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영어

To produce a novel bacteriocin against fish pathogenic bacteria, Lactococcus lactis subsp. was isolated from flounders collected from aquaculture farms. The antimicrobial activity and some physico-chemical properties of the purified bacteriocin were studied. The bacteriocin was purified by 15% PEG 4000/20% Na2SO4 and ethanol saturation followed by twice C-18 reverse phase HPLC. The molecular weight of the bacteriocin measured by MALDI-TOF was 3.3 kDa. We found that the bacteriocin inhibited the growth of gram-positive bacteria including fish pathogenic bacteria, Streptococcus sp. and Lactococcus garviae, but not the growth of gram-negative bacteria. Especially, S. pleomorphus indicator strain (400 arbitrary units ml-1), which is a harmful pathogenic bacteria to aquaculture fish, was shown to be most sensitive . The bacteriocin was found to be stable at 100°C for 20 min and in pH ranged from 3.0-4.0, but it was unstable at pH 10.0. The results indicates that antimicrobial agent produced by L. lactis subsp. may be a good candidate instead of antibiotics to apply in aquaculture and seafood industries.