Breeding Of Novel Overproduing Glutathione Strain And Studying On Its Fermentation Conditions

A Ethionine- and Zinc Chloride-resistant mutant HY78 was obtained from its parent strain SL21 by UV treatment and rational screening. The glutathione productivity of the mutant reached 76.0mg/L by flask culture, which was 268.9% higher than the parent strain. And the glutathione content in the dried cells reached 10.0mg/L, which was 263.0% higher than the parent strain. A descend of only 13.0% in the glutathione yield of the mutant was observed after ten times of subculture. Therefore, the obtained mutant is a stable strain.Studies were carried out on the fermentation condition through Single Factor design and Orthogonal Test design, which showed that the optimum fermentation condition was culture temperature 30 ℃, initial pH7.0, rotate speed 180r/min, inoculum age 18h, inoculum size 10%, medium volumes 30ml/250ml. And the optimum medium composition was molasses 40g, beef extract 20g, Cys HCl 1.5g, MgSO4 7H2O 9g, KH2PO4 1g , ZnSO4 5mg, water 1000ml. In this condition the glutathione content came to 182.6mg/L, which was 140.3% higher than that of non-optimized medium.In a 3.7L scale batch bioreactor, the rules of glutathione fermentation were studied by batch and fed-batch operation. The result showed that the glutathione content in the batch culture was only 157.mg/L, which was 15.9% lower than shake flask culture. While the glutathione content in the fed-batch culture reached251.7mg/L, which was 59.7% higher than batch culture.