Improving the performance and efficiency of heterotrophic carbon fixation through strain engineering and membrane-based CO2 delivery

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Elevated levels of carbon dioxide in the atmosphere contribute significantly to climate change. Photosynthesis pulls carbon dioxide out of the air and creates sugars. Some microbes are photosynthetic. Other microbes can take up carbon dioxide as they ferment sugars to organic acids. The objective of this project is to improve carbon dioxide uptake and use by non-photosynthetic microbes. Microbes will be engineered to be more efficient. A bioreactor will be developed to enable efficient and direct CO2 delivery to cells. Through research, education, and outreach activities, this project will attract students to STEM disciplines, cultivate their interest in these areas, and inspire them to continue towards advanced degrees and careers in STEM fields. Strategies to address persistent bottlenecks associated with efficient delivery and heterotrophic fixation of CO2 will be evaluated. Succinate production by Escherichia coli will be the model system. High-performance biocatalysts for fermentative CO2 fixation will be engineered. Multiple, synergistic inorganic carbon uptake systems will be added. Protein engineering and evolution strategies to enhance the catalytic activity of phosphoenolpyruvate carboxykinase will be implemented. A series of bioreactors incorporating non-porous hollow-fiber membranes for efficient, bubble-free, and on-demand CO2 delivery will be designed, constructed, and modeled mathematically. Ultimately, these efforts could support CO2 delivery and its heterotrophic fixation at faster rates and at higher efficiencies than the current state of the art.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.