Development of a bio-functional fermented soy beverage supplemented with microbial exopolysaccharides and its effect on the human gut microbiome in vitro.

The gut microbiome plays a key role in modulating human health and well-being. Exopolysaccharides (EPS) produced by lactic acid bacteria (LAB) are emerging as novel polymers that could exert a prebiotic effect via modification of this microbiome. Thus, incorporation of EPS to enhance food functionality is of interest. This study investigates the impact of a fermented soy beverage, supplemented with EPS produced by Leuconostoc mesenteroides DSA_O or DSA_F, on the faecal microbiota as assessed using an ex vivo model of the human distal colon. The soy beverage (SM) was prepared by fermentation with Lactiplantibacillus paraplantarum GB3 followed by supplementation with EPS_O (SMO) or EPS_F (SMF). Faecal samples from healthy donors were inoculated into a faecal fermentation medium with SM, SMO and SMF and incubated anaerobically at 37 °C for 24 h. After incubation, samples were subjected to shotgun metagenomic and short-chain fatty acid (SCFA) analysis. SMO and SMF were more effective than SM at enhancing the alpha diversity of the faecal microbiota after 24 h incubation. In addition, SMO promoted the growth of the health-associated species Bifidobacterium longum and Faecalibacterium prausnitzii, the latter of which is considered a next-generation probiotic. Butyrate and propionate levels were higher in faecal samples fermented with SMO and SMF than in SM. Taken together, these preliminary results indicate a potential role of EPS produced by Leuc. mesenteroides to be used as a functional food ingredient, modulating the gut microbiome as well as increasing the levels of SCFAs.