Enzymatic hydrolysis of corn starch after extraction of corn oil with ethanol

To develop a yeast strain that is able to produce ethanol directly from starch, α-amylase cDNA (originated from mouse salivary glands) was introduced into the hyploidSaccharomyces diastiticus cells secreting glucoamylase by using a linearized integrating vector. The integrating vector contains aLEU2 gene and the inside of theLEU2 gene was cut byKpnl to make the linearized vector. One of the transformants exhibited 100% mitotic stability after 100 generations of cell multiplication. To improve its ethanol-fermentability, the haploid transformant was rare-mated with a polyploid industrial strain having no amylase activity. The resulting hybrid RH51 produced 7.5 (w/v) ethanol directly from 20% (w/v) soluble starch and its mitotic stability was 100% at the end of fermentation.