Development of a high performance electrochemical cofactor regeneration module and its application to the continuous reduction of FAD

Technical reactor limitations and low productivities have been shown to limit the implementation of electroenzymatic syntheses beyond lab-scale. One possible solution is a continuous flow-through reactor based on electrochemical plate and 6 frame filter press cells, as proposed in this study. With the aim of maximizing electroenzymatic productivities, the developed reactor set-up allows high electrochemical cofactor regeneration rates using porous, three-dimensional reticulated vitreous carbon electrodes with exceptionally large surface areas up to 19,685 m2 m−3. This system provides increased mass transfer rates and flavin adeninedinucleotide (FAD) was reduced at rates up to 93 mM h−1. The electrochemical FAD reduction was coupled to the styrene monooxygenase (StyA) catalyzed (S)-epoxidation of styrene. Electroenzymatic productivities increased with FAD reduction rates up to 1.3 mM h−1. This set-up now set the stage for efficient in vitro FAD regeneration and allows a broad electrochemical application of flavin dependent enzymes as biocatalysts.