Microbial fuel cells for direct conversion of waste gases into electricity and chemicals
Lab rotation project description
|The overall aim of these training projects is to provide proof of concept that a gas fermenting bacterium (Cupriavidus) can be used in a microbial fuel cell to produce electricity and chemicals directly from dirty waste gases. LR1: Conducting polymer supports for membrane electrode assemblies. State-of-the-art platinum catalysts will be deposited onto polypyrrole supports and combined with Nafion electrolytes in membrane electrode assemblies. The effects of using impure hydrogen gas as the fuel on the cell power output will be evaluated and power-output data will be compared against those of conventional low-temperature fuel cells containing carbon supports fed with pure hydrogen (Supervisor Dr Darren Walsh; School of Chemistry). LR2 Development and fabrication of electrodes to harness electricity from bacterial cell membranes. Cupriavidus membrane Cytochromes or hydrogenase (Hox Z) will be immobilised on an electrode and their ability to modulate iron redox reactions will be used to grow conducting polypyrrole. The functionalised electrode will then be appraised in its ability to mediate electron transfer from the surface of bacteria (Supervisor Dr Frankie Rawson (School of Pharmacy). LR3 Engineering Cupriavidus to link with conductive nanowires. Genetic engineering of hydrogenase (Hox Z) or cytochrome will be used to fuse a snap tag protein to the target. This would then bind conducting polymers functionalised with benzyl guanine to facilitate efficient extracellular electron transfer. The artificial biofilms of Cupriavidus will be fed with waste gas mixtures containing CO2 and hydrogen to simultaneously produce electricity and chemicals. (Supervisor Dr Katalin Kovacs , Dr Frederik Walter and Dr Phil Hill (School of Life Science/Biosciences).
LR1, LR2 and LR3
Linked PhD Project Outline
The PhD will focus on engineering bacteria of the genus Cupriavidus to efficiently transfer electrons to electrodes in a microbial fuel cell. The bacteria can then be cultivated in fuel cell as a biocatalyst for the simultaneous generation of electricity and chemicals.
In the absence of organic substrates, several Cupriavidus strains can grow lithoautotrophically with carbon dioxide and hydrogen as sole carbon and energy source under aerobic conditions. Using gas fermentation, harmful waste gases from industrial processes or pyrolysis can be directly recycled and converted into electricity and chemicals. Importantly, Cupriavidus are capable of utilising dirty gas mixtures of hydrogen and carbon dioxide with hydrogen sulphide and carbon monoxide impurities which cannot be used in conventional chemical hydrogen fuel cells and Fischer-Tropsch catalysts.
Cupriavidus are aerobic organisms that require oxygen to efficiently generate ATP by oxidative phosphorylation and drive anabolic reactions. The use of hydrogen and oxygen gas mixtures in fermentation vessels presents significant safety risks. Using a microbial fuel cell would allow for anaerobic conditions and thus much safer cultivation of Cupriavidus whilst providing a sustainable source of electricity.
In this project we will address a limitation of microbial fuel cells; which is the transfer of electrons from the bacterial respiratory chain to the surface of the electrodes. We will use a synthetic biology approach to initiate biofilm formation on electrodes and establish a direct electron-conducting link between Cupriavidus and the electrode surface. Cupriavidus hydrogenase (HoxZ) or cytochrome, located in the bacterial membrane, will be fused to a snap tag protein. This will covalently bind conducting polymer nanowires functionalised with benzyl guanine to facilitate extracellular electron transfer in the fuel cell. The formation of conducting nanowires will be used to bridge the redox machinery of the bacteria to a conducting substrate within a fuel cell. In the later stages of the PhD the developed microbial fuel cell will be tested on site to act as a sustainable pollutant cleaner in addition to generating energy. Finally strains with synthetic biochemical pathways will be used to convert captured CO2 into useful platform chemicals.