The Production Of Glutathione Through High Cell Density Culture With Saccharomvces Cerevisiae

Glutathione, synthesized from L-glutamic acid, L-cysteine and glycine in two consecutive steps via y-glutamyl-cysteine synthase and glutathione synthase, is one of the major non-protein thiol compounds. GSH (the reduced form of glutathione) is widely distributed in nature and plays many important physiological roles in living cells.GSH is an intracellular product. Microbial synthesis of GSH by fermentation is one of the most common methods for GSH production at present. In this study, Saccharomyces cerevisiae (Y10), a strain which could accumulate high concentration of GSH intracellularly was selected for GSH production. A series of feasible approaches or strategies were carried out to obtain high yield of cell and GSH. The main contents involved in this thesis are described as follows:(1) A suitable medium has been found by means of single factor experiment and orthogonal design for Y10. The influence of the culture medium for the Y10 synthesis GSH was investigated:the optimal carbon source is glucose and molasses (2:1, the optimal initial concentration is 40 g/L), the optimal organic nitrogen source is Corn pulp powder (50 mmol/L), the optimal inorganic nitrogen source is Diammonium phosphate (20 mmol/L).(2) The influence of the inorganic salt added in the medium for the Y10 synthesis GSH was investigated:Na2HPO4 1.5‰. KH2PO4 1.5‰、MgSO4 3.0‰、CuSO4 0.02‰、FeSO4 0.01‰, ZnSO4 0.01‰.(3) Effects of different cultivation ways on cell growth and GSH production were investigated, results show that exponential glucose feeding is the best choice for high cell density culture, exponential feeding glucose form 10 h, after 36 h fer-mentation, dry cell weight reaches 75 g/L and GSH yield is 900 mg/L.(4) Under the high cell density culture condition, effects of the addition of three amino acids on the GSH production were investigated, at 30 h when the cell growth stopped, the cells density are stable, add the mixture of three amino acids, all of them are 8 mmol/L, after six hours when the fermentation ended, dry cell weight reaches 85.5 g/L and GSH yield is 2080 mg/L.