Isolation and characterization of an antimicrobial substance from Bacillus subtilis BY08 antagonistic to Bacillus cereus and Listeria monocytogenes

A wild-type bacteria producing an antimicrobial substance was isolated from Korean traditional fermented soybean paste, and identified as Bacillus subtilis. The antimicrobial substance purified by TLC, tentatively named UV254-B, displayed a specific antimicrobial activity against pathogenic Bacillus cereus and Listeria monocytogenes, without inhibiting the growth of soybean-fermenting Bacillus species. The antimicrobial substance was susceptible to proteinase K and lipase but resistant to esterase. Antimicrobial activity was observed over a wide range of pH from 3 to 11, with the maximum activity at pH 9, and thermal stability up to 80°C. The minimum inhibitory concentration of the antimicrobial substance was found to be 64 μg/mL for B. cereus and 128 μg/mL for L. monocytogenes. This antimicrobial substance has a putative molecular weight either at 1,133.6 or 1,700.5, which differs from that of other antimicrobial substances described for B. subtilis such as iturin, surfactin, fengycin, and subtilisin.