Enzyme-material composites for solar-driven reactions

Thesis

Using sunlight to drive chemical reactions has long been one of the goals in developing sustainable processes. Previous research has focused on solar fuel production in the form of H₂, but this thesis demonstrates that solar-to-chemicals processes can be constructed to produce more complex compounds, using hybrid systems composed of enzymes and inorganic materials.

Tetrachloroethene reductive dehalogenase (PceA), an enzyme that catalyzes the conversion of tetrachloroethene (PCE) to trichloroethene (TCE) and subsequently to cis-dichloroethene (cDCE), was shown to accept electrons from both graphite and TiO₂ electrodes. Irradiation by UV light onto PceA-adsorbed TiO₂ particles led to the selective production of TCE and cDCE, which was not possible without PceA as a catalyst.

Ferredoxin-NADP⁺ reductase (FNR) is a key enzyme in photosynthesis, as it receives energetic electrons from Photosystem I and produces NADPH as an energy carrier for downstream 'Dark' reactions involving CO₂ assimilation. This thesis presents the discovery of FNR activity on indium tin oxide (ITO) electrodes which led to direct electrochemical investigation of the properties of FNR, both in the absence and presence of its substrate, NADP⁺. The FNR-adsorbed electrode, termed 'the electrochemical leaf', rapidly interconverts NADP⁺/NADPH, and this was coupled to a downstream NADPH-dependent enzyme, thus demonstrating a new approach to cofactor regeneration for enzyme-catalyzed organic synthesis. The NADP⁺ reduction by FNR was also driven by light using a photoanode made of visible-light responsive semiconductors.

Authors: Siritanaratkul, B

• DOI: 10.5287/ora-novqmaoon
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: Electrochemistry; Enzyme
• Subjects: Chemistry