Carbon Dioxide Conversion and Utilization Based on Highly-Stabilized Carbonic Anhydrase

Enzymes have attracted attention rapidly due to their promising applications such as biosensors, biofuel cells, proteomics, enzyme-linked immunosorbent assay (ELISA), antifouling and carbon dioxide conversion. In this work, we developed a enzymatic process for one-pot carbon dioxide (CO₂) conversion and utilization based on conversion of CO₂ to bicarbonate at ambient temperature with no energy input, by using carbonic anhydrase and carboxylated polyaniline nanofibers (cPANFs). Carbonic anhydrase was immobilized on cPANFs via the approach of magnetically-separable enzyme precipitate coatings (Mag-EPC), which is made of covalent enzyme attachment, enzyme precipitation and crosslinking with amine-functionalized magnetic nanoparticles. Mag-EPC showed a half-life of 236 days under shaking (200 rpm), even resistance to 70% ethanol sterilization, and recyclability via facile magnetic separation. For enzymatic one-pot CO₂ conversion and utilization, Mag-EPC was used to accelerate the growth of microalga by supplying bicarbonate from CO₂, representing 1.8-fold increase of cell concentration when compared to the control sample. After two repeated uses via magnetic separation, the cell concentration with Mag-EPC was maintained as high as the first cycle of microalgae cultivation. This one-pot CO₂ conversion and utilization can be an alternative as well as complementary process to adsorption-based CO₂ capture and storage as an environmentally-friendly approach, demanding no energy input based on the stabilized enzyme system.