摘要：Bacteriocins are biologically active proteins or protein complexes that display a bactericidal mode of action towards usually closely related species. Bacteriocin producing Lactococcus lactis AP2 was isolated from fermented milk products (dahi, lassi etc.) from the different regions of Solan district of Himachal Pradesh, India. The strain was selected and screened for their ability to produce bacteriocin by agar well diffusion method using the supernatant of centrifuged test culture. The bacteriocin had wide spectrum of inhibitory activity against test strains of pathogenic and food spoilage micro organisms. The cell-free supernatant of Lactococcus lactis AP2 inhibited the growth of Escherechia coli, Pseudomonas aeruginosa, Shigella dysenteries, Stapyhlococcus aureus and Bacillus cereus. The bacteriocin of Lactococcus lactis AP2 was recovered at 30-40 % ammonium sulphate saturation level and the protein was 0.10 mg/ml. Purified bacteriocin was found to possess a molecular weight of 12 kDa. The bacteriocin from the organism viz. Lactococcus lactis AP2 is stable at low temperature (up to 72h) and at acidic pH 2 to 6 thereby rendering it to be used in acidic foods as biopreservative. Biopreservative effect of bacteriocin i.e. purified bacteriocin expressed better results as compared to chemical preservative i.e. sodium benzoate used for the preservation of acidic food items viz. orange and mixed fruit juice.
