Evaluation of synbiotic combinations of commercial probiotic strains with different prebiotics in in vitro and ex vivo human gut microcosm model

Exploring probiotics for their crosstalk with the host microbiome through the fermentation of non-digestible dietary fibers (prebiotics) for their potential metabolic end-products, particularly short-chain fatty acids (SCFAs), is important for understanding the endogenous host-gut microbe interaction. This study was aimed at a systematic comparison of commercially available probiotics to understand their synergistic role with specific prebiotics in SCFAs production both in vitro and in the ex vivo gut microcosm model. Probiotic strains isolated from pharmacy products including Lactobacillus sporogenes (strain not labeled), Lactobacillus rhamnosus GG (ATCC53103), Streptococcus faecalis (T-110 JPC), Bacillus mesentericus (TO-AJPC), Bacillus clausii (SIN) and Saccharomyces boulardii (CNCM I-745) were assessed for their probiotic traits including survival, antibiotic susceptibility, and antibacterial activity against pathogenic strains. Our results showed that the microorganisms under study had strain-specific abilities to persist in human gastrointestinal conditions and varied anti-infective efficacy and antibiotic susceptibility. The probiotic strains displayed variation in the utilization of six different prebiotic substrates for their growth under aerobic and anaerobic conditions. Their prebiotic scores (PS) revealed which were the most suitable prebiotic carbohydrates for the growth of each strain and suggested xylooligosaccharide (XOS) was the poorest utilized among all. HPLC analysis revealed a versatile pattern of SCFAs produced as end-products of prebiotic fermentation by the strains which was influenced by growth conditions. Selected synbiotic (prebiotic and probiotic) combinations showing high PS and high total SCFAs production were tested in an ex vivo human gut microcosm model. Interestingly, significantly higher butyrate and propionate production was found only when synbiotics were applied as against when individual probiotic or prebiotics were applied alone. qRT-PCR analysis with specific primers showed that there was a significant increase in the abundance of lactobacilli and bifidobacteria with synbiotic blends compared to pre-, or probiotics alone. In conclusion, this work presents findings to suggest prebiotic combinations with different well-established probiotic strains that may be useful for developing effective synbiotic blends.