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.