Integrated sustainable energy production from food wastes using dual harnessed hydrogenases and novel fuel cell

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Hydrogen biomanufacture via fermentation of sugary wastes will be increased by use of an upregulated synthetic hydrogenase-3 mutant of E. coli, further improved by the superimposition of mutations in the twin arginine uptake system (tat) in order to reduce competing hydrogen consumption and also increase the flux into formate as hydrogen precursor. Bio-H2 will be directed into a proton exchange membrane fuel cell to make electricity, and the savings in potential atmospheric burdens c.f. conventional anerobic digestion or combustion will be calculated. PEM fuel cells, although the most efficient, are unattractive because of the cost of the precious metal electrodes. Recovery of Pd/Pt from wastes will be achieved by harnessing the hydrogenase 1 and 2 functions of E. coli, using overproduced enzymes, engineered to channel the electron flow (for reduction of PD(II)/Pt(IV) into the periplasm. The quality of the Bio-Pd(0) depends on the nucleation site (evidence has suggested that this is the hydrogenase enzyme itself), and also the local environment: the hydrogenase enzymes themselves will be targeted towards various cell surface compartment localisations and the effect of these changes on the quality of the recovered metal nanoclusters assessed. Such assessment will entail measurement of ferromagnetism (in order to calculate the nanocluster size, typically about 5 nm) as well as simple catalytic testing (laboratory reactions) as a measure of the efficacy of the biomaterial. The best bio-nano-Pd(0)/Pt(0)s will be used to fabricate fuel cell electrodes (via established processing and fabrication techniques) which will be used in place of commercially supported precious metal catalysts. The bio fuel cells will be substituted in place of the commercial fuel cells in an integrated test rig run on bio-H2. The rig will be run continuously using food processing waste as feedstock and the electricity yield per cubic metre calculated. The savings in greenhouse gas emissions will be calculated using wild-type and recombinant E. coli, and we will also address the hidden economic/environmental savings from reduction in landfill, and use of environmentally-friendly recovery of precious metals into valuable materials from the spent autocatalyst mountain, as domination by the internal combustion engine makes way for H-fuelled transport. These calculations will be made by the industrial partners in the consortium using our data. Joint with BB/C516128/1