Immobilized Carbonic Anhydrase for the Biomimetic Carbonation Reaction

Carbonic anhydrase (CA) has been immobilized on surfactant-modified silylated chitosan (SMSC) for the carbonation reaction. CA immobilized on SMSC was characterized using a scanning electron microscope, energy-dispersive X-ray and X-ray diffraction spectroscopy, and Fourier transform infrared analysis. The effect of various parameters, such as pH, temperature, and storage stability, on immobilized CA was investigated using a p-nitrophenyl acetate (p-NPA) assay. The optimum pH and temperature were determined to be 7 and 35 °C, respectively. Kinetic parameters of immobilized and free CA (K m and V max values) were also evaluated. For immobilized CA, the K m value was 4.547 mM and the V max value was 1.018 mmol min−1 mg−1, whereas for the free CA, the K m value was 1.211 mM and the V max value was 1.125 mmol min−1 mg−1. It was observed that immobilized CA had longer storage stability and retained 50% of its initial activity up to 30 days. Proof of concept has been established for the biomimetic carbonation reaction. The CO2 sequestration capacity in terms of conversion of CO2 to carbonate was quantified by gas chromatography (GC). It was 10.73 and 14.92 mg of CaCO3/mg of CA for immobilized and free CA, respectively, under a limiting concentration of CO2 (14.5 mg of CO2/10 mL).