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

Enterococcus faecium 7C5 produces a bacteriocin active against Listeri a monocytogenes and Listeria innocua. In cocultures of the strain 7C5 with a thermophilic starter, which was composed of Streplococcus therm ophilus and Lactobacillus delbrueckii subsp. bulgaricus, the acidifyin g activity of the latter was not affected. In contrast, the rate of ba cteriocin production was lower when compared with the pure culture of strain 7C5. In co-cultures of L. innocua CNRZ LIN11 with the thermophi lic starter or with strain 7C5, a bacteriostatic effect on Listeria gr owth was observed. In the co-culture of L. innocua with both strain 7C 5 and the thermophilic starter, a complete listerial inhibition occurr ed. 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 t he potential of using bacteriocin-producing strains as a culture adjun ct to inhibit Listeria during cheese manufacturing.