Bioelectrocatalytic Synthesis: Concepts and Applications

Abstract

Bioelectrocatalytic synthesis is the conversion of electrical energy into value‐added products using biocatalysts. These methods merge the specificity and selectivity of biocatalysis and energy‐related electrocatalysis to address challenges in the sustainable synthesis of pharmaceuticals, commodity chemicals, fuels, feedstocks and fertilizers. However, the specialized experimental setups and domain knowledge for bioelectrocatalysis pose a significant barrier to adoption. This review introduces key concepts of bioelectrosynthetic systems. We provide a tutorial on the methods of biocatalyst utilization, the setup of bioelectrosynthetic cells, and the analytical methods for assessing bioelectrocatalysts. Key applications of bioelectrosynthesis in ammonia production and small‐molecule synthesis are outlined for both enzymatic and microbial systems. This review serves as a necessary introduction and resource for the non‐specialist interested in bioelectrosynthetic research.

Advanced Electroanalysis for Electrosynthesis

“…The indirect methods involving the use of redox mediators are often combined with enzymatic methods. For instance, diaphorase has been used for NADH oxidation with methyl viologen (MV 2+ ), ferrocene, cobaltocene, quinone, and osmium-derived redox polymers …”

“…Redox mediators display various structural and electronic properties and thus the choice of the most suitable ones depends upon the enzymatic system used. In general, their redox potential should match the target of the bioelectrocatalytic reaction . For oxidative MET, the reduction potential of the mediator should be more positive than that of the enzymatic cofactor, while for reductive MET it is the opposite.…”

“…They can achieve high turnover rates and current densities and the overpotential is generally lower compared to direct redox or molecular electrocatalysis. 186 Compared to microbial systems, enzymes allow the simplification of the process with limited side reactions and higher selectivity. For instance, the production of ethanol from CO 2 by microbial systems can lead to the concomitant synthesis of butanol and the reverse reaction can also simultaneously occur.…”

“…The most common enzymes employed are diaphorase, lipoamide dehydrogenase (LipDH), ferredoxin NAD(P) + reductase, and AMAPORS (artificial mediator accepting oxidoreductases). 186 Other examples of enzymes less commonly used for NAD(P)H regeneration are formate dehydrogenase (FDH), glucose dehydrogenase (GDH), and glutamate dehydrogenase (GluDH). 197 Most of these enzymes require a redox mediator to transfer electrons.…”

“…For instance, diaphorase has been used for NADH oxidation with methyl viologen (MV 2+ ), ferrocene, cobaltocene, quinone, and osmium-derived redox polymers. 186 For flavin-containing enzymes, cofactor regeneration can be done by molecular oxygen. The principal drawback is the concomitant production of H 2 O 2 that can negatively affect enzyme activity and stability in absence of catalase.…”