Abt, M. / Franzreb, M. / Jestädt, M. / Tschöpe, A. (2023)

Chemical Engineering Journal, 2023, 476,146465

Abstract

Enzymes, as green biocatalysts, open new and selective syntheses routes for more efficient and direct process steps with minimal by-products. An innovative approach is the combination of an enzymatic reaction with an electrochemical reaction to provide otherwise expensive co-factors for enzymes electrochemically. However, there is a lack of scalable reactor designs with high volume specific electrode surfaces that are required to achieve competitive space time yields for these electro-enzymatic syntheses. Here, we show for the first time a three-phase fluidized bed electrochemical reactor for co-factor generation that allows in-situ delivery of educts for electro-enzymatic syntheses. The performance of the fluidized bed electrode consisting of highly conductive graphite particles, was characterized for the electrochemical generation of H2O2, the co-factor for e.g. industrially relevant hydroxylation reactions applying peroxygenases, via oxygen reduction. The achieved space time yields range up to 5.15 ± 0.27 g/(L∙d) for batch and 10.47 ± 0.73 g/(L∙d) for continuous operation, while reaching current efficiencies of up to 57.0 ± 8.2 %. As the results were obtained at neutral pH and at low electrolyte concentrations the fluidized bed electrode is especially suitable for integrated systems combining enzymatic and electrochemical reactions in one reaction chamber. By this, we successfully developed a scalable particle electrode reactor for electro-enzymatic synthesis, which takes advantage of the excellent mixing and mass transfer properties of fluidized beds. This reactor allows for controllable co-factor generation through various factors such as pH in the counter electrode, supplied air flow, and applied potential.

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