Construction of a brewing yeast having glucoamylase activity and its fermentation characteristics.

The brewing yeast having glucoamylase activity was constructed by integrating glucoamylase cDNA from Asapergillus niger into the genome of brewing yeast B48. The integration was achieved by cotransformation of YEP type plasmid pKG1 carrying glucoamylase expression-secretion element and was verified by Southern blot analysis. The engineered yeast was stable, and the fermentation test demonstrated that the lower residual dextrin level was obtained compared with control strain B48. Thus the fermentation rate was raised to 80.5%. No alteration of growth and brewing properties was observed. Beer quality was judged to be good.