The influence of pH on growth, enterocin P production and glucose consumption by Enterococcus faecium P13 was studied during anaerobic batch fermentation in MRS broth at 32 degreesC in a fermentor. Growth and glucose consumption were maximal at pH 7.0. Enterocin P production displayed primary metabolite kinetics and was strongly dependent on pH. A maximum antimicrobial activity 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 obtained without pH regulation. The pH exerted a marked effect on the decrease in bacteriocin activity,with the decrease being maximal at pH 7.0. In this report, we propose models for the growth of E. faecium P13 as well as enterocin P production and inactivation. Enterocin P production decreased when potentially stress-inducing compounds (NaCl or ethanol) were included in the growth medium.