Formate-driven H(2) production by whole cells of Thermoanaerobacter kivui

BACKGROUND: In times of global warming there is an urgent need to replace fossil fuel-based energy vectors by less carbon dioxide (CO(2))-emitting alternatives. One attractive option is the use of molecular hydrogen (H(2)) since its combustion emits water (H(2)O) and not CO(2). Therefore, H(2) is regarded as a non-polluting fuel. The ways to produce H(2) can be diverse, but steam reformation of conventional fossil fuel sources is still the main producer of H(2) gas up to date. Biohydrogen production via microbes could be an alternative, environmentally friendly and renewable way of future H(2) production, especially when the flexible and inexpensive C1 compound formate is used as substrate. RESULTS: In this study, the versatile compound formate was used as substrate to drive H(2) production by whole cells of the thermophilic acetogenic bacterium Thermoanaerobacter kivui which harbors a highly active hydrogen-dependent CO(2) reductase (HDCR) to oxidize formate to H(2) and CO(2) and vice versa. Under optimized reaction conditions, T. kivui cells demonstrated the highest H(2) production rates (qH(2) = 685 mmol g(−1) h(−1)) which were so far reported in the literature for wild-type organisms. Additionally, high yields (Y((H2/formate))) of 0.86 mol mol(−1) and a hydrogen evolution rate (HER) of 999 mmol L(−1) h(−1) were observed. Finally, stirred-tank bioreactor experiments demonstrated the upscaling feasibility of the applied whole cell system and indicated the importance of pH control for the reaction of formate-driven H(2) production. CONCLUSIONS: The thermophilic acetogenic bacterium T. kivui is an efficient biocatalyst for the oxidation of formate to H(2) (and CO(2)). The existing genetic tool box of acetogenic bacteria bears further potential to optimize biohydrogen production in future and to contribute to a future sustainable formate/H(2) bio-economy. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s13068-022-02147-5.