Park, C.S., Park, Y.J., Lee, Y.H., Park, K.J., Kang, H.S. and Pek, U.H.

Abstract
The production of a new brewing yeast strain by transformation with a recombinant plasmid featuring the STA1 glucoamylase gene from Saccharomyces diastaticus (modified by replacing its promoter region with that of the alcohol dehydrogenase isoenzyme 1 gene, in order to enhance its expression level), plus the CUP1 gene as a selection marker, is described. A number of different plasmids were obtained or constructed, the most successful being a multiple integration plasmid designated YCp50CSRII, using ribosomal DNA as a homologous recombination sequence. The resulting yeast remained stable over 70 generations. Brewing trials showed that, as a result of increased enzymatic activity, beer fermented by this strain had a significantly lower carbohydrate content and higher alcoholic strength than that fermented by an equivalent conventional strain from identical wort, but was otherwise very similar and of equally acceptable quality.
Keywords : brewers' yeast DNA plasmid enzymic activity fermentation gene expression recombination transformation yeast strain