Joint action of a dextrinogenic amylase, a glucose-producing amylase and transglucosidase upon starch in the presence or absence of yeast

Abstract Curves of fermentable sugar production in the secondary phase of starch hydrolysis with joint systems of a crystalline dextrinogenic amylase, a highly purified glucose-producing amylase, and a partially purified transglucosidase, in the presence and absence of yeast, were observed. In the absence of yeast, the higher the ratio of dextrinogenic amylase to glucose-producing amylase, the more maltose was formed and more marked was the effect of the action of transglucosidase. In the presence of yeast, the effect of transglucosidase in decreasing the rate of secondary conversion was not observed, and a renewed rather rapid hydrolysis of the residual substrate took place. This fact was concluded, according to Pan et al., to be a result of the reconversion of presynthesized unfermentable oligosaccharides into fermentable sugars by the reversible action of transglucosidase after the removal of maltose by yeast. Further, it was concluded that the amount of glucose-producing amylase determines the rate of secondary fermentation and that the dextrinogenic amylase is indispensable as a complement of glucose-producing amylase although its activity need not be high unless a high concentration of viscous starch is used as the substrate.