Listeria monocytogenes (L. monocytogenes) is one of gram-positive foodborne pathogens with a very high fatality rate. Unlike most foodborne pathogens, L. monocytogenes is capable of growing at low temperatures, such as in refrigerated foods. Thus, various physical and chemical prevention methods are used in the manufacturing, processing and distribution of food. However, there are limitations to the methods such as possible changes to the food quality and the consumer awareness of synthetic preservatives. Thus, the aim of this study was to evaluate the anti-listeria activity of lactic acid bacteria (LAB) isolated from kimchi and characterize the bacteriocin produced by Lactococcus lactis which is one of isolated strains from kimchi. The analysis on the anti-listeria activity of a total of 36 species (Lactobacillus, Weissella, Lactobacillus, and Lactococcus) isolated from kimchi by the agar overlay method revealed that L. lactis NJ 1-10 and NJ 1-16 had the highest anti-listeria activity. For quantitatively analysis on the anti-listeria activity, NJ 1-10 and NJ 1-16 were co-cultured with L. monocytogenes in Brain Heat Infusion (BHI) broth, respectively. As a result, L. monocytogenes was reduced by 3.0 log CFU/mL in 20 h, lowering the number of bacteria to below the detection limit. Both LAB strains showed anti-listeria activity against 24 serotypes of L. monocytogenes, although the sizes of clear zone was slightly different. No clear zone was observed when the supernatants of both LAB cultures were treated with proteinase- K, indicating that their anti-listerial activities might be due to the production of bacteriocins. Heat stability of the partially purified bacteriocins of NJ 1-10 and NJ 1-16 was relatively stable at 60oC and 80oC. Yet, their anti-listeria activities were completely lost by 60 min of treatment at 100oC and 15 min of treatment at 121oC. The analysis on the pH stability showed that their anti-listeria activities were the most stable at pH 4.01, and decreased with the increasing pH value, yet, was not completely lost. Partially purified bacteriocins showed relatively stable anti-listeria activities in acetone, ethanol, and methanol, but their activities were reduced after chloroform treatment, yet was not completely lost. Conclusively, this study revealed that the bacteriocins produced by NJ 1-10 and NJ 1-16 effectively reduced L. monocytogenes, and that they were relatively stable against heat, pH, and organic solvents, therefore implying their potential as a natural antibacterial substance for controlling L. monocytogenes in food.

ABSTRACT
Materials and Methods
    사용균주 및 배양
    LAB의 항리스테리아 활성 스크리닝
    BHI에서의 정량적 분석
    항균 스펙트럼 조사
    박테리오신의 부분정제
    박테리오신 검출 및 활성 확인
    박테리오신 안정성 조사
    통계분석
Results and Discussion
    LAB의 항리스테리아 활성 스크리닝
    BHI에서의 정량적 분석
    항균 스펙트럼 조사
    박테리오신의 검출 및 활성 확인
    박테리오신 안정성 조사
Acknowledgement
국문요약
Conflict of interests
ORCID
References

• 손나연(한국교통대학교) | Na-Yeon Son (Department of Food Science and Technology, Korea National University of Transportation, Jeungpyeong, Korea)
• 김태운(세계김치연구소) | Tae-Woon Kim (Technology Innovation Research Division, World Institute of Kimchi, Gwangju, Korea)
• 육현균(한국교통대학교) | Hyun-Gyun Yuk (Department of Food Science and Technology, Korea National University of Transportation, Jeungpyeong, Korea) Corresponding author