In a 5-L fermentor (NBS-MF 105), Saccharomyces cerevisiae W303-181 (1.0 g dry matter/L) was inoculated into 3.0 L of liquid medium containing glucose (10 or 20 g/L), yeast nitrogen base (YNB, 3.7 or 7.4 g/L), L-histidine (0.02 g/L), L-tryptophan (0.02 g/L), uracil (0.02 g/L), and adenine (0.02 g/L). The culture was carried out batchwise for 12 or 24 h at 30 degrees C, pH 4.6 or 5.7, aeration of 0, 0.8, 1.7 or 2.2 vvm, and agitation of 400 rpm. The highest G6PDH productivity (10.5 U/L center dot h) and specific activity (320 U/mg of protein) occurred at aeration of 2.2 vvm, pH 5.7, 10 g/L of glucose, and 3.7 g/L of YNB. The G6PDH specific activity attained was comparable with those of commercial preparations, which are between 50 and 600 U/mg of protein.