40 C, an ethanol concentration of 6.88% (w/v) was obtained in a medium containing 22% sugars at the same fermentation time as at 37 C. However, the highest productivity (1.42 g/l/h), and yield (72.6% of theoretical yield) were attained with a medium containing 16% sugars at 40 C. The effect of (NH4)2SO4 as a nitrogen source at a concentration of 0–0.1% on ethanol fermentation of DMKU 3-1042 was determined in a sugar cane juice medium composed of sugar cane juice supplemented with sucrose to 22% total sugars and adjusted to pH 4.5. At 37 C, the highest ethanol concentration, 7.8% (w/v), was obtained with 0.07% (NH4)2SO4 supplementation (Table 2); the productivity was 1.08 g/l/h and the yield was the highest: 69.5% of theoretical yield. However, the highest productivity, 1.36 g/l/l, was attained when the medium was supplemented with 0.05% (NH4)2SO4; the maximal ethanol concentration was 7.35% (w/v) and the yield was 65.5% of theoretical yield. In sugar cane juice media without supplementation with a nitrogen source, the ethanol concentration (6.85% w/v), productivity (0.95 g/l/h) and ethanol yield (61.0% of theoretical yield) observed were lower. At 40 C, the ethanol concentrations between 6.22–6.66% (w/v) were obtained in the medium without and with supplementation with a nitrogen source at various concentrations; these concentrations were significantly lower than those obtained at 37 C. The productivity in the medium supplemented with 0.05% (NH4)2SO4 was 1.37 g/l/h, which was the highest among all treatments, while in the medium without nitrogen supplementation, productivity was only 1.15 g/l/h; in media supplemented with 0.07% and 0.1% (NH4)2SO4, the productivities were 1.05 and 1.07 g/l/h, respectively. Fermentation yield obtained in media with and without supplementation with a nitrogen source were in the range of 55.4–58.8% of theoretical yield. Hence, (NH4)2SO4 at 0.05% was chosen for further study since it provided the highest productivity at both temperatures with not much difference in maximal ethanol concentrations and yields. The effect of a potassium source was studied using KH2PO4 at 0–0.10% added to a sugar cane juice medium composed of sugar cane juice supplemented with sucrose to 22% total sugars and 0.05% (NH4)2SO4 and having a pH of 4.5. At 37 C, the highest ethanol concentration, productivity and yield: 7.65% (w/v), 1.06 g/l/h and 68.1% of theoretical yield, respectively, were attained by fermentation in a medium supplemented with 0.05% KH2PO4. In contrast, at 40 C, there was little difference in ethanol Table