Effect of enterocin CCM 4231 on Listeria monocytogenes in Saint-Paulin cheese.

The bacteriocin production by Enterococcus faecium strain in cheese milk and cheese was demonstrated. Purified enterocin CCM 4231 exhibited an anti-listerial effect during Saint-Paulin cheese manufacture. During cheese production the strain grew to a final concentration of 10.1 +/- 0.01 log CFU per mL per g in cheese. Then only a slight decrease of the cell concentration was noticed during ripening and was almost stable for 8 weeks. No significant differences in pH were observed between the experimental and reference cheeses. Bacteriocin production during cheese manufacture was detected only in milk samples and curd, reaching a level of 100 AU/mL. After addition of purified enterocin CCM 4231 (concentration 3200 AU/mL) into the experimental cheese, the initial concentration of 6.7 +/- 0.06 log CFU per mL of Listeria monocytogenes Ohio was reduced up to 1.9 +/- 0.01 log CFU per mL per g. After 6 weeks and at the end of the experiment the difference of surviving cells of L. monocytogenes Ohio in ECH was only one or 0.7 log cycle compared to the control cheese. Although enterocin CCM 4231 partially inhibited L. monocytogenes in Saint-Paulin cheese manufacture, an inhibitory effect of enterocin added was shown in 1-week cheese; however, it was not possible to detect bacteriocin activity by the agar spot test. The traditional fermentation and ripening process was not disturbed, resulting in acceptable end-products, including sensory aspects.