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Efficacy of Bacteriocins Produced by Lactic Acid Bacteria as Biological Food Preservative


Investigations were made to screen Lactic Acid Bacteria (LAB) for bacteriocin production and to test the efficacy of Bac+ LAB and /or bacteriocins as a barrier against the growth and multiplication of psychrophilic pathogens in fish based model meat system at low temperature conditions. Bacteriocin activity was detected early in the logarithmic phase and increased up to late logarithmic phase of growth of Lactobacillus plantarum 8014 and Pediococcus pentosaceus 25445 in MRS broth. A maximum bacteriocin activity of 400 AU/ml was observed when grown in MRS broth. The partially purified bacteriocin fraction of L. plantarum 8014 and P.  pentosaceus 25445 had an activity of 6400 AU/ml and 3200 AU/ml respectively. Bacteriocins were found to be sensitive to proteolytic enzymes, resistant to heat and identified as relatively high molecular weight protein aggregate by SDS-PAGE. They exhibited anti-microbial action against several food spoilage and food-borne pathogens   including   Aeromonas hydrophila,   Vibrio cholerae, V.parahaemolyticus, Staphylococcus aureus, E. coli, Salmonella spp., Shigella spp. and Pseudomonas spp. About 40-56 % of fish isolates tested were inhibited by bacteriocins. Production of bacteriocin during fermentation of trash fish was also observed. The growth of S. aureus was inhibited by Bac+ LAB cells and not by cell free supernatant at 4 oC. A ten fold reduction in A. hydrophila count was observed in glucose supplemented meat inoculated with P.  pentosaceus 25445.  A non-specific inhibition of S. aureus and A. hydrophila, to some extent, was observed in meat system without glucose.