Hydrogen-fueled CO2 reduction using oxygen-tolerant oxidoreductases

Hydrogen gas obtained from cheap or sustainable sources has been investigated as an alternative to fossil fuels. By using hydrogenase (H 2 ase) and formate dehydrogenase (FDH), H 2 and CO 2 gases can be converted to formate, which can be conveniently stored and transported. However, developing an enzymatic process that converts H 2 and CO 2 obtained from cheap sources into formate is challenging because even a very small amount of O 2 included in the cheap sources damages most H 2 ases and FDHs. In order to overcome this limitation, we investigated a pair of oxygen-tolerant H 2 ase and FDH. We achieved the cascade reaction between H 2 ase from Ralstonia eutropha H16 (ReSH) and FDH from Rhodobacter capsulatus (RcFDH) to convert H 2 and CO 2 to formate using in situ regeneration of NAD + /NADH in the presence of O 2 .