Breading Of High Glutathione Producing Saccharomyces Cerevisiae Strain And Optimizing Of Its Fermentation Conditions

In this paper, a high glutathione-production strain was obtained by complex mutagenesis and resistance selection with cadmium sulfate, and optimization of medium and fermentation conditions were studied.In this study, Saccharomyces cerevisiae BV54which was preserved in our laboratory was the parent strain. The UV and DES mutagenesis methods were used to breed high glutathione-production strains, and we got a mutant strain was named as BV54-11-11.The glutathione yield of mutant strain BV54-11-11was98.80mg/L in shake-flask fermentation, GSH content was15.22mg/g.The medium and cultural conditions of the mutant have been optimized by shake flask. The optimal medium for BV54-11-11which was determined by single factor experiment was glucose, corn syrup and (NH4)H2PO4.With SAS software, the path of steepest ascent tests was used to approach the largest response region, and Box Behnken experimental design and response surface method were applied to optimize the conditions of GSH fermentation. The optimized fermentation conditions were as follows:glucose30.15g/L, liquid volume49.72mL/250mL, rotation speed178.76r/min. Under this optimized conditions, the intracellular GSH production and GSH content of mutant BV54-11-11were122.02mg/L and21.44mg/g, which were107.5%and115.7%higher than those of BV54.In order to obtain high glutathione (GSH) yield and dry cell weight, fed-batch fermentation in a5L bioreactor was adopted for glutathione production on the base of the above experiment. The result showed that the feeding could obviously promote the growth of S.cerevisiae and the synthesis of glutathione, and different feeding methods had different influences on the biomass and GSH in the broth. The highest glutathione content and the most weight of dried cells weight reached15.25g/L and340.04mg/L, which were168%and179%higher than shake flask respectively.The effect of amino acids precursor on the production of glutathione by BV54-11-11was studied. It is determined that L-cysteine can significantly enhance the intracellular GSH accumulation in shaking flask culture. After fermenting9h,0.6%of L-cysteine was introduced into medium could greatly improve the biomass and the biosynthesis of GSH.