High-cell-density fed-batch processes for bakers' yeast production will involve a low-average-specific growth rate due to the limited oxygen-transfer capacity of industrial bioreactors. The relationship between specific growth rate and fermentative capacity was investigated in aerobic, sucrose-limited fed-batch cultures of an industrial bakers' yeast strain. Using a defined mineral medium, biomass concentrations of 130 g dry weight/L were reproducibly attained. After an initial exponentialfeed phase (Β΅ = 0.18 h -1 ), oxygen-transfer limitation necessitated a gradual decrease of the specific growth rate to ca. 0.01 h -1 . Throughout fed-batch cultivation, sugar metabolism was fully respiratory, with a biomass yield of 0.5 g biomass/g sucrose -1 . Fermentative capacity (assayed off-line as ethanol production rate under anaerobic conditions with excess glucose) showed a strong positive correlation with specific growth rate. The fermentative capacity observed at the end of the process (Β΅ = 0.01 h -1 ) was only half that observed during the exponential-feed phase (Β΅ = 0.18 h -1 ). During fed-batch cultivation, activities of glycolytic enzymes, pyruvate decarboxylase and alcohol dehydrogenase in cell extracts did not exhibit marked changes. This suggests that changes of fermentative capacity during fed-batch cultivation were not primarily caused by regulation of the synthesis of glycolytic enzymes.