Evaluation of probiotic and prebiotic-like effects of <i>Bacillus subtilis</i> BN on growth of lactobacilli

The aim of this study was to determine the probiotic and the prebiotic-like properties of Bacillus subtilis BN, a spore-forming bacterium, also known as "natto-kin", which is used for making the Japanese fermented food, natto. We used the spores and vegetative cells of this strain and compared their effects on the growth of lactobacilli. Culture supernatant from B. subtilis BN was added to a glucose-free MRS medium used to culture lactobacilli. When lactobacilli were cultured in the supernatant-containing medium, growth was improved. This effect resulted from the digestion of starch by amylase, which was secreted by B. subtilis. Moreover, improved amylase-independent growth was also observed. Co-culture with B. subtilis improved the growth of lactobacilli, and this effect was only observed with vegetative cells; spores did not improve the growth of lactobacilli. This effect on growth was lost upon heat treatment of the vegetative cells. These results suggest that the surface protein of B. subtilis BN vegetative cells participates in the improved growth effect of lactobacilli. It is possible that B. subtilis BN could improve the intestinal flora. In addition, B. subtilis BN inhibited the growth of Salmonella enterica. Thus, it was shown that B. subtilis BN has both a probiotic and prebiotic potential. This is the first study demonstrating the selective growth improvement of indigenous intestinal lactobacilli using B. subtilis BN.