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 CO2 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 CO2 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 degrees 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 CO2 adsorption assay. Notably, the catalytic efficiency of immobilized CA in CO2 absorption and mineralization under various conditions was significantly enhanced.