Production of ethanol by direct fermentation of soluble starch was carried out using a derepressed mutant M-6 of Schwanniomyces castellii NRRL Y-2477. Under optimal fermentation conditions, 58.4g/l ethanol was produced utilizing 86% of 150g/l soluble starch. With a mixed culture of mutant M-6 and Saccharomyces cerevisiae STV 89, 64.3g/l of ethanol was produced utilizing 94% of 150g/l soluble starch.