Food-derived Levilactobacillus brevis M3R3 as an emerging probiotic: genomic and functional study of Bile Salt Hydrolase activity

Bile salt hydrolase (BSH) deconjugates bile acids (BA), regulating lipid and glucose metabolism, and microbial homeostasis. BSH, a probiotic trait, is widespread among Lactobacillaceae gut bacteria. Levilactobacillus brevis, a probiotic species with QPS status, is found in fermented foods, with many strains exhibiting cholesterol-lowering effect linked to BSH. However, the characterization of bsh genes in L. brevis remain unclear. Here we studied the BSH activity in L. brevis strain M3R3. M3R3 genome was sequenced with Illumina platform. bsh genes were identified and kinetic growth response to BA was analyzed. bsh gene expression was determined by RT-qPCR in presence of BA compared to MRS medium. BA profiling was carried out by UHPLC/HR-MS. 78 available L. brevis bsh proteins were phylogenetically clustered into three groups (bsh1, bsh2, and bsh3), with several strains with more than one protein. Strain M3R3 had a 2.30 Mbp long genome, with 2375 CDS. Neither AMR genes nor virulence factors were found. M3R3 possessed bsh2 and bsh3 genes, expressed both in control and in presence of BA. BAs exposure decreased kinetic parameters A and λ. M3R3 completely deconjugated glycine-conjugated BAs and app. half of the tauro-conjugated BA, respectively. By combining genomics and metabolomics, we identified L. brevis M3R3 as promising BAs- modulating probiotic with two bsh proteins.