Antimicrobial activity and partial characterization of bacteriocins produced by lactobacilli isolated from Sturgeon fish

The antimicrobial spectrum and physico-chemical characteristics of bacteriocin like inhibitory substances produced by lactobacilli isolated from the intestinal flora of Sturgeon fish were determined in order to evaluate their inhibitory potential exerted against 42 food-borne and aquaculture-related bacterial pathogens as well as against food spoilage causing bacteria. In a first series a collection of 84 Lactobacillus strains previously isolated from Beluga (Huso huso) and Persian sturgeon (Acipenser persicus) were screened for their inhibitory activities and potential bacteriocin production against two indicator strains, Listeria monocytogenes ATCC 19115 and Salmonella enterica subsp. enterica serovar Typhimurium ATCC 14028. The isolates Lactobacillus casei AP8 and Lactobacillus plantarum H5 showed the highest activity and therefore were subjected to further examination to clarify the nature of the inhibitory effect. The physico-chemical properties of the harvested antimicrobial compounds were similar to those of bacteriocins of lactobacilli belonging to the group II with respect to molecular weight (5 and 3 kDa respectively), pronounced temperature stability (−20 °C to 120 °C), pH tolerance (3–12), chemical stability (SDS, EDTA, Tween 20, Tween 80) and sensitivity to proteolytic enzymes. Importantly, different food borne pathogens like Escherichia coli, Listeria spp., Salmonella spp., Staphylococcus aureus, Aeromonas hydrophila, Vibrio anguillarum, and Bacillus cereus were inhibited by cell-free supernatants of the strains selected. The broad inhibitory spectrum, the technological properties, especially the stability may lead to the assumption that the bacteriocins like inhibitory AP8 and H5 may be applied as biopreservative agents to control pathogens and spoiling bacteria in different food products. Furthermore their role as bioprotective agents in aquaculture systems is envisaged.