The effect of pH on growth and lactic acid prodn. of L. helveticus was investigated in a continuous culture using supplemented whey ultrafiltrate. Max. lactate productivity of 5 g/L/h occurred at pH 5.5. Whey permeates concd. up to 4 times were fermented using batch cultures. Max. lactic acid concn. of 95 g/L was attained, but residual sugars indicated a possible limitation in growth factors. [on SciFinder (R)]