Inhibition of Listeria monocytogenes by Carnobacterium spp. strains in a simulated cold smoked fish system stored at 4 degrees C.

Preservation of smoked salmon from bacterial spoilage, and especially from Listeria monocytogenes by bacteriocin producers is a promising challenge. Over a hundred lactic acid bacteria, isolated from commercial vacuum packaged cold smoked salmon, were screened for their antagonistic activity against L. innocua. Twenty-two strains were able to produce bacteriocin-like proteinaceous substances. These strains were characterized physiologically and biochemically as Carnobacterium strains. Three different groups were determined by pulsed-field gel electrophoresis after Sma I and Apa I DNA digestion. Peptidoglycan hydrolases patterns completed the characterization of these strains. All were confirmed as being Carnobacterium piscicola. Growth and bacteriocin production of three strains of each group and two well known bacteriocin producers (C. divergens V41 and C. piscicola V1) were tested in a simulated cold smoked fish system at 4 degrees C. These strains were able to reach 10(8) cfu ml(-1) in 21 days and to produce as much bacteriocin activities in the cold smoked fish system as in the rich media. Carnobacterium divergens V41 and C. piscicola V1 were the most effective strains in co-culture experiments, inhibiting L. monocytogenes as early as day 4, whereas C. piscicola SF668 inhibiting effect was observed at day 13. The potential for using such biopreservation treatments on whole smoked salmon is discussed.