Enhanced CO2 capture in packed-bed column bioreactors with immobilized carbonic anhydrase

A novel hybrid enzymatic process with human Carbonic Anhydrase II (hCA II) enzyme immobilized on packing surface and magnetic nanoparticles (MNPs) dispersed in liquid absorbent in a gas–liquid packed-bed column bioreactor was proposed. Packing and MNPs surface were amine-functionalized by co-deposition of polydopamine (PDA)/polyethyleneimine (PEI) and hCA II was immobilized on the modified surface via glutaraldehyde. Immobilized hCA II on packing and MNPs displayed a high storage stability even after 40 days, preserving 80% and 84.7% of their initial activities, respectively. CO2 hydration process achieved significant improvements due to the additional hCA II enzyme immobilized on the MNPs surface, functioning as a free solution-phase enzyme, especially when the diffusion limitation of the enzymatic process with immobilized hCA II enzyme on the packing surface was very significant. CO2 absorption performance has been evaluated experimentally and theoretically under different conditions, including buffer type, buffer concentration, and operational parameters. A 3-D model describing the hydrodynamics, mass transport/reaction in liquid/gas phases, accumulation of biocatalytic MNPs in packed bed, reaction and diffusion in enzyme washcoat/liquid film was used to investigate the behavior of the packed-bed column bioreactor. Overall, the results achieved in this work illustrated that packed-bed column bioreactor with immobilized CA enzyme on the packing and MNPs surface is an encouraging green CO2 capture technology design, which improve the utilization of CA enzyme large turnover number.