal components analysis and K means clustering were performed. Three clusters were identified: one for soybean meal, one for bacterial meals, and one for the remaining sources. The bacterial meal cluster exhibited pro-inflammatory properties, i.e., correlated with TNF-α, IL-1β, IL-8, and NF-κB. The soybean meal cluster exhibited both pro- and anti-inflammatory properties, whereas the third cluster containing the remaining proteins exhibited anti-inflammatory properties (correlated with TEER and IL-10). These results suggest that aqueous extracts from yeast proteins contribute more positively, and bacterial proteins contribute the least positively, towards intestinal health in a leaky gut model.

Background: Rhamnogalacturonan-I (RG-I) is a pectic polysaccharide with emerging prebiotic and immunomodulatory potential. This randomised, double-blind, placebo-controlled trial (ID: NCT06081972) evaluated the effects of carrot-derived RG-I (cRG-I) supplementation, compared to placebo (maltodextrin), on gut microbiota composition and immune cell activation in healthy adults. Methods: A total of 54 participants (18–70 years old) were randomised in a double-blind manner to receive either 500 mg/day of cRG-I or placebo for four weeks. Pre-screening ensured balanced randomisation based on habitual fibre intake and faecal Bifidobacterium counts. Questionnaires assessed potential gut health and well-being effects, while in vitro and ex vivo models were used to evaluate effects on intestinal permeability. Results: cRG-I was well tolerated with excellent compliance. Faecal Bifidobacterium counts increased significantly, peaking at week 3. Isobutyric acid levels rose, though no other SCFAs differed. Immunologically, cRG-I enhanced the percentage of circulating myeloid dendritic cells expressing activation markers (CD86, HLA-DR) on. Stool consistency improved slightly. Preclinical models further showed that cRG-I and its fermentation products protected intestinal barrier integrity under stress. Conclusion: These results support cRG-I as a safe, low-dose dietary intervention capable of beneficially modulating gut microbiota, immune responses, and barrier function in healthy adults within a short supplementation period.

Single-cell protein from torula yeast (Cyberlindnera jadinii) grown on lignocellulosic biomass has been proven to be an excellent alternative protein source for animal feed. This study aimed to evaluate the amino acid (AA) digestibility by estimating intestinal absorption from three yeast-based ingredients, produced by cultivating C. jadinii on hydrolysate, using either mixed woody species (drum- (WDI) or spray-dried (WSI)) or corn dextrose (drum-dried (DDI)) as the carbon source. Further, the protective effect of intestinal digests on activated THP1-Blue™-induced epithelial damage and cytokine profile was evaluated. Total protein content from these three ingredients ranged from 34 to 45%, while the AA dialysis showed an estimated bioaccessibility between 41 and 58%, indicating good digestibility of all test products. A protective effect against epithelial-induced damage was observed for two of the three tested products. Torula yeast cultivated on wood and drum-dried (WDI) and torula yeast cultivated on wood and spray-dried (WSI) significantly increased transepithelial electrical resistance (TEER) values (111–147%, p < 0.05), recovering the epithelial barrier from the inflammation-induced damage in a dose-dependent manner. Further, WSI digests significantly reduced IL8 (250.8 ± 28.1 ng/mL), IL6 (237.9 ± 1.8 pg/mL) and TNF (2797.9 ± 216.3 pg/mL) compared to the blank control (IL8 = 485.7 ± 74.4 ng/mL, IL6 = 478.7 ± 58.9 pg/mL; TNF = 4273.5 ± 20.9 pg/mL) (p < 0.05). These results align with previous in vivo studies, supporting torula yeast-based ingredients as a high-quality protein source for pigs, protecting the intestinal barrier from inflammatory damage, and reducing the pro-inflammatory response. We provided novel insights into the mechanisms behind the health improvement of pigs fed on torula yeast-based ingredients, with potential applications for designing nutritional interventions to recover intestinal homeostasis during critical production periods, such as weaning.

While many beneficial host–microbiota interactions have been described, imbalanced microbiota in the gut is speculated to contribute to the progression and recurrence of chronic inflammatory diseases such as Crohn’s disease (CD). This in vitro study evaluated the impact of a cranberry concentrate Type M (CTM) on adherent-invasive Escherichia coli (AIEC) LF82, a pathobiont associated with CD. Different stages of pathogenic infection were investigated: (i) colonization of the mucus layer, and (ii) adhesion to and (iii) invasion of the epithelial cells. Following 48 h of fecal batch incubation, 0.5 and 1 mM of CTM significantly altered AIEC LF82 levels in a simulated mucus layer, resulting in a decrease of 50.5% in the untreated blank, down to 43.0% and 11.4%, respectively. At 1 mM of CTM, the significant decrease in the levels of AIEC LF82 coincided with a stimulation of the metabolic activity of the background microbiota. The increased levels of health-associated acetate (+7.9 mM) and propionate levels (+3.5 mM) suggested selective utilization of CTM by host microorganisms. Furthermore, 1 mM of both fermented and unfermented CTM decreased the adhesion and invasion of human-derived epithelial Caco-2 cells by AIEC LF82. Altogether, this exploratory in vitro study demonstrates the prebiotic potential of CTM and supports its antipathogenic effects through direct and/or indirect modulation of the gut microbiome.