Characterization of a novel bacteriocin produced by Lactobacillus sakei LSJ618 isolated from traditional Chinese fermented radish

A novel bacteriocin, sakacin LSJ618, produced by the strain Lactobacillus sakei LSJ618 isolated from traditional Chinese fermented radish, was studied. L. sakei LSJ618 was identified by both phenotypical and physiological tests combined with 16S rDNA sequence analysis. Sakacin LSJ618 is sensitive to hydrolytic enzymes including lipase, is stable between pH 2–8, and is heat resistant (30 min at 121 °C). Sakacin LSJ618 exhibits inhibitory activity against food-spoiling bacteria and food-borne pathogens, including the Gram-positive Listeria monocytogenes, Staphylococcus aureus, Sarcina sp., Micrococcus luteus, and the Gram-negative Proteus sp. and Escherichia coli, but not against most of the lactic acid bacteria tested. Maximal production of bacteriocin was reached in the late stationary phase, and inhibitory activity declined within 26 h. The mode of action of sakacin LSJ618 was determined to be bactericidal, as evidenced by its action upon Micrococcus tetragenus. After partial purification by ammonium sulfate precipitation and Sephadex G-25 chromatography, the molecular weight of sakacin LSJ618 was determined to be 5.2 kDa by Tricine-SDS-PAGE. The identified properties of sakacin LSJ618 indicate that it is a novel bacteriocin with potential application as a biopreservative in the food industry.