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The objective of the present study was to develop a single enzyme nanoparticle of carbonic anhydrase (SEN-CA), formed by modifying the surface of CA with a thin layer of organic/inorganic hybrid biopolymer such as chitosan. SEN-CA enhances the rate of CO2 hydration further, for subsequent fixation into stable mineral carbonates, compared to free CA. SENCA shows CO2 sequestration capacity of 147 mg of CaCO3/mg of CA, which is far better than CO2 sequestration capacity of 35 mg of CaCO3/mg for free CA under limiting concentration of CO2 (14.5 mg of CO2/10 ml). SEN-CA showed improved stability compared to free enzyme assayed by carbonation reaction. [ABSTRACT FROM AUTHOR]

Abstract: Carbonic anhydrase (CA) has been immobilized on chitosan beads and has been tested for its activity using p-NPA. CA immobilized chitosan beads were further tested for targeted application of carbonation reaction to convert CO2 to CaCO3. It was observed that onset time for precipitation of CaCO3 was 40s for immobilized catalyst as compared to non-catalyzed system (100s). Mechanistic and kinetic aspects have been addressed for immobilized catalyst as well as free CA using p-NPA assay. K m and V max of the immobilized CA was observed to be 2.36mM and 0.54μmoles/min/ml as compared to K m and V max of 0.87mM and 0.93μmoles/min, respectively, for free CA. Storage stability test was conducted up to 20 days and it was observed that at −20°C, the Half Life Period (HLP) of immobilized CA was 216h as compared to 192h for free CA whereas at 25°C the HLP for immobilized and free CA was observed to be 456h and 408h, respectively. [Copyright &y& Elsevier]