Optimization of enterocin P production by batch fermentation of Enterococcus faecium P13 at constant pH

The influence of pH on growth, enterocin P production and glucose consumpti on by Enterococcus faecium P13 was studied during anaerobic batch fermentat ion in MRS broth at 32 degreesC in a fermentor. Growth and glucose consumpt ion were maximal at pH 7.0. Enterocin P production displayed primary metabo lite kinetics and was strongly dependent on pH. A maximum antimicrobial act ivity of 1,949 bacteriocin units (BU) ml(-1) was obtained at pH 6.0, which represented a four-fold increase compared with the antimicrobial activity o btained without pH regulation. The pH exerted a marked effect on the decrea se in bacteriocin activity,with the decrease being maximal at pH 7.0. In th is report, we propose models for the growth of E. faecium P13 as well as en terocin P production and inactivation. Enterocin P production decreased whe n potentially stress-inducing compounds (NaCl or ethanol) were included in the growth medium.