Engineering Escherichia coli for efficient glutathione production.

Area of Science:

• Biotechnology
• Metabolic Engineering
• Microbial Fermentation

Background:

• Glutathione is a vital tripeptide used across pharmaceutical, food, and cosmetic industries.
• Current yeast fermentation methods for glutathione production suffer from intracellular accumulation, limiting yields.
• Escherichia coli offers a promising alternative host for efficient glutathione biosynthesis and secretion.

Purpose of the Study:

• To engineer Escherichia coli for high-yield, extracellular glutathione production.
• To optimize fermentation conditions and genetic modifications for maximizing glutathione titers.
• To establish a cysteine-free fermentation process for industrial glutathione production.

Main Methods:

• Genetic engineering of E. coli by overexpressing glutathione synthesis genes (gshA, gshB).
• Employing strategies to enhance production, including inhibiting degradation, attenuating uptake, and boosting cysteine synthesis.
• Utilizing fed-batch fermentation with optimized nutrient feeding (ammonium sulfate, glycine) and supplementation (sodium thiosulfate).

Main Results:

• Engineered E. coli strain KG06 achieved an initial titer of 19.6 g/L glutathione.
• Metabolic analyses identified the O-acetylserine to cysteine conversion as a rate-limiting step.
• Supplementation with sodium thiosulfate increased the final glutathione titer to a record 22.0 g/L.
• Demonstrated successful glutathione fermentation without exogenous cysteine addition.

Conclusions:

• Developed a highly efficient E. coli fermentation platform for glutathione production.
• Achieved the highest reported glutathione titer to date, demonstrating significant industrial applicability.
• This study presents the first report of glutathione fermentation in E. coli without cysteine supplementation.