Plasmid-associated bacteriocin production byLactobacillusLMG21688 suppressesListeria monocytogenesgrowth rebound in a food system

Bacteriocin produced by Lactobacillus curvatus CWBI-B28wt is not completely effective against Listeria monocytogenes in food models. There is evidence suggesting that bacteriocin-degrading proteolytic enzymes produced by the CWBI-B28wt strain and/or present in the food matrix contribute to this rebound of Listeria growth. To limit this problem, we have partially characterized an approximately 10-kb plasmid responsible for bacteriocin production in L. curvatus CWBI-B28wt. This plasmid was transferred by high-voltage electroporation into a less proteolytic, but technologically competent Lactobacillus strain. When the transformed strain was used as a starter culture in a model food system, a high bacteriocin level was maintained for a longer time than with CWBI-B28wt, and Listeria growth rebound was delayed by 2 weeks (occurring after 3 weeks of apparently total inhibition, instead of one).