D. SENBAGAM, B. SENTHILKUMAR AND M. RAJASEKARA PANDIAN
Abstract
Bacteriocins, which are protenacious compounds produced by Lactococcus lactis. They inhibit the growth of Gram positive and few Gram negative pathogens involved in food spoilage and they are extended to be used as natural food preservatives. Lactococcus lactis isolated in this study is a nisin producing strain and they were purified using plate count agar enhanced with nalidixic acid and natamycin. In this study modified dairy based medium was used to extract the nisin from the cells. The amount of protein was also estimated and bactericidal activity was studied. The nisin extracted from the isolates can inhibit the organisms such as Staphylococcus aureus, Bacillus cereus and Enterococcus faecalis. For E.coli it showed intermediate result and for Salmonella typhi and Proteus vulgaris, it showed partial lysis (resistant).The nisin was also employed to preserve the eggs in this study. The nisin enhanced the self life of eggs upto 20 days and the eggs without nisin were spoiled at 7t1 day itself. In this study, it was concluded that the nisin obtained from Lactococcus lactis was able to inhibit the growth of some pathogens that are involved in food spoilage. So we can use nisin as a biopreservative for foods.