Antilisterial Mechanism Of Lacticin LLC518Produced By Lactococcus Lactis Subsp. Lactis LLC518

Bacteriocins have the advantages of high activity, non-toxic and protein nature, and it acts as the natural food preservative by inhibiting or killing the pathogenic bacteria and spoilage microorganism in food. In this paper, the antilisterial mechanism of Lacticin LLC518which produced by Lactococcus lactis subsp. lactis LLC518was studied. In hope of obtaining some valuable information which can provide a theoretical basis for its application and development in food preservatives.Lacticin LLC518was purified by40%ammonium sulphate precipitation and Sephadex G-50gel filtration chromatography. The results suggested that the activity of the bacteriocin had been greatly improved after the purification process.The MIC of Lacticin LLC518against Listeria monocytogenes ATCC19115were determined using dilution method. The MIC was defined as the lowest concentration of bacteriocin which prevented cell growth of indicator bacteria in tubes after incubation18-20h at37℃. The effect of Lacticin LLC518on growing cells of L. monocytogenes ATCC19115was studied. The results suggested that the mode of action of Lacticin LLC518(2×MIC) against L. monocytogenes ATCC19115was considered as bactericidal with concomitant cell lysis and its MIC was0.275mg/mLThe effect of different glucose concentrations on sensitive cells of L. monocytogenes ATCC19115was studied. Apparently, Lacticin LLC518may require energized membrane for insertion, and100mmol/L is preferable. The results suggested that the action of Lacticin LLC518was enhanced when target cells were energized.Results from killing assays performed with Lacticin LLC518suggested that the addition of0.275mg/mL of Lacticin LLC518to energized cells of L. monocytogenes ATCC19115lead to efflux of UV-absorbing materials, resulting in a collapse of Acp and ApH.These data indicated that the bacteriocin influences cells by making sensitive cell membranes permeable. Leak-age of intracellular components suggests that the primary effect of the bacteriocin on sensitive cells could be the formation of pores in the plasma membrane and induces the cells death by formed the nonselective pore.