Lactobacillus helveticus grown in milk with pH control at 6.2 had a slower growth rate (mu = 0.27 h(-1)) and produced less exopolysaccharide (49 mg l(-1)) but increased lactic acid production (425 mM) compared to cultures without pH control (mu = 0.5 h(-1), 380 mg exopolysaccharide l(-1), and 210 mM lactate), respectively. Both cultures displayed a mixed-acid fermentation with formation of acetate, which is linked not only to citrate metabolism, but also to alternative pathways from pyruvate.