Effect of amino acids on glutathione production by Saccharomyces cerevisiae

Summary

The constituent amino acids of the glutathione (GSH) tripeptide chain, glutamate, cysteine and glycine, were investigated for positive effects on GSH production in shake-flask cultures of Saccharomyces cerevisiae with glucose as the carbon source. Cysteine was confirmed as the key amino acid for increasing the specific GSH production rate, ϱg, but showed some growth inhibition, especially in the second growth phase (ethanol-assimilation phase). An intracellular cysteine delivery agent, thiazolidine, showed a similar pattern of increased GSH production and growth inhibition, but to a slightly lesser degree, compared with free cysteine. The initial cysteine concentration affected both the specific growth rate, µ, and ϱg, up to about 5 mm for µ and about 2–3 mm for ϱg. Results of the [³⁵S]cysteine-labelling experiments suggest a complicated role of cysteine in increasing GSH production and further investigation may be necessary.