High-concentration ethanol production from cooked corn starch by using medium-temperature cooking process.

An improved process for high-concentration ethanol production from cooked corn starch by Saccharomyces sp. W4 has been well developed. Simultaneous cooking and liquefaction of corn starch were performed by using thermophilic alpha-amylase at 95 degrees to 105 degrees C. The mash was then saccharified at 60 degrees C by using high-efficiency glucoamylase. Saccharomyces sp. W4 could produce 18.3% (v/v) ethanol at 30 degrees C within 60 hrs, with 1.2% reducing sugar and 4.1% total sugar remaining in the fermented mash. It was found that ammonium sulfate could accelerate the fermentation rate. When 0.9 g of ammonium sulfate was added to 280 mL of the fermentation media, 18.9% (v/v) ethanol could be reached in the mash after 50 hrs of fermentation, leaving 0.27% reducing sugar and 3.1% total sugar in the fermented media.