Activity and Stability Enhancement of Carbonic Anhydrase Entrapped Within Biomimetic Silica by Methyl-Substituted Silanes

Carbonic anhydrase (CA), an enzyme that accelerates CO2 hydration, is one of the most widely used enzymes in the aid of CO2 sequestration. We entrapped CA from Sulfurihydrogenibium azorense (SazCA) within biomimetic silica; to enhance the activity of the entrapped enzyme, the microenvironment of the silica particles was modified by using methyltrimethoxysilane (MTMS) or dimethyldimethoxysilane (DMDMS) as part of the precursors. When 10% (mol/mol) MTMS or 20% DMDMS was added to tetramethoxysilane (TMOS), the activity of entrapped SazCA increased by almost threefold when compared with the control group without these methyl-substituted silanes. In addition, all three types of entrapped SazCA, namely, the silica formed with only TMOS, 10% MTMS in TMOS, and 20% DMDMS in TMOS, exhibited improved thermal stability and pH stability. All three types of entrapped SazCA also showed good storage stability, with at least 79% of their initial activities retained after being stored at room temperature for six weeks, while the activity of the free enzyme dropped to 14% after only two days. When all three types of entrapped SazCA were applied to carbon sequestration, the efficiency remained above 90% even after ten cycles of reuse.