BACTERIOCIN-LIKE ACTIVITY FROM WEISSELLA CONFUSA AND PEDIOCOCCUS ACIDILACTICI ISOLATED FROM TRADITIONAL THAI FERMENTED SAUSAGES

Bacteriocin-like activity (BLA) was screened in 133 strains of lactic acid bacteria (LAB) isolated from traditional Thai fermented sausages. The inhibition assay against the test organisms showed that eight out of 133 isolates (CP1-15, CP2-11, CP3-1, CP7-3, CP10-3, CP11-6, CP14-1 and CP14-4) suppressed the growth of Bacillus cereus and four (CP1-15, CP7-3, CP14-2 and CP14-3) suppressed the growth of Staphylococcus aureus but none could suppress the growth of Escherichia coli and Salmonella sp. The isolates with the highest activity against the two Gram positive test strains (CP3-1 for B. cereus and CP7-3 for S. aureus) were further investigated for the effect of heat treatment at different pH values and for combined effects of dual mixtures. The increase in heating temperature (between 65 and 100 °C) and time (between 5 and 60 min) significantly decreased BLA, while the changes in pH (between 4 and 6) had little effect. When the filtrates of the two isolates were mixed, BLA seemed to be synergistic against each test strain. Regression equations were obtained by fitting the experimental percent inhibition data with second-order polynomial equations. The simulated data agreed well with the experimental data within 10 % when the filtrates were incubated at 65 °C for 5, 15, 30 and 60 min and at 80 °C for 5, 15 and 30 min. The isolates CP3-1 and CP7-3, which had an antagonistic effect against the two strains of Gram positive foodborne bacteria, were formerly identified as Weissella confusa and Pediococcus acidilactici, respectively. It is the researcher’s belief that this is the first report on BLA from W. confusa against B. cereus.

Keywords
lactic acid bacteria, bacteriocin, antibacterial activity, inhibitory activity, Weissella confusa, Pediococcus acidilactici