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Precise l-threonine-to-l-isoleucine pathway regulation for engineering high-efficiency whole-cell biocatalysts
Heng Zhang1,2,3, Fuqiang Song1,2,3, Ke Wang1,2,3
1Science Center for Future Foods, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu, 214122, China.
Synthetic and Systems Biotechnology
|May 25, 2026
Summary
Metabolically engineered Escherichia coli for efficient L-isoleucine (L-Ile) production. This whole-cell biocatalyst achieved high yields and conversion rates, offering a robust framework for industrial amino acid manufacturing.
Area of Science:
- Biotechnology and metabolic engineering
- Microbial biosynthesis of amino acids
- Industrial microbiology
Background:
- L-isoleucine (L-Ile) is vital for food, pharma, and cosmetic industries.
- Current microbial production methods face metabolic bottlenecks and cofactor limitations.
- Efficient, large-scale L-Ile biosynthesis requires advanced engineering strategies.
Purpose of the Study:
- To engineer Escherichia coli for enhanced whole-cell biocatalysis of L-Ile.
- To overcome metabolic bottlenecks and cofactor limitations in L-Ile production.
- To develop transferable strategies for branched-chain amino acid pathway optimization.
Main Methods:
- Metabolic engineering of Escherichia coli BL21(DE3) for L-Ile production.
- Screening of acetohydroxy acid synthase (AHAS) isoenzymes and ilvA feedback inhibition.
- Optimization of genetic circuits including promoter tuning and plasmid copy number.
- Fed-batch fermentation with dual-precursor supplementation.
Main Results:
- Identified AHAS II as the optimal enzyme and relieved ilvA feedback inhibition.
- Achieved a peak molar conversion rate of 98.4% and 40.1 g/L L-Ile in 36 hours.
- Demonstrated a mass conversion rate of 0.36 g/g and production efficiency of 1.11 g/L/h.
- L-threonine supplementation suppressed L-valine byproduct formation.
Conclusions:
- Developed a metabolically engineered Escherichia coli strain for efficient L-Ile biosynthesis.
- Validated whole-cell biocatalysis as a feasible approach for industrial L-Ile production.
- Provided a robust framework and transferable strategies for optimizing branched-chain amino acid production.
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