INHIBITION OF LISTERIA-INNOCUA IN MILK BY BACTERIOCIN-PRODUCING ENTEROCOCCUS-FAECIUM 7C5

Enterococcus faecium 7C5 produces a bacteriocin active against Listeria monocytogenes and Listeria innocua. In cocultures of the strain 7C5 with a thermophilic starter, which was composed of Streplococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus, the acidifying activity of the latter was not affected. In contrast, the rate of bacteriocin production was lower when compared with the pure culture of strain 7C5. In co-cultures of L. innocua CNRZ LIN11 with the thermophilic starter or with strain 7C5, a bacteriostatic effect on Listeria growth was observed. In the co-culture of L. innocua with both strain 7C5 and the thermophilic starter, a complete listerial inhibition occurred. The combined inhibitory effect of the pH decrease and bacteriocin production, which were shown to be synergistic, was demonstrated both at 37 degrees C and under temperature conditions reproducing the first 24 h of a soft-cheese technology. This data substantially supported the potential of using bacteriocin-producing strains as a culture adjunct to inhibit Listeria during cheese manufacturing.