Raw starch fermentation to ethanol by an industrial distiller's yeast strain of Saccharomyces cerevisiae expressing glucoamylase and α-amylase genes

Industrial strains of a polyploid, distiller's Saccharomyces cerevisiae that produces glucoamylase and alpha-amylase was used for the direct fermentation of raw starch to ethanol. Strains contained either Aspergillus awamori glucoamylase gene (GA1), Debaryomyces occidentalis glucoamylase gene (GAM1) or D. occidentalis alpha-amylase gene (AMY), singly or in combination, integrated into their chromosomes. The strain expressing both GA1 and AMY generated 10.3% (v/v) ethanol (80.9 g l(-1)) from 20% (w/v) raw corn starch after 6 days of fermentation, and decreased the raw starch content to 21% of the initial concentration.