Optimization strategies for CO biological fixation.

Global sustainable development faces a significant challenge in effectively utilizing CO. Meanwhile, CO biological fixation offers a promising solution. CO has the highest oxidation state (+4 valence state), whereas typical multi‑carbon chemicals have lower valence states. The Gibbs free energy (ΔG) changes of CO reductive reactions are generally positive and this renders it necessary to input different forms of energy. Although biological carbon fixation processes are friendly to operate, the thermodynamic obstacles must be overcome. To make this reaction occur favorably and efficiently, diverse strategies to enhance CO biological fixation efficiency have been proposed by numerous researchers. This article reviews recent advances in optimizing CO biological fixation and intends to provide new insights into achieving efficient biological utilization of CO. It first outlines the thermodynamic characteristics of diverse carbon fixation reactions and proposes optimization directions for CO biological fixation. A comprehensive overview of the catalytic mechanisms, optimization strategies, and challenges encountered by common carbon-fixing enzymes is then provided. Subsequently, potential routes for improving the efficiency of biological carbon fixation are discussed, including the ATP supply, reducing power supply, energy supply, reactor design, and carbon enrichment system modules. In addition, effective artificial carbon fixation pathways were summarized and analyzed. Finally, prospects are made for the research direction of continuously improving the efficiency of biological carbon fixation.