Bacteriocin production by Enterococcus faecium RZS C5 is cell density limited and occurs in the very early growth phase.

Enterocins, bacteriocins produced by enterococci, are gaining interest because of their antilisterial activity. Enterococcus faecium RZS C5, a natural isolate from cheese, produces such a bacteriocin. Generally, bacteriocin production by lactic acid bacteria is a growth-associated process which ceases when cell growth starts to level off. Remarkably, enterocin production by Ent. faecium RZS C5 seems to be limited to the very early growth phase and is switched off at a well-defined cell density of 0.4 g cell dry mass (CDM) l(-1). However, at pH values higher than 6.5, enterocin production displays distinct kinetics. At such pH values, enterocin production is reduced but is maintained until the end of the active growth phase. The relation with cell concentration suggests that enterocin production is part of a severely regulated mechanism. A kinetic model is set up for the description of the early enterocin activity peak. Furthermore, the influence of pH and temperature on the kinetics of growth and bacteriocin production of Ent. faecium RZS C5 was investigated. At pH 6.5, high enterocin activity was obtained in the temperature range 20-35 degrees C. At 35 degrees C, enterocin activity could only be detected between pH 5.5 and 8.0.