[Construction of a new brewing yeast strain with secretive alpha-amylase activity and reduced diacetyl production].
摘要
Saccharomycopsis fibuligera possesses high alpha-amylase and glucoamylase activities that enable it to utilize raw starch as a carbon source. A expression cassette containing the promoter sequence of 3-phosphogylycerate kinase gene (PGK1p), the alpha factor signal sequence from Saccharomyces cerevisiae and the alpha-amylase coding sequence of S. fibuligera was constructed. The alpha-amylase expression cassette was inserted in the ILV2 locus of industrial brewer's yeast strain YSF-5 encoding alpha-acetolactate synthase (AHAS) by homologous recombination. The transformed yeast strain was selected on the media with starch as the sole carbon source and verified by PCR. The transformant exhibited secretive alpha-amylase activity, low AHAS activity and reduced diacetyl production. Effects of temperature, pH, and metal ions on the activity of the alpha-amylase expressed by the transformant were examined. The fermentation performance of host strain YSF-5 and the transformant was also examined.