Folate Production by Streptococcus thermophilus IDCC 2201 and Its Impact on Human Gut Microbiota.

Probiotics have been extensively investigated as potential food supplements for human health benefits. Metabolites derived from probiotics are the primary factors that characterize each strain's functionality and play a crucial role in shaping their effects on the human host. In this study, we characterized the secreted metabolite profiles of sixteen commercial probiotic strains and identified Streptococcus thermophilus IDCC 2201 as a major folate producer. To investigate its effects on gut microbiota, S. thermophilus was co-cultured with individual species comprising the human gut microbial community. Specific bacteria, such as Bacteroides thetaiotaomicron, Veilonella parvula, and Ruminococcus faecis, grew dependently on both folate and S. thermophilus. These bacteria exhibited greater growth in the presence of folate than in its absence, with 2.8-, 3.6-, and 3.9-fold increases, respectively. Additionally, they showed relatively higher growth when co-cultured with S. thermophilus compared to other bacterial species, with 1.2-, 1.3-, and 1.9-fold increases, respectively. Our results indicate that the interaction between probiotics and the human gut microbiota can influence changes in ecological balance through nutrient cross-feeding, and understanding this interaction can be applied to precision probiotic therapies.