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Understanding the chemical environment of bioelectrocatalysis

Understanding the chemical environment of bioelectrocatalysis

Significance

Enzyme bioelectrochemistry is the integration of oxidoreductase genes into electrodes. This allows and studies the transfer of electrons between solid-state materials and biological catalysts. To immobilize enzymes at higher levels and create greater current densities, high surface-area strategies have been used. However, these porous electrode structures increase the formation local chemical gradients. Changes in the local environment (substrat concentration, pH and electrolyte species concentration) are key factors in enzyme activity and selectivity. This is where electrochemistry and computational techniques can be used to optimize the local environment for the fuel-producing oxygenoreductases, hydrogenase, and formate dehydrogenase within porous electrodes.

Abstract

Bioelectrochemistry utilizes a variety high-surface-area macroporous and mesoporous electrode architectures to increase the protein loading and the electrochemical response. Although the local chemical environment was studied in heterogenous and small-molecule electrocatalysis, enzyme electrochemistry conditions are still largely established using bulk solution assays. This is despite the fact that it does not take into account the nonequilibrium conditions within the confined electrode space. We use electrochemical and computational methods to study the local environment for fuel-producing oxygenoreductases within porous electrode structures. This improved understanding of local conditions allowed for simple manipulation of electrolyte solutions by adjusting bulk pH and buffer KYou can find more information atTo achieve the optimal pH local to maximize enzyme activity When the electrolyte is applied to macroporous inverted opal electrodes the benefits of higher loading were utilized. The electrolyte was then adjusted to reach 8.0mA cm2H2Evolution reaction and 3.6mA cm2CO2Reduced reaction (CO).2RR) demonstrating an 18-fold improvement over previously reported enzymatic COP2RR systems. This research highlights how important it is to understand the confined enzymatic environment. It will expand the capabilities of enzyme-bioelectrocatalysis. These considerations and insights can be directly applied to both bio(photo)electrochemical fuel and chemical synthesis, as well as enzymatic fuel cells, to significantly improve the fundamental understanding of the enzymeelectrode interface as well as device performance.

Footnotes

    • Accepted November 16, 2021
  • Contributions by authors: E.E.M. E.E.M. E.R. designed research; E.E.M. performed experimental research; S.J.C. E.E.M., S.J.C. and E.R. performed computational modelling. A.M.C.O. and I.A.C.P. provided the enzymes and conducted solution studies. E.E.M. analyzed data. E.E.M. The paper was co-authored by E.R.

  • The authors declare no competing interests.

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  • This article is a PNAS Direct Submission. N.P. N.P.

  • This article contains supporting information online at https://www.pnas.org/lookup/suppl/doi:10.1073/pnas.2114097119/-/DCSupplemental.

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