Inhibitory Activity of Three Lactic Acid Bacteria Strains: Bacteriocin Production ^†

Abstract

Background: The bacteriocins from lactic acid bacteria (LAB) are candidates for applications such as biopreservation of food. Due to their potential as alternatives to antibiotics, their antimicrobial activities against pathogenic and spoilage bacteria are of great research interest. The enterocins, which are produced by the Enterococcus species have been widely studied; they are recognized as probiotics by several researchers [1]. In the present study, we explore three LAB strains: Enterococcus sp. CM9, Enterococcus sp. CM18, and Enterococcus sp. H3 that produce bacteriocins named enterocins CM9, enterocins CM18, and enterocins H3, respectively [2]. Method: For the antimicrobial test, fifteen pathogenic bacteria were tested by the spot agar [3] and the well diffusion assays [4]. For the characterization of enterocins, the effect of pH, heat, and chemical agents on the activity of enterocins was evaluated by the well diffusion assay [5]. Results: The LAB used in the present work showed inhibitory activity against all pathogenic bacteria tested, while the supernatant of LAB exhibited inhibitory activity against L. monocytogenes, E. coli and S. Typhimirium. The enterocins produced by the three LABs appeared stable to adjustment of an acidic or basic pH. They were resistant to the temperature until 121 °C for 15 min, therefore demonstrating their thermostability. Excepting the triton X100, they remained stable after treatment with between 20 and 80, NaCl, SDS, urea, and EDTA. Conclusion: The results indicate that the enterocins CM9 and CM18 belong to class IIa bacteriocins and experimentation will be required for their application.