For batch culture of lactic acid bacteria, seed cultures have to be highly supplemented with complex substrates to obtain an active inoculum. In contrast, for industrial applications, nitrogen supplementation of the fermenter culture must be kept low to minimize costs. Addition of inorganic phosphate, a low cost component, to the medium increased the lactic acid production rate (40% for media supplemented with 2 g dm(-3) yeast extract), but had no effect on growth rate. This effect was absent for high-nitrogen supplemented medium (20 g dm(-3) yeast extract), because of the lack of phosphorus limitation.