Catalytic CO2 hydration by immobilized and free human carbonic anhydrase II in a laminar flow microreactor – Model and simulations

Abstract

Ex vivo applications of human carbonic anhydrase II (HCA II) for its potential in CO2 capture technologies are emerging owing to the formidably large hydration turnover number Nature endowed this enzyme with to catalyze aqueous hydration of CO2 near diffusion limits. In this work, we investigated the CO2 hydration process catalyzed by solution-phase or immobilized HCA II enzyme in a laminar flow microreactor with the purpose to simulate the reaction–transport of HCA II in microchannels. The effects of operating conditions as well as the contribution of carbonic anhydrase on the performances of the CO2 hydration process are presented. Numerical simulations indicate that in laminar flow microreactor with HCA II immobilized on the inner surface of the tube, interpreting the data as a one-dimensional plug flow results will lead to significant error. Therefore, coupling of transport phenomena and surface enzymic reaction necessitates the use of a two-dimensional analysis. Simulations reveal that hydrodynamic and diffusional constraints do not permit reasonable utilization of the immobilized HCA II enzyme in a laminar flow microreactor, even if HCA II has a very high hydration turnover and the uncatalyzed bulk CO2 hydration is the dominant process. In the microreactor with solution-phase HCA II enzyme “plug flow” is achieved under laminar flow conditions and the contribution of uncatalyzed CO2 hydration process is not considerable.