A synthetic biology approach to optimisation of microbial fuel cell electricity production

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. MFCs have the advantage that they can vary from micro fluidic to waste water treatment plant scale depending on the desired application.
A great deal of work has been published on optimizing microbial fuel cell electricity generation by exploring the range of carbon sources for metabolism, modifying the design and electrode composition of the fuel cell and examining the microbial community composition and structure occurring in MFCs. However there are still many obstacles that need to be overcome before this technology can be effectively put to use. 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.
The objective of this proposal is to use 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. Synthetic biology aims to use a rigorous engineering approach to design and build new standardized biological parts, devices and systems or to reconfigure existing ones to be more efficient or to carry out new functions and has the potential to revolutionise how we conceptualise and approach the engineering of biological systems. This project aims to -
a) 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 the enhanced production of nanowire pili, surface active cytochromes and production of electron mediator compounds. b) Engineer cells to have enhanced electron transfer capabilities. c) Investigate the structure and composition electrode biofilms formed by the engineered bacteria individually, in combination with each other and their prevalence and persistence when introduced to a naturally occurring anodic biofilm derived from a variety of waste-waters. d) 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 disposal energy generation loop which would be of obvious and enormous benefit to a wide range of industries.

The depletion of fossil fuel reserves, global warming, fears over energy security and the need for clean, cheap fuels has made developing sources of renewable energy a global research priority with the potential to transform industry and society. The project will use cutting edge synthetic biology techniques to optimize the power production by Microbial Fuel Cells (MFC) resulting in highly versatile, reliable and sustainable energy sources. The project aims to deliver synthetic engineered organisms with the ability to produce enhanced power densities. We will synthesise and characterize a novel synthetic biology toolbox of genes, regulatory elements and delivery vectors which will be made freely available to the synthetic biology community via the open access BioBrick Registry at MIT. They will be valuable for future researchers interested in biological electron transfer, microbial communities and cell-cell communication, metabolic engineering, nanofactories for high value chemicals and whole cell biosensor applications.
Sources of cheap, renewable, carbon neutral energy are key to the future of the global economy and this proposal seeks to enhance MFC power production so that they become an economically viable, reliable power source. This project will provide new scientific advances and state of the art techniques in the enhanced fundamental understanding and predictability of natural processes including electron transfer, biofilm formation, anode microbial community structure, diversity and dynamics which can be used to optimize conditions and communities for maximum power production by MFC.
There are a number of industries where this work would be of great interest. Approximately 3-5% of UK electricity consumption is on waste-water treatment. MFC have the potential to use waste-water as a fuel source for power production yielding significant energy savings. MFC based biosensors also could be used for real-time monitoring of inflow to treatment plants providing an early warning system for toxicants that cause the biologically based treatment process to crash with major economic impacts.
There is potential for MFC to use pollutants as a fuel source for power generation. MFC electrodes can be used for enhanced bioremediation in anaerobic environments, field based biosensors for monitoring remediation processes, end of pipe remediation bioreactors and monitoring and on site power generation with enormous environmental and societal benefits. This technology lends itself to power generation in remote areas. This is particularly useful in the developing world where there is very limited infrastructure. The provision of lighting and power would have a dramatic impact on education and quality of life in isolated communities.
An understanding of biofilm formation is important for industry since biofilms can result in the corrosion of pipes and cause major issues for food processing, healthcare products and medical devices. The proposal impacts on health care since infection causing biofilms can form on a range of medical implants and devices and an enhanced understanding of their formation and behaviour is of great medical interest. A greater understanding of anaerobic biofilm behaviour is of particular interest as Ps aeruginosa infection and formation of antibiotic resistant biofilms is the major cause of death for patients with the lung disease cystic fibrosis.
The UK has the potential to be a world leader in synthetic biology based research but in order to reach its full potential there needs to be capacity building of skills development and training of young scientists. An exciting aspect of synthetic biology is that it encourages collaboration and multidisciplinary approaches to research and it is important that the UK develops people who want to engage with diverse ideas and technologies. We will engage in a number of diverse outreach programmes and deliver talks to varied audiences including schools and the public.