Protein and Metabolic Engineering
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Fuels and Chemicals from CO2 and electricity - Electrofuels
There is a clear need for the development of new strategies for sustainable fuel and chemical production. There is a great deal of interest in biofuels, which are produced using organisms (heterotrophs) that transform organic materials, such as sugars, into fuels such as ethanol. These organic feedstocks are obtained from large-scale agriculture via photosynthesis. However, this approach is intrinsically limited by the low energy capture and transfer efficiency of photosynthesis as well as land and water usage issues. Autotrophic bacteria (which are able to directly utilize CO2 as a carbon source) have recently attracted attention as potentially sustainable biosynthetic platforms for chemical production as autotrophs do not require organic compounds and thus do not involve agriculture.
We are developing an "electrofuels" process which consists of an electrochemical reactor that reduces a mediator molecule which can subsequently deliver electrons to microbes within a bioreactor. In our approach, we have chosen to use iron as the mediator and we have identified a unique bacterium, Acidithiobacillus ferrooxidans, which can grow by oxidizing iron using CO2 as a carbon source. We have developed novel reactor designs and medium formulations to grow the cells efficiently in the electrofuels platform. And, we have developed a genetic system for the bacterium so we can introduce foreign metabolic pathways into the cells to enable them to produce new fuels and chemicals. The net result of this platform is the production of chemicals and fuels from electricity and air, and this could be a pathway forward for eventually producing transportation fuels from CO2 and renewable energy (such as solar).
- Li X, Mercado R, Kernan T, West AC, and Banta S. Addition of citrate to Acidithiobacillus ferrooxidans cultures enables precipitate-free growth at elevated pH and reduces ferric inhibition. Biotechnol Bioeng. 2014 Oct;111(10):1940-8. DOI:10.1002/bit.25268 |
- Khunjar WO, Sahin A, West AC, Chandran K, and Banta S. Biomass production from electricity using ammonia as an electron carrier in a reverse microbial fuel cell. PLoS One. 2012;7(9):e44846. DOI:10.1371/journal.pone.0044846 |