A batch culture of Saccharomyces cerevisiae for the production of hexokinase was carried out in a 5-L fermenter containing 3 L of culture medium, which was inoculated with cell suspension (about 0.7 g/L), and left fermenting at 35 degreesC and pH 4.0. The aeration and agitation were adjusted to attain k(L)a values of 15, 60, 135, and 230 h(-1). The highest hexokinase productivity (754.6 U/[L .h]) and substrate-cell conversion yield (0.21 g/g) occurred for a k(L)a of 60 h(-1). Moreover, the formation of hexokinase and cell growth are coupled events, which is in accordance with the constitutive character of this enzyme. Hexokinase formation for k(L)a > 60 h(-1) was not enhanced probably owing to saturation of the respiratory pathway by oxygen.