Carbonic Anhydrase Immobilized by ZnO Nanoparticles for Catalytic CO2 Conversion

Carbon capture, utilization, and storage (CCUS) has emerged as a critical strategy in combating climate change and global warming. Carbonic anhydrase (CA) exhibits exceptional potential as a biocatalyst for CCUS processes due to its remarkable ability to accelerate CO 2 hydration. In this study, CA was immobilized on ZnO nanocarriers of varying morphologies. The optimal immobilization conditions and enzymatic properties of the immobilized CA were investigated, followed by catalytic CO 2 uptake and mineralization experiments. The immobilization process resulted in several improvements: enhanced overall thermal stability, an elevated optimal reaction pH of 8.50 (compared to 8.00 for free CA), retention of 84.98% original activity after 30 days of storage at 4 °C, and preservation of 85.36% initial activity after five recycling cycles. While the affinity between immobilized CA and its substrate increased, a decrease in activity was observed. The Michaelis constant (Km) for immobilized and free CA were determined to be 17.22 mM and 34.92 mM, respectively, with corresponding catalytic efficiency (Kcat/Km) of 20.49 M −1 -S −1 and 148.91 M −1 -S −1 . The catalytic performance of immobilized CA was investigated by carrying out the CO 2 adsorption assay. Notably, the catalytic efficiency of immobilized CA in CO 2 absorption and mineralization under various conditions was significantly enhanced. Graphical