Electrofuel Production Using Ammonia or Iron as Redox Mediators in Reverse Microbial Fuel Cells

The production of electrofuels requires the efficient transport of electrons from an electrochemical system into a biological system.  We have approached this challenge by identifying natural chemical mediators that

1. can be easily reduced electrochemically and
2. are natural substrates for different bacterial strains, thus eliminating the need to engineer this aspect of primary metabolism in the biological hosts. 

In our first project we have constructed a reverse microbial fuel cell using the ammonia oxidizing bacteria, N. europaea. These cells grow planktonically and they efficiently oxidize ammonia to nitrite while fixing carbon dioxide.  We have developed an electrochemical reactor to reduce the nitrite back to ammonia so that we are producing biomass from electricity and air.  We have recently engineered the N. europaea cells to produce isobutanol, which is a transportation infrastructure compatible biofuel. 

In a second project we are working with A. ferrooxidans, which is an iron oxidizing bacteria used in biomining operations.  The oxidized iron can be readily reduced electrochemically, and efforts are underway to engineer these cells to make isobutanol as well.  As these processes are developed and optimized, they may be able to produce biofuels and other petroleum derived chemicals from electricity and air.