Inactivation of Gram-positive pathogens in milk by lactic acid bacteria bacteriocins in combination with the lactoperoxidase system

The inhibitory activity of different bacteriocins from lactic acid bacteria (LAB) in combination with the lactoperoxidasethiocyanate-hydrogen peroxide system (LPS) against Listeria monocytogenes and Staphylococcus aureus was investigated in milk. A strong synergistic bactericidal activity of the LPS in combination with nisin or enterocin AS-48 against L. monocytogenes in milk was observed, which resulted in more than 8 log units reductions with respect to the control milk after 24 h at 37°C Less pronounced synergistic effects against this pathogen were observed for the combinations of the LPS with enterocin I or TAB 7. Staphylococcus, aureus was more resistant than L. monocytogenes to the biopreservatives added individually or in combination. Nisin was the only bacteriocin able to reduce the counts of S. aureus. The highest rate of inactivation for this pathogen was achieved in milk with nisin and the LPS. The combination of selected LAB bacteriocins with the LPS might be usefull in controlling undesirable pathogenic microorganisms potentially present milk before or during the manufacture and storage of dairy products.