Immobilization of carbonic anhydrase on spherical SBA-15 for hydration and sequestration of CO2

Bovine carbonic anhydrase (BCA) was immobilized on spherical SBA-15 through various approaches, including covalent attachment (BCA-CA), adsorption (BCA-ADS), and cross-linked enzyme aggregation (BCA-CLEA). The spherical SBA-15 was characterized by XRD, BET, and FE-SEM analysis. 29Si CP-MAS NMR was used to confirm the 3-aminopropyltriethoxysilane grafting (an intermediate step in the immobilization technique), and the immobilization of BCA was confirmed by FT-IR spectrum. The catalytic activities for hydration of CO2 were calculated for free and immobilized BCA with and without buffer. The Kcat values for free BCA, BCA-CLEA, BCA-CA and BCA-ADS were 0.79, 0.78, 0.58 and 0.36 s−1, respectively, indicating that BCA-CLEA showed a comparatively higher hydration of CO2 than BCA-CA and BCA-ADS, which was nearly the same as free BCA. The amount of CaCO3 precipitated over free BCA, BCA-CLEA, BCA-CA and BCA-ADS were 140, 138, 135 and 130 mg, respectively. Performance studies, including assays on reusability, thermal stability and storage stability, were also carried out for BCA-CLEA. The results confirmed that BCA-CLEA is reusable, thermally stable and, withstands storage, and is thus a suitable candidate for use in hydration and sequestration of CO2.