Enterocin HZ produced by a wild Enterococcus faecium strain isolated from a traditional, starter-free pickled cheese

Bacteriogenic Enterococcus faecium HZ was identified by using biochemical (Strep-API 20, API-50 CHL, fatty acid profile) and 16S rRNA analysis (99 center dot 99%). Ent. faecium HZ was sensitive to clinically important antibiotics such as vancomycin, and did not have gelatinase and haemolysis activities. Enterocin HZ, a bacteriocin from Ent. faecium HZ, was sensitive to papain and tyripsin, but resistant to pepsin, lipase, catalase, alpha-amylase, organic solvents, detergents, ss-mercaptoethanol, and heat treatment (90 degrees C/30min). It was biologically active at pH 2 center dot 0-9 center dot 0 and synthesised at the highest level in MRS or M17 broth at 32 or 37 degrees C with an inoculum amount of 0 center dot 1-0 center dot 5% and an initial pH of 6 center dot 0-7 center dot 0. Enterocin HZ production reached maximum level at middle and late logarithmic phase and its molecular weight was similar to 4 center dot 5kDa. It was active against some Gram-positive foodborne bacteria. Ent. faecium HZ or its bacteriocin enterocin HZ is a good candidate to be studied as a food biopreservative since enterocin HZ showed strong bactericidal activity against Listeria monocytogenes in UHT milk and also Ent. faecium HZ grew very well in milk and produced enterocin HZ at maximum level.