Mutation Screening And Fermentation Conditions Optimizing Of High Erythorbic Acid Yield Strains

D-erythorbic acid as a new biological antioxidant and preservative is applied widely in food industry. At present, the two-step fermentation of D- erythorbic acid was researched deeply, one-step fermentation was less reported. In order to acquire high yield strains of D-erythorbic acid and use the strains to produce D-erythorbic acid by direct fermentation, the paper did research as follow:1. Mutation breeding of high D-erythorbic acid yiled strainsThrough the treatment of Ultraviolet and diethyl sulfate mutagenesis to parent strain of Penicillium griseofulvum FZ13, there are obtained 27 strains which yield of D-erythorbic acid was increased more than 200%. The yield of Z-83 strain was highest, which yield was 5.82mg/ml and was 4.732 times of the parent strain. Than through protoplast fusion and drug resistance markers screening in high yield strains of Z-83, S-301 and S-402, the result was obtained a higher yield strain which was L-11.L-11 strain was stable genetic traits and the yield of D-erythorbic acid was 6.93mg/ml.2. The mutagenesis fermentation conditions for producing D-erythorbic acid were studiedThe L-11 fermentation conditions for producing D-erythorbic acid were studied By Single Factor Experiment, the result indicated that the match of optimal fermentation carbon resource and nitrogen resource for the strain were:glucose, urea and ammonium sulfate.The optimal culture conditions were:primary pH 5.5,30℃ and 2%-3% inoculate concentration. Based on the single factor test, the fermentation medium was further optimized through Response Surface Methods. According to Central composite design principle, four significant factors of Glucose, urea.ammonium sulfate and zinc sulfate were studied by Four factors of the three level test. The result showed that the match of optimum fermentation culture for producing D-erythorbic acid were:Glucose 80g/L, urea 4.96g/L, ammonium sulfate 4.65g/L and zinc sulfate 0.04g/L. In the optimized fermentation culture, the average yield of D-erythorbic acid was 7.65g/L, which was correspondent with the theory. It improved 10.7% than the yield which was 6.93g/L before optimal.