Abstract
The decarbonization of the chemical industry and a shift toward circular economies because of high global CO(2) emissions make CO(2) an attractive feedstock for manufacturing chemicals. Moreover, H(2) is a low-cost and carbon-free reductant because technologies such as solar-driven electrolysis and supercritical water (scH(2)O) gasification enable sustainable production of molecular hydrogen (H(2)). We review the recent advances in engineering Ralstonia eutropha, the representative species of "Knallgas" bacteria, for utilizing CO(2) and H(2) to autotrophically produce 2,3-butanediol (2,3-BDO). This assessment is focused on state-of-the-art approaches for splitting H(2) to supply energy in the form of ATP and NADH to power cellular reactions and employing the Calvin-Benson-Bassham cycle for CO(2) fixation. Major challenges and opportunities for application and future perspectives are discussed in the context of developing other promising CO(2) and H(2)-utilizing microorganisms, exemplified by Zymomonas mobilis.