Abstract
Efficient and durable biocatalysts are important for sustainable CO(2) capture technologies, but enzyme stability often limits their use under harsh process conditions. Here, we evaluate carbonic anhydrases (CAs) adsorbed onto aminated mesoporous SBA-15 as biocatalysts for CO(2) capture under the hypothesis of adsorption-induced thermal stabilization. Carbonic anhydrase from the thermophilic bacterium Persephonella marina (pmCA) and commercial bovine erythrocyte carbonic anhydrase (bCA) were used. Enzyme adsorption isotherms for pmCA and bCA onto the aminated SBA-15 were established, along with desorption tests. Adsorbed and free pmCA and bCA were incubated at 40-90 °C for 14 d. The structural integrity and possibility of amine leaching of the incubated (90°, 14 d) aminated SBA-15 were analyzed by X-ray diffraction (XRD) and NMR spectroscopy. The reaction product speciation in CO(2)-loaded catalyzed and uncatalyzed dispersions was monitored using infrared (IR) spectroscopy. The maximum enzyme adsorption capacities were established to be 1.4 ± 0.2 g pmCA·g-aminated SBA-15(-1) and 2.1 ± 0.5 g bCA·g-aminated SBA-15(-1), with no detectable desorption. Adsorbed pmCA and bCA maintained high activity for 14 d at 40-65 °C and for 4 d at 90 °C, whereas free enzymes lost activity within 4 d at all temperatures. The XRD patterns of the heat-treated (90 °C, 14 d) aminated SBA-15 indicated a full collapse of the mesostructure. IR spectroscopy confirmed enhanced HCO(3)(-) formation in the presence of immobilized CA. Overall, enzyme adsorption onto the aminated SBA-15 significantly improved the thermal stability and activity of pmCA and bCA compared to the free enzymes, demonstrating the potential of adsorbed CAs for biocatalysis.