Report
Teaser, summary, work performed and final results
Periodic Reporting for period 3 - BioAqua (Water as cosubstrate for biocatalytic redox reactions)
Teaser
Chemistry provides us with a myriad of materials and compounds used in daily life.Chemical synthesis, however, is not always environmentally acceptable. Often, long synthetic routes have to be taken to achieve the goal. As a result, many chemical processes are very...
Summary
Chemistry provides us with a myriad of materials and compounds used in daily life.
Chemical synthesis, however, is not always environmentally acceptable. Often, long synthetic routes have to be taken to achieve the goal. As a result, many chemical processes are very resource-consuming and waste-generating.
Biocatalysis, i.e. the use of natural catalysts for chemical synthesis, has an enormous potential of rendering today\'s chemistry more sustainable. Particularly, oxidoreductases (enzymes catalysing chemical oxidation or reduction reactions) are valuable tools for the organic chemist to perform challenging transformations in a highly selective manner and under mild reaction conditions.
Today, the majority of biocatalytic redox reactions rely on edible cosubstrates (such as glucose) to promote the transformation. On the long-term, this is not sustainable and ethically acceptable.
The aim of this project therefore is to substitute conventional cosubstrates by more acceptable ones. Ideally, water will serve as cosubstrate to drive biocatalytic redox reactions. To activate the unreactive water molecule, photocatalysis will be utilised.
Overall, this project aims at combining photocatalysis with biocatalysis to attain environmentally acceptable and economically feasible reaction schemes.
Work performed
In the first phase of the project, we have evaluated several biocatalysts (enzymes) catalysing chemically challenging reactions. Amongst others, peroxygenases have been chosen as model catalysts.
Peroxygenases (though principally known since he 1960s) are currently experiencing an increased interest as catalysts for the selective oxyfunctionalisation of non-activated C-H-, C-C-, C=C- and C-X bonds. Often, peroxygenase catalyse such oxyfunctionalisation reactions in a highly selective manner and constitute a very valuable tool for chemical synthesis.
As stoichiometric oxidant, peroxygenases utilise hydrogen peroxide (H2O2). This, cosubstrate, however, has to be used with care. Even small concentrations of H2O2 can irreversibly inactivate the production enzyme and thereby challenge the applicability of the reaction schemes.
Therefore, we have evaluated various catalysts capable of generating H2O2 in the reaction mixture (in situ) through catalytic reduction of molecular oxygen (O2) from ambient air. Especially, some inorganic photocatalysts (e.g. titanium dioxide, TiO2) have proven very efficient for this task. These catalysts transform energy from (sun)light into chemical energy that enables us to generate H2O2 in a highly controlled manner.
With this tool at hand, we can now explore the scope of peroxygenase-catalysed oxyfunctionalisation reactions.
Overall, we strive for \'benign by design\' photobiocatalytic oxyfunctionalisation reactions for chemical synthesis
Final results
Today, we have provided the proof-of-concept for sunlight-driven oxifunctionalisation reactions using only water (or some other very simple electron donors such as methanol of formic acid) as electron donor to promote the reductive activation of O2 to H2O2.
Current research efforts focus on: (1) broadening the scope of photocatalysts and oxidoreductases and (2) preparative application of this novel reaction concept.
Especially the latter is in focus now. We are identifying bottlenecks of the first generation photobiocatalytic reactions and evaluating possible solutions. Overall, we aim at preparative applications (e.g. to be dissiminated in a spin-off cohttps://ec.europa.eu/research/participants/grants-app/reporting/VAADIN/themes/sygma/icons/ico6-save.pngmpany).