A synbiotic concept containing spore-forming Bacillus strains and a prebiotic fiber blend consistently enhanced metabolic activity by modulation of the gut microbiome in vitro.

A standardized in vitro simulation of the human gastrointestinal tract (M-SHIME®) was used to assess the effect of repeated daily administration of a synbiotic formulation, containing five spore-forming Bacillus strains and a prebiotic fiber blend, on the microbial activity and composition of three simulated human subjects. Firstly, while confirming recent findings, deeper phylogenetic insight was obtained in the resident M-SHIME® microbiota, demonstrating that the model maintains a diverse and representative, colon region-specific luminal and mucosal microbial community. Supplementation of the synbiotic concept increased microbial diversity in the distal colon areas, whereas specific enhancement of Bacillaceae levels was observed in the ascending colon suggesting a successful engraftment of the Bacillus spores, which probably resulted in a stimulatory effect on, among others, Bifidobacteriaceae, Lactobacillaceae, Prevotellaceae, Tannerellaceae and Faecalibacterium prausnitzii contributing directly or indirectly to stimulation of acetate, propionate and butyrate production. When compared with a previous study investigating the Bacillus strains, the generated data suggest a synergistic effect on the intestinal microbiota for the synbiotic formulation. Given the fact that the probiotic strains have been shown to impact post-prandial metabolic endotoxemia in human individuals, it might be interesting to further investigate the efficacy of the synbiotic concept in protecting against obesity-related disorders.