Production of bacteriocins by Enterococcus spp. isolated from traditional, Iranian, raw milk cheeses, and detection of their encoding genes

Strong bacteriocins, or bacteriocins with a wide range of activity against pathogens and spoilage microorganisms, are actively sought for use as natural food preservatives. This work reports the inhibitory activity of 96 enterococcal isolates from two Iranian, raw milk cheeses against five indicator organisms (including Listeria innocua). Forty-eight isolates inhibited at least one indicator in spot agar assays. Of these, 20 isolates corresponding to 15 different strains were shown to produce bacteriocin-like substances in liquid cultures. PCR analysis revealed the genes coding for enterocins (enterococcal bacteriocins) A, B, P or X, or their combinations, in all but one of these 15 strains. In addition, the gene coding for enterocin 31 was detected in two strains. No amplification was obtained in one strain when using specific primers for all 13 bacteriocin genes sought. Three different enterocin genes were identified in most strains and four in one strain. Although the concomitant production of bacteriocins is still to be verified, producers of multiple enterocins could be of great technological potential as protective cultures in the cheese industry.