Studies on Biosynthetic Production of Antioxidant Glutathione Using Microbial Cultures

Glutathione (γ-l-glutamyl-l-cysteinyl-glycine) is a well-known major antioxidant produced in living cells at the concentrations of 1–10 mM. It protects cells from nutritional, environmental, and oxidative stresses. Structurally, it is a nonprotein thiol compound made up of three amino acids – glutamate, cysteine, and glycine with an unusual γ-peptide bond. To meet the increasing commercial demand of GSH as a functional food supplement, various methods for its production methods have been tried. Forms of glutathione (GSH and GSSG) could be produced by enzymatic methods, which are expensive and unprofitable. The microbial biosynthesis could be achieved by fermentation method using natural or engineered microorganisms such as some strains of yeasts Saccharomyces cerevisiae and Candida utilis and some strains of bacteria Escherichia coli and Lactococcus lactis. However, the former approach is not commercially viable because of its high production cost as compared to the latter one, which is more practical and also cost-effective. Certain microorganisms such as Saccharomyces cerevisiae and Candida utilis have been studied as potential microorganisms for GSH production. For enhanced production of glutathione, using a bifunctional enzyme encoded by gshF from Streptococcus thermophilus has been expressed in Escherichia coli.