Antimutagenicity and mutagen-binding activation of mutagenic pyrolyzates by microorganisms isolated from japanese miso

The microbiological flora of miso, a traditional fermented food in Japan, were investigated. Bacteria, a yeast and a mould were isolated and identified as Pediococcus acidilactici, Leuconostoc paramesenteroides, Micrococcus halobius, Zygosaccharomyces rouxii and Aspergillus sp. P acidilactici strains were dominant bacteria in miso. The binding and antimutagenic activities of all microbial strains towards mutagenic pyrolysates were investigated. The lyophilised cells of strains of the bacteria and yeast showed the largest antimutagenic effect on 3-amino-l-methyl-[⁵H]pyrido[4,3-b]indole (Trp-P-2), but the mould was less antimutagenic than the bacteria and yeast. Most strains tested had no effective antimutagenic activity against 2-amino-3-methyl imidazo[4,5-f] quinoline (IQ). Trp-P-2 was effectively bound by all non-mould strains but binding of IQ to cells was much less effective. Among the strains tested, Leuconostoc paramesenteroides No 28 indicated the highest binding activity, not only to Trp-P-2 but also to IQ (30% binding capacity). As the concentration of Trp-P-2 was increased, the limits of binding ability of P acidilactici No 23, Z rouxii No 6 and Aspergillus sp 1 were 650, 500 and 400μg per 5 mg respectively. The binding ability and antimutagenicity for Trp-P-2 of all strains was reduced by autoclaving at 100°C for 5 min or 121°C for 15 min, by 6–20% and 7–28%, respectively. Aspergillus sp 1 was unaffected by autoclaving. The binding ability and antimutagenicity of cell walls towards Trp-P-2 was very high, being more than 85 YO effective, but it was lower than that of cytoplasm.