Bioelectrocatalytic carbon dioxide reduction by an engineered formate dehydrogenase from Thermoanaerobacter kivui

Electrocatalytic carbon dioxide (CO 2 ) reduction by CO 2 reductases is a promising approach for biomanufacturing. Among all known biological or chemical catalysts, hydrogen-dependent carbon dioxide reductase from Thermoanaerobacter kivui ( Tk HDCR) possesses the highest activity toward CO 2 reduction. Herein, we engineer Tk HDCR to generate an electro-responsive carbon dioxide reductase considering the safety and convenience. To achieve this purpose, a recombinant Escherichia coli Tk HDCR overexpression system is established. The formate dehydrogenase is obtained via subunit truncation and rational design, which enables direct electron transfer (DET)-type bioelectrocatalysis with a near-zero overpotential. By applying a constant voltage of −500 mV ( vs . SHE) to a mediated electrolytic cell, 22.8 ± 1.6 mM formate is synthesized in 16 h with an average production rate of 7.1 ± 0.5 μmol h −1 cm −2 , a Faradaic efficiency of 98.9% and a half-cell energy efficiency of 94.4%. This study provides an enzyme candidate for high efficient CO 2 reduction and opens up a way to develop paradigm for CO 2 -based bio-manufacturing. Thermoanaerobacter kivui -drived CO 2 reductase ( Tk HDCR) requires hydrogen as substrate, which can lead to safety issue. Here, the authors engineered Tk HDCR into an electro-responsive carbon dioxide reductase to harvest electrons from either an external mediator or a polarized electroactive surface.