There is a national need to develop carbon-neutral processes for the production of liquid transportation fuels. This project will develop a new process to turn carbon dioxide, a greenhouse gas, and renewable electricity into liquid fuels and chemicals using a unique microorganism integrated into an electrochemical device. Particular efforts will be made to dramatically increase the production of the liquid hydrocarbon heptadecane by genetically engineering the metabolism of the microorganism. Genetic engineering tools will also be developed to make the genetic modifications permanent, which will create robust cell lines capable of making fuels and chemicals in an industrial process using electricity and atmospheric carbon dioxide as the feedstock.
The goal of this project is to develop a new electrofuels platform for producing hydrocarbons from atmospheric carbon dioxide using electricity. The unique electrofuels platform consists of two integrated reactors. The first is a bioreactor containing Acidithiobacillus ferrooxidans cells which are able to grow at low pH using carbon dioxide as their sole carbon source and the oxidation of ferrous to ferric iron as an energy source. The ferric iron is sent to an electrochemical reactor which efficiently reduces the ferric iron back to ferrous iron. The combined reactor system produces biomass from electricity, water and air. The cells have been genetically modified with two different exogenous metabolic pathways for chemical and/or fuel production, and preliminary results show that cells can be transiently transformed to produce small amounts of heptadecane from carbon dioxide. In order to advance this new technology, it will be critical to increase the production of heptadecane and/or other long chain hydrocarbons. This will be accomplished using co-transformations to transiently over-express or knock-down the expression of key metabolic genes to determine strategies to direct the flux of carbon into the production of the fuels. Further development of this technology will require permanent transformation of exogenous genes into the chromosome of these cells. New methods will be developed to edit the A. ferrooxidans genome to enable the chromosomal integration of genes and pathways into this unique host cell system. The best new cell lines will be characterized in the integrated electrofuels platform so that the improvements in efficiency obtained from these maneuvers can be quantified in terms of yield of fuel per kW-hr of electricity utilized. Through these research activities, the project will train a Columbia University graduate student, who will also help to develop content for a distant-learning program to build the capacity of West African experts in the field of sustainable energy systems and solutions. Topics from this course will also be integrated into two graduate level elective courses at Columbia University as well as other outreach activities in the local community.
