Breeding Of Anti-aging Brewing Yeast Strains

The relationship between Glutathione (GSH) and antioxidant properties of beer was studied. In order to improve the anti-aging capabilities of beer, Saccharomyces cerevisiae S5was mutagenized by ultraviolet radiation and DES to select the rriutants with higher GSH production abilities, and the fermentation properties, antioxidant abilities of mutant were studied briefly. The multi-copy expression of MET4in both laboratory strain YS58and S. cerevisiae S5were also studied which encodes the main transcription activator of the sulfate-assimilating pathway.Different amounts of GSH were added to beer, then we measured the anti-oxidant properties of beer. The results showed that with the incresement of GSH content in beer, DPPH radical scavenging rate increased, TBA value decreased, RSV value increased. It is indicate that GSH is an effective anti-oxidants, and a small content of GSH could enhance the flavor stability of beer.Using strain S5as the parent strain, the mutant SC67was obtained after UV irradiation and DES mutagenesis. The GSH concentration and intracellular GSH content reached15.238mg/L and11.292mg/g respectively, which increased by91.4%and57.8%compared with original strain S5. The extracellular GSH concentration in the beer fermented with SC67was6.43mg/L, which was increased significantly compared with S5which extracellular GSH concentration was1.35mg/L.The anti-aging property of beer was also improved, the DPPH radical scavenging capacity increased by13.2%, the TBA value decreased by7.1%and the RSV value increased by49.2%.The gene MET4which contains500bp promoter was cloned by PCR. The resulted gene MET4was ligated into a plasmid YEp352and a expression vectors Y-M was constructed, and transformed into laboratory strain YS58by electroporation method; YEp352and copper resistance gene CUP1were ligated, followed by the connection of gene MET4, to construct the recombinant plasmid Y-C-M, then Y-C-M was transformed into strain S5. However, compared with the original strain, the intracellular glutathione content and the amount of sulfur dioxide produced by the two kinds of transformant were almost unchanged.