INHIBITORY ACTIVITY OF THREE LACTIC ACID BACTERIA STRAINS: BACTERIOCIN PRODUCTION

Background: The bacteriocins produced by lactic acid bacteria (LAB) are candidates for application as food biopreservatives and as an alternative of antibiotics. The antimicrobial activities against pathogenic and spoilage bacteria are one of the properties of bacteriocins.

In the present study, the bacteriocins produced by three strains of LAB were studied and characterized: enterocins CM9 (Enterococcus sp CM9), enterocins CM18 (Enterococcus sp CM18) and enterocins H3 (Enterococcus sp H3).

Method: A number of fifteen of different pathogenic bacteria was tested for antimicrobial activity. The spot agar and well diffusion methods were used. The well diffusion method was also used for the characterization of enterocins, by studying the effect of pH, heat and chemical agents on the activity of enterocins.

Results: The LAB used in the present work, showed an inhibitory activity against all pathogenic bacteria tested. The supernatant of LAB exhibited an inhibitory activity against Listeria monocytogenes, Escherichia coli and Salmonella Typhimirium. The enterocins produced by the three strains of LAB appeared stable to adjustment of pH and were resistant to heat, showing their thermostability. Excepting the Triton X100, they remained stable after treatment with Tween 20 and 80, NaCl, SDS, urea and EDTA.

Conclusion: The results indicate that the enterocins CM9 and CM18 belong to class IIa bacteriocin and present a wide inhibitory spectrum. The biological properties of the three strains of LAB suggest that these strains merit further investigations so they can be applied in public and veterinary health programs.