The depletion of fossil fuel reserves, global warming, energy security and the need for clean, cheap fuels has made developing sources of renewable energy a global research priority. Microbial Fuel Cells (MFCs) have the potential to generate renewable electricity from a vast array of carbon sources such as waste-water, agricultural by-products and industrial pollutants. In MFCs electrons from microbial metabolism flow from the bacteria toward an anode then on through an external circuit finally converting oxygen into water at the cathode closing the cycle. The optimization of MFC systems is a highly multidisciplinary area of research and two complementary areas of work are required - firstly to design more efficient hardware for the cells by traditional engineering and secondly to understand and improve the interaction and electron transport between microbes and electrode via biological engineering.
One of the most important engineering challenges in MFC development is the efficient electron transfer from the bacteria to the anode. To date three possible methods of transferring electrons from bacterial cells to the electrode have been identified - directly via cell surface cytochromes (e.g. Shewanella spp), via pili acting as nanowires (e.g. Geobacter spp) or via the production of soluble electron mediator compounds (e.g. Pseudomonas sp phenazine production). Fundamental to cell contact with the anode, electron transfer and thus the functioning of the MFC is the formation of specialized biofilms on the electrode surface. It has been shown that the power output of MFCs and that the power density was directly dependent on biofilm growth and composition.
We are using a synthetic biology approach to reengineer bacteria to predictably and efficiently generate and transfer electrons to microbial fuel cell electrodes resulting in a highly versatile, reliable and sustainable energy sources. We aim to -
- Create a synthetic biology toolbox of biological parts and devices for the easy engineering of electrogenic microbial strains and the construction of genetic circuits for enhanced electron transfer capabilities.
- Investigate the structure, composition and activities of electrode biofilms.
- The versatility of carbon metabolism in the bacteria will be engineered to expand the range and efficiency of utilising pollutants as carbon sources for electricity generating metabolism closing the waste - energy loop.
