|
Sixty isolates of lactic acid bacteria found in kimchi, a traditional Korean dish of fermented vegetables, were tested for nisin sensitivity. Of the sixty isolates, all belonging to the genera Leuconostoc, Lactobacillus, and Pediococcus, fifty isolates were sensitive to nisin at a concentration of 100 IU/㎖, and four isolates appeared to be resistant to nisin. This demonstrated that the nisin sensitivity of lactic acid bacteria found in kimchi varied considerably among isolates. In MRS broth containing nisin at concentrations of 100 to 300 IU/㎖, the growth of sensitive isolates of Leuconostoc mesenteroides and Lactobacillus plantarum was inhibited for two to three days at 20℃. When nisin was added to kimchi preparations at a concentration of 100 IU/㎖, the growth of lactic acid bacteria was delayed and reached a maximum two days later than that in kimchi without nisin. These results suggest the possible use of nisin in kimchi preparation, at recommended levels, to control the lactic acid fermentation. Scanning electron micrographs of a sensitive isolate L. plantarum revealed the formation of pores on cell surfaces followed by rapid cell wall destruction 1 h after the addition of nisin.
|