Characterization of bacteriocins produced by strains from traditional Bulgarian dairy products

As a result of extensive screening of over 300 strains from the Collection of ELBY Bulgaricum, PLC, thirty six strains were selected as producers of bacteriocins, active against closely related lactic acid bacterial species and some food spoilage bacteria. The selected strains belong to L. helveticus, L. bulgaricus and S. thermophilus, which are rare bacteriocin producers. Nineteen nonidentified producers were characterized by molecular taxonomic approaches - M13 fingerprinting, repetitive PCR, ribotyping and hybridization with species-specific probes, which allowed to affiliate them to the species L. delbrueckii. Several strains were found to harbour plasmids of different size. The estimated activity against food borne pathogens makes the isolated substances perspective as safe food preservatives and the producing strains could be used as components of starters with improved quality.