Immobilization of bovine carbonic anhydrase on glycidoxypropyl-functionalized nanostructured mesoporous silicas for carbonation reaction

Bovine carbonic anhydrase (BCA) has been immobilized on glycidoxypropyl-functionalized SBA-15 (GFS) for biomimetic carbonation reaction. GFS was characterized by N2 adsorption-desorption, Fourier transform infrared analysis, C-13 and Si-29 CP MAS NMR spectroscopy. The immobilization time and material dose were optimized. The influences of pH value and temperature on the activity of free and immobilized BCA, storage stability and reusability of immobilized BCA were investigated using a para-nitrophenyl acetate (p-NPA) assay. The kinetic parameters K-m and K-cat/K-m for free and immobilized BCA were found to be 2.4 mM and 896.4 M-1 s(-1), and 3.1 mM and 757.4 M-1 s(-1), respectively. It was observed that the immobilized BCA can retain around 91% of its initial activity up to 30 days at 4 degrees C, which showed higher storage stability than free BCA. Reusability studies suggested that immobilized BCA could keep high activity after 20 cycles of carbonation reaction. BCA immobilized on GFS (BCA-GFS) were used for hydration of CO2. The CO2 sequestration capacity in terms of conversion CO2 to calcium carbonate was quantified by organic elemental analysis. The amount of CaCO3 precipitated over GFS-BCA was nearly the same as that precipitated over free BCA, 227 mg of CaCO3/mg of BCA-GFS as compared to CO2 sequestration capacity of 241 mg of CaCO3/mg of BCA. (C) 2015 Published by Elsevier B.V.