Lactic acid bacteria have extensively been used in the food industry for many years thanks to their antagonistic activity against other microorganisms. This is because they can produce not only organic acids but also antibacterial bacteriocins and antifungal peptides. The nature of bacteriocin is protein with a killing spectrum against Gram-positive and/or Gram-negative bacteria. In this study, the authors have isolated 69 strains of lactic acid bacteria from Vietnamese traditional fermented cabbages. Among these strains, two strains T8 and T3 have been shown to be capable of producing bacteriocin strongly. Bacteriocin extracts from these two stlains were obtained and studied on the antibacterial spectrum, thermostability, effect of pH and enzymes. The results have indicated that they express their strong antibacterial activities against both Gram-negative and Gram-positive bacteria. They were found to secrete bacteriocins of group I (Lantibiotic), which showed stability in 121°C for 15 min and at pH 4-10. Experimental effects of enzyme on antibiotic activity revealed that the raw bacteriocin was inactivated by a-chymotrypsin, but stable with proteinase K treatment. The bacteriocin extract of the strain T8 was tested for the preservation of fresh cobia meat, which has :shown that the sensory quality, physicochemical change and microbiological counts of the food are well kept at 0-4oC within first seven days. These results also reveal potential applications of bacteriocins as food biopreservatives.
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