ABSTRACT
When starchy materials were used for alcohol production by fermentation, the starch had to be hydrolyzed to fermentable sugars by amylolytic enzymes before the fermentation process. To obtain a good alcohol yield, the mashes of starchy raw materials usually had to cook at a high temperature. This chapter summarizes our studies for improving and evaluation of recombinant amylolytic yeasts. Some glucoamylase genes from fungi and yeasts have been sequenced. The chapter proposes that the Rhizopus glucoamylase consisted of two functionally distinct domains: one was responsible for adsorption to the starch at the NH2-terminal portion and, another, on the COOH-terminal portion (135-604; catalytic domain), was responsible for starch degradation. It shows that the strain G-2315 displayed slightly reduced growth because it harbored an excess amount of the highly expressed glucoamylase gene. Some glucoamylase genes have been cloned and expressed by yeasts.
