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 co-cultures of the strain 7C5 with a thermophilic starter, which was composed of Streptococcus 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 LIN 11 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°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.