Optimization of the amino acid composition in glutathione fermentation

In this study, uniform design (UD) method was applied to obtain the optimal amino acid composition in glutathione fermentation by S. cerevisiae T65. Glutamic acid, glycine and cysteine were the three most important amino acids in the synthesis of glutathione. A uniform design experiment with three factors (glutamic acid, glycine and cysteine) at five levels was designed according to the uniform design table U15(53). An optimal amino acid composition of 10 mM glutamic acid, 18 mM glycine, and 3.35 mM cysteine was found. When applying the optimal amino acid composition to the flask culture, the glutathione content in yeast cells reached 1.836%, which was 127% higher than the control.The experiments showed that the optimal strategy of amino acid addition in flask culture comprised two steps: first, 2 mM cysteine was added after 2 h; second, the combined amino acids (10 mM glutamic acid, 18 mM glycine, and 3.35 mM cysteine) were added after 7 h.When the optimal amino acid addition strategy was applied to the batch fermentation, the glutathione yield reached 329.3 mg/L. The glutathione content was 1.67%, which was 72.2% higher than the control.