Selective control of lactobacilli in kimchi with nisin

The use of nisin to control the lactobacilli responsible for the over-ripening of kimchi, traditional Korean fermented vegetables, was studied. Of the 40 strains of lactic acid bacteria studied, most were sensitive to nisin at a concentration of 100 IU ml-1, while two strains appeared to be resistant. In MRS broth containing nisin at concentrations of 100-300 IU ml-1, the growth of sensitive strains of Lactobacillus plantarum was delayed for 2-3 d at 20 degrees C. When nisin was added to kimchi at a concentration of 100 IU ml-1, the growth of Lactobacillus spp. was inhibited more than the growth of Leuconostoc spp. Scanning electron micrograph observations confirmed the results, demonstrating the predominance of cocci in kimchi containing nisin. These results suggest that at recommended levels, nisin can be used to preserve kimchi by inhibiting lactobacilli more effectively than other lactic acid bacteria involved in kimchi fermentation.