Biomimetic CO₂Sequestration: 1. Immobilization of Carbonic Anhydrase within Polyurethane Foam

Bovine carbonic anhydrase (CA) was immobilized within polyurethane (PU) foam for biomimetic CO 2 sequestration. The catalytic activities for the free and immobilized CA were estimated using para -nitrophenyl acetate ( p -NPA) as the substrate. Because the p -NPA has limited solubility in the aqueous phase, the activities were estimated in Tris buffer containing 10% acetonitrile. A Lineweaver−Burk relationship was employed to estimate the Michaelis−Menten kinetic parameters for the free and immobilized CA. The k cat, K m, and k cat / K m values for the free CA were found to be 2.02 s −1, 12.2 mM, and 166.4 M −1 s −1, respectively. The K m value for the immobilized CA was estimated to be 9.6 mM at the same conditions. The immobilized CA was stable and did not lose any activity over seven consecutive washings and activity tests. While the free CA lost its activity in 45 days stored at 4 °C in refrigerator, the immobilized CA maintained 100% of its activity over a 45 day period stored in Tris buffer at ambient conditions. It was concluded that the immobilized CA as a very stable biocatalyst could be employed in biomimetic CO 2 sequestration.