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pork meat, Bacteriocin, Listeria monocytogenes, lactic acid bacteria, and organic acids and salts

Includes references
Avoiding the presence of Listeria in meat and dairy products is a major challenge for the food industry. In this work, a Lactobacillus curvatus strain producing the bacteriocin sakacin P and a Pediococcus acidilactici strain producing another bacteriocin, pediocin AcH, were used as starter cultures under laboratory conditions in a Listeria-seeded raw-pork-meat matrix, which was then stored for 6 weeks at 4 °C. At 1 week intervals during the storage period, the antilisterial activity was evaluated. When either strain was added alone, the Listeria monocytogenes cfu count initially dropped from 10² cfu g⁻¹ to an undetectable level by the end of week 1 or 2, but this was followed by a rebound (regrowth) 1 week later. When both strains were added together to the meat matrix, rebound was delayed, Listeria remaining undetected from the end of week 1 to the end of week 5. A rebound was observed 6 weeks post-inoculation, but fewer than 10 cfu g⁻¹ were counted. The use of more than one bacteriocin-producing strain may thus overcome some of the problems limiting the effectiveness of bacteriocins in food systems.

electrotransformation, PCR amplification, Listeria monocytogenes, plasmid curing, Lactobacillus curvatus, and bacteriocins

Includes references
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).