The central aim of our research is to address the thermodynamic challenge of activating carbon dioxide (CO₂), the most oxidised form of carbon, by harnessing the reducing power of hydrogen (H₂) through the coupling of NAD⁺-reducing hydrogenase (SH) from Cupriavidus necator and various formate dehydrogenases (FDH). SHs are enzymes that catalyse the oxidation of hydrogen, releasing electrons in the process. These electrons are typically used to reduce the natural electron acceptor NAD⁺ to NADH. However, SHs can also use artificial electron acceptors such as methyl viologen (MV). On the other hand, FDHs require these electron mediators to convert CO₂ to formate, a precursor that can be further reduced to produce valuable fine chemicals such as dihydroxyacetone (DHA).

However, the reduction of CO₂ to formate using NADH is thermodynamically unfavourable, and the use of MV, despite its efficiency, poses cytotoxic risks. To overcome these challenges, the Lauterbach lab is developing chimeric enzymes that combine functional domains of SH and FDH domains to enable direct electron transfer from H₂ to CO₂. This innovative solution bypasses the need for intermediate electron mediators, thereby increasing the efficiency of the CO₂ reduction process. This innovative approach aims not only to improve the thermodynamic feasibility of CO₂ fixation, but also to mitigate the cytotoxic effects associated with artificial mediators. In collaboration with the Schwaneberg lab, future research will involve the integration of these chimeric enzymes into recombinant C. necator strains, creating a combined CO₂ fixation and energy module to provide a robust biological platform for the sustainable production of valuable chemicals from CO₂.