Short CommunicationA study on the bactericidal effect of nisin purified from Lactococcus lactis

Abstract

Nisin, the best known LAB (Lactic Acid Bacteria) bacteriocin, is a promising alternative to antibiotics, and displays a broad spectrum of activity against a wide range of spoilage and pathogenic Gram positive bacteria. The aim of the study was to determine the bactericidal effect of nisin. The Lactococcus lactis MTCC 440 used for the study was obtained from IMTECH, Chandigarh. The nisin was purified by ammonium sulphate precipitation and dialysis. It was found that the addition of nisin showed bactericidal activity against Staphylococcus aureus, Micrococcus luteus and Bacillus cereus at 11μgm/10μL, 07μgm/10μL and 08μgm/10μL, respectively. The bactericidal effect of nisin against susceptible test strains showed minimum inhibitory concentrations of 50, 80 and 70 μgm/mL against Staphylococcus aureus, Micrococcus luteus and Bacillus cereus, respectively in MIC test. The molecular weight of nisin was characterized using SDS PAGE and it was found to be 3000 and 7000 Daltons. The study revealed that nisin exhibited bactericidal effect against some of the selected food-borne pathogens and hence can be effectively used in any food product to control either the Gram positive food-borne pathogens or spoilage bacteria.

Keywords/phrases: Bactericidal, Lactococcus lactis, Nisin, Test strains

Ethiop. J. Biol. Sci., 10(1): 95-102, 2011