Properties of a bacteriocin from Bacillus subtilis H27 isolated from Cheonggukjang

Abstract

Bacillus subtilis H27, an isolate from a commercial cheonggukjang product, inhibited Listeria monocytogenes ATCC 19111 and Bacillus cereus ATCC 14579. Antimicrobial activity of culture supernatant was completely destroyed by proteinase K treatment, indicating the proteinaceous nature of the inhibitory substance. The bacteriocin, Bac H27, was most stable at pH 7 and stable between pH 3-6 and 8-9 but inactive at pH 10 and above. The activity reduced to 50% after 15 min at 80A degrees C. Brain heart infusion (BHI) was the best medium for the Bac H27 activity (160 AU/mL). Bac H27 was purified by ammonium sulfate precipitation followed by Q-Sepharose and Sephadex G-75 column chromatographies. Its size was estimated to be 4.9 kDa by Tricine SDSPAGE. Partially purified Bac H27 killed L. monocytogenes ATCC 19111 when added into L. monocytogenes culture. Bac H27 could be useful as a novel food grade preservative inhibiting B. cereus and L. monocytogenes, 2 important food pathogens.