Engineering Corynebacterium glutamicum for isobutanol production.

Area of Science:

• Metabolic Engineering
• Synthetic Biology
• Microbial Biotechnology

Background:

• 2-keto acid pathways are crucial for producing isobutanol in microorganisms.
• Corynebacterium glutamicum is a well-established amino acid producer with potential for biofuel synthesis.
• Understanding host tolerance to isobutanol is key for efficient microbial production.

Purpose of the Study:

• To engineer Corynebacterium glutamicum as a platform for isobutanol production.
• To investigate the potential of 2-keto acid pathways for higher chain alcohol synthesis.
• To enhance isobutanol titers through genetic modification and pathway optimization.

Main Methods:

• Overexpression of key enzymes (alsS, ilvC, ilvD, kivd, adhA) in C. glutamicum.
• Analysis of isobutanol toxicity and tolerance in C. glutamicum compared to Escherichia coli.
• Genetic modification, including gene inactivation (pycldh background), to redirect carbon flux.
• Longer-term batch cultures to determine maximum achievable titers.

Main Results:

• Achieved 2.6 g/L isobutanol and 0.4 g/L 3-methyl-1-butanol in 48 hours.
• Detected various higher chain alcohols as byproducts, including 1-propanol and 2-phenylethanol.
• Reached 4.0 g/L isobutanol in wild-type C. glutamicum after 96 hours.
• Increased isobutanol production by 25% to 4.9 g/L in a pycldh background strain.

Conclusions:

• Corynebacterium glutamicum can be successfully engineered for isobutanol production via 2-keto acid pathways.
• C. glutamicum exhibits higher tolerance to isobutanol than Escherichia coli, making it a suitable host.
• Further optimization through gene inactivation can enhance isobutanol yields, showing promise for industrial applications.