In vitro inhibition of microbial flora of fish by nisin and lactoperoxidase system

Aims: To test the antimicrobial effects of nisin and lactoperoxidase system (LP system) against sardines flora. This study is part of a programme designed to investigate the preservability of fish using these inhibitors as potential biopreservatives. Methods and Results: Antimicrobial effects of nisin and LP system alone or in combination were tested by the agar diffusion method against bacterial strains isolated from sardines (Sardina pilchardus). Nisin inhibited only Gram-positive bacteria, whereas LP system inhibited all strains studied. The combination of nisin (100 IU ml(-1)) and LP system (10 level) was significantly more effective than LP system or nisin alone against all strains, excepting Aeromonas salmonicida subsp. salmonicida and Vibrio alginolyticus. Conclusion: These results clearly demonstrated the efficiency of LP System-nisin combination for inhibiting spoilage flora of fish. Significance and Impact of the Study: Because LP system has a broad activity spectrum, it may be an interesting additional hurdle to improve the safety of food preservation by nisin. Combination of nisin and LP system could be of great interest as biopreservatives for fish and fish products.