Safety Evaluation and In vivo Strain-Specific Functionality of Bacillus Strains Isolated from Korean Traditional Fermented Foods

Unveiling and understanding differences in physiological features below the species level may serve as an essential fast-screening tool for selecting strains that can promote a specific probiotic effect. To study the intra-species diversity ofBacillus, a genus with a wide range of enzyme activities and specificity, 190Bacillusstrains were isolated from traditional Korean fermented food products. Altogether, in the preliminary safety screening, 8 of these strains were found negative for lecithinase and hemolysis activity and were selected for further investigations. On the basis of different levels of enzyme functionalities (high or low proteolytic, amylolytic, and lipolytic (PAL) activities), twoBacillus subtilisstrains were selected for an in vivo study. Each of the two strains was separately administered at a level of 1 x 10(8)CFU per day to C57BL/6 mice that were fed 60% high-fat diet ad libitum for 8 weeks, while Xenical, an anti-obesity drug, was used as a positive control in the experimental setup.B. subtilisM34 andB. subtilisGS40a with low and high amylolytic activities, respectively, induced significantly different and contrasting physiological effects. The production of short-chain fatty acids appeared to be closely associated with a shift in the gut microbiota.