Enzymatic CO2 capture by immobilized hCA II in an intensified microreactor-Kinetic study of the catalytic hydration

Ex vivo applications of human carbonic anhydrase II (hCA II) for its potential in CO2 capture technologies are emerging due to the formidably large hydration turnover number (k(cat) approximate to 10(6) s(-1)) that Nature endowed this enzyme with to catalyze aqueous hydration of CO2 near diffusion limits. Binding of hCA II enzyme on a solid support is an attractive way to perform CO2 capture and has several advantages, including easier separation of the reaction products without catalyst contamination, ability to recover and reuse the enzyme, increase of the enzyme stability and operational lifetime, continuous operation of enzymatic processes and a flexibility in reactor design. The enzymatic CO2 hydration in the presence of immobilized hCA II in an intensified microreactor was performed in this work. The enzyme immobilization on the inner surface of a nylon tube was carried out by a sequence of several chemical reactions to generate covalent bonds between enzymes and tube surface. The Bradford method and the esterase activity test were performed to estimate the quantities of attached and of active enzymes. The effect of several operational parameters like CO2 and unprotonated buffer concentrations and liquid velocity was studied. A kinetic model of the catalytic CO2 hydration by the immobilized hCA II was developed on the basis of a pseudo random Quad Quad Iso Ping-Pong mechanism. (c) 2013 Elsevier Ltd. All rights reserved.