Characterisation of the reversible formate dehydrogenases of Shewanella

Davies, Jonathan A. (2017) Characterisation of the reversible formate dehydrogenases of Shewanella. Doctoral thesis, University of East Anglia.

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The reversible action of tungsten or molybdenum-containing formate dehydrogenase (FDH) enzymes in reducing CO2 to formate has been proposed for storing renewably produced electricity with concomitant CO2 sequestration. Previous attempts have highlighted the unfeasibility of using purified enzyme systems for biotechnological purposes. In response the possibility of using the exoelectrogenic bacteria Shewanella oneidensis in association with a cathode to drive intracellular CO2 reduction is proposed. Since the native FDH enzymes of S.oneidensis have not been previously studied, this work concerns their characterisation and directionality to inform both on native physiology and possible future biotechnological applications. This thesis demonstrates that the native FDH enzymes of S.oneidensis are capable of CO2 reductase activity. Both forward (Km 39 μM) and reverse (Km 1.43 mM) directions of FDH catalysis in whole cell cultures are maximal when cultured in the presence of W. When grown under such conditions, two FDH isoforms (Fdh1αβγ and Fdh2αβγ) contribute to these activities, with protein purification confirming Fdh2αβγ as a tungstoenzyme. CO2 reductase activity in S.oneidensis cultures could be driven by a cathode in simple three electrode electrochemical experiments without exogenous mediators with high coloumbic efficiency, representing an interesting paradigm for future inexpensive microbial electrosynthetic study.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: Jackie Webb
Date Deposited: 30 Apr 2018 11:11
Last Modified: 30 Apr 2018 11:11


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