The novel genetic manipulation to improve the plasmid stability and enzyme activity in the recombinant brewing yeast.

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