L-Cysteine production by metabolically engineered Corynebacterium glutamicum

Area of Science:

• Microbiology
• Biotechnology
• Metabolic Engineering

Background:

• L-cysteine is a vital amino acid with significant commercial applications.
• Its biosynthesis in microorganisms like Corynebacterium glutamicum is often limited by feedback inhibition and degradation pathways.

Purpose of the Study:

• To engineer Corynebacterium glutamicum for efficient L-cysteine production.
• To overcome metabolic bottlenecks in L-cysteine biosynthesis and accumulation.

Main Methods:

• Genetic modification of L-Serine O-acetyltransferase (SAT) by mutating the cysE gene to confer resistance to L-cysteine feedback inhibition.
• Overexpression of mutant cysE and a feedback-resistant mutant serA gene to enhance precursor supply.
• Disruption of ldh and aecD genes to minimize by-product formation and L-cysteine degradation.
• Further disruption of NCgl2463 to prevent cystine import and subsequent L-cysteine loss.

Main Results:

• Overexpression of mutant cysE significantly increased L-cysteine production compared to the wild-type strain.
• Simultaneous overexpression of mutant serA and disruption of ldh and aecD further improved L-cysteine yield.
• Disruption of NCgl2463 successfully prolonged the accumulation phase of L-cysteine.
• Achieved a final L-cysteine concentration of approximately 200 mg/L.

Conclusions:

• Metabolic engineering strategies, including enzyme modification and pathway optimization, are effective for enhancing L-cysteine production in C. glutamicum.
• Targeting feedback inhibition, precursor supply, degradation, and import pathways is crucial for maximizing microbial production of L-cysteine.