Strain optimization for efficient isobutanol production using Corynebacterium glutamicum under oxygen deprivation

Area of Science:

• Biotechnology
• Metabolic Engineering
• Microbial Fermentation

Background:

• Microbial production of isobutanol is hindered by its high toxicity to cells.
• Corynebacterium glutamicum shows tolerance and high productivity under oxygen deprivation, making it a promising host for toxic chemical production.

Purpose of the Study:

• To develop highly productive Corynebacterium glutamicum strains for isobutanol production.
• To optimize the fermentation process to overcome product inhibition and enhance yield and productivity.

Main Methods:

• Engineered C. glutamicum strains by modulating 2-keto acid decarboxylase (KDC) and isobutanol dehydrogenase (IBDH) activity.
• Suppressed by-product formation and optimized gene expression (kivd, adhP).
• Implemented continuous extraction using oleyl alcohol and increased cell concentration.

Main Results:

• Achieved 343 mM (3.2% v/v) isobutanol production under oxygen deprivation, doubling previous records.
• Enhanced yield by 56.5% through gene disruption (ppc), use of a mutant enzyme (AHAIR), and glycolytic gene overexpression.
• Reached 78.1% yield and 981 mM (9.1% v/v) volumetric productivity with continuous extraction and high cell density.

Conclusions:

• Optimized C. glutamicum strains and fermentation processes can achieve high yields and productivity of isobutanol.
• Overcoming cell toxicity and product inhibition is crucial for industrial-scale production of toxic chemicals.
• Continuous extraction and high cell density fermentation are effective strategies to boost isobutanol production.