Two-stage process and strain engineering for continuous bioconversion of CO₂ to butanol

Area of Science:

• Biotechnology
• Chemical Engineering
• Synthetic Biology

Background:

• Efficiently converting gaseous C1 feedstocks like carbon dioxide (CO2) into liquid fuels is a major process engineering challenge.
• Developing sustainable methods for CO2 utilization is crucial for reducing greenhouse gas emissions and creating value-added products.

Purpose of the Study:

• To design and demonstrate an integrated chemostat system for continuous butanol synthesis from CO2 and H2.
• To establish a foundational and scalable framework for CO2 valorization into butanol.

Main Methods:

• A tandem process sequentially coupling two bioreactors with complementary microorganisms.
• Utilizing Sporomusa ovata for autotrophic acetate production from CO2 and H2.
• Employing metabolically engineered Escherichia coli for butanol synthesis using acetate as the sole carbon source.

Main Results:

• Achieved a butanol titer of 422 ± 4 mg L-1 in batch cultures using multi-level metabolic engineering.
• Demonstrated a continuous two-stage system producing 4.8 mg L-1 h-1 of butanol from CO2 via acetate.
• Identified critical optimization targets for future process improvements.

Conclusions:

• The study presents a proof-of-concept for a scalable CO2-to-butanol conversion framework.
• While current titers do not meet economic benchmarks, the integrated system provides a viable pathway for sustainable fuel production.
• Further optimization is needed to enhance efficiency and economic feasibility.