(201d) Carbonic Anhydrase-Based Nanocomposites for CO2 Conversion and Utilization
For the reduction of carbon dioxide (CO2) in atmosphere, biocatalytic CO2 conversion has been considered as one of promising CO2 reduction technologies. Carbonic anhydrase (CA) is an enzyme that can catalyze the hydration of CO2 to bicarbonate (HCO3-) in a super-fast speed. However, the short lifetime of CA limits its practical application in CO2 reduction. Here, we prepared CA-based nanocomposites for the stabilization of CA activity. Carboxylated polyaniline nanofibers (cPANFs) were synthesized by the copolymerization of aniline and 3-aminobenzoic acid. CA molecules were immobilized on cPANFs via the approach of enzyme precipitate coating (EPC) that consists of enzyme covalent attachment, precipitation and crosslinking. Amine-functionalized magnetic nanoparticles were also introduced to prepare magnetically-separable EPC (Mag-EPC) for the facile magnetic separation. Mag-EPC stabilized the CA activity, and its half-life was 236 days under rigorous shaking (200 rpm). Mag-EPC maintained more than 90% of its initial activity even after the ethanol sterilization for 300 minutes. The bicarbonate (HCO3-) solution from the CA-catalyzed atmospheric CO2 conversion was utilized as a carbon feed for expedited microalgae growth. Mag-EPC enhanced the microalgae growth by 1.8-folds, which was maintained during the recycled uses of Mag-EPC for three times. Highly-stable and magnetically-separable Mag-EPC has successfully demonstrated its potential application for enzymatic CO2 conversion and utilization, and its uses can be expanded to various other enzyme applications that are being hampered by poor enzyme stability.