Antimutagenic activity of several probiotic bifidobacteria against Benzo[a]pyrene

Antimutagenic activities of several probiotic bifidobacteria against a potent mutagen, benzo[a]pyrene (B[a]P), were examined by performing the modified Ames test using Salmonella typhimurium TA100. Results showed that MRS cultures of six bifidobacterial species and the cultures preincubated with mutagenic factors such as B[a]P and S9 mix displayed characteristic antimutagenic activities. Cells of Bifidobacterium lactis Bb-12 and B. longum CCRC 14634 showed higher antimutagenic activities than their supernatants. The mutagenicity of B[a]P decreased as the reaction time of cells with B[a]P, S9 mix and B[a]P metabolites increased. Crude cell walls of B. lactis and B. longum showed higher antimutagenic activities than heat-treated cells and cell extracts. Sequential preincubation studies showed that one mechanism of the antimutagenicity is desmutagenic, involving the formation of chemical complexes between bifidobacteria, B[a]P, and B[a]P metabolites and the inactivation of P450-mediated metabolism.