A novel bacteriocin produced by Lactobacillus delbrueckii subsp. lactis with a specifically antimicrobial activity against Bacillus cereus

Abstract

Bacteriocins are the ribosomal synthesized antimicrobial peptides used as natural preservatives against pathogens during food production process. The main problem of using bacteriocin and their producers is that these antimicrobials also inhibit the existing flora including non-starter lactic acid bacteria. The question is whether bacteriocins with narrow antimicrobial activity could be a solution? In this study, bacteriocins produced from lactic acid bacteria (LAB) having antimicrobial activity specifically on Bacillus cereus (BC) was isolated and characterized. To select the anti-BC bacteriocin LAB producer, a cocktail including of diverse B. cereus strains was used as indicators. The isolate Yo6B1 obtained from condensed yogurt showed antimicrobial activity against BC at both spot and well diffusion assays. This isolate and its bacteriocin-like metabolite did not inhibit any LAB tested, although it had antimicrobial activity against all BC strains (n=59) isolated from food samples. 16S rDNA sequence of Yo6B1 indicated that it was 99% homolog with the Lactobacillus delbrueckii subsp. lactis. The partial purified Yo6B1 was degraded with proteolytic enzymes including trypsine, α-chmotrypsine, pepsine and proteinase K proved that Yo6B1 was a bacteriocin although the genome of Lb. delbrueckii subsp. lactis did not contain any known bacteriocin production genes. MALDI-ToF analysis indicated that bacteriocin Yo6B1 has a small molecular size. As a conclusion, Lb. delbrueckii subsp. lactis produced a novel narrow spectrum bacteriocin, which has specifically antimicrobial activity against BC. This study also demonstrated that pathogen-specific bacteriocins could be used to eliminate pathogens in foods with no antibacterial effects against LAB microflora.