Biophysical and electrochemical studies of the CO-dehydrogenase: towards the design of bio-electrocatalysts for CO/CO2 interconversion

CO2 metabolism plays a fundamental role in biology, as it represents a “building block” for the synthesis of organic molecules in living organisms. On the other hand, the excessive CO2 emissions due to human activity in recent decades requires today the search for effective solutions dedicated to the closure of the carbon cycle. Thus, it is interesting to develop some alternatives inspired by nature. In particular, carbon monoxide dehydrogenase (CODH) catalyzes the reversible reduction of CO2 to CO and represents an attractive biocatalyst in terms of activity, selectivity, ability to operate in mild conditions with low overpotential. In addition, it does not require high production costs and uses earth abundant-metals. For these reasons, several studies have been conducted on [NiFe]-CODHs for applications in electrocatalytic CO2 reduction reaction (CO2RR). Here, we present a novel and efficient method to overproduce the fully active recombinant [NiFe]-CODH from Rhodospirillum rubrum in the easy-to-handle bacteria E. coli. We also developed the stable and favorable immobilization of the enzyme on non-covalently functionalized carbon nanotubes (CNTs), subsequently integrated in a gas-diffusion electrode device. This device has comparable performance to molecular and metal catalysts for CO2RR. Furthermore, the results of this work have paved the way to study and use this powerful biocatalyst in the near future for biotechnological applications.