CO2 Valorization via Rewiring Carbon Metabolic Network

Abstract

Energizing the world sustainably requires revolutionizing the way we harness natural resources. New renewable technologies include the microbiological upgrading of CO2, the primary greenhouse gas that causes climate change. This project aims to develop a new bioeconomy by taking up CO2 and converting it into high-value products using an autotrophic microbe. Specifically, the team constructed an acetogenic bacterium, Clostridium ljungdahlii, and developed gas fermentation processes that convert syngas (CO2/H2/CO) to the platform compound 3-hydroxybutyrate (3HB). The project has achieved several key successes, including the design and construction of 3HB genes in the gas-fermenting bacterium, the identification of a native 3HB pathway, the conversion of syngas to 3HB through strain engineering, and the improvement of the conversion through rational and iterative strain development. The optimized strain has achieved industry-relevant production rates (0.1 g/L/h) and titers (9.2 g/L), and sustained continuous gas fermentation for 3HB production for > 50 days in a bench-top gas bioreactor. The project has both industrial and scientific implications, including the exploitation of host microbes and processes to improve industrial-scale production of value-added compounds from CO2, and the promotion of gas fermentation technology. The team is also strengthening R&D synergies with other teams and industrial partners in the CO2 consortium, developing cutting-edge approaches for rapid and rational engineering of gas-fermenting hosts, and dissecting the thermodynamics and kinetics of processes for biological syngas valorization. So far, one patent application and one research article have resulted from this work, and the team anticipates additional significant outcomes from this project.