One-pot enzymatic conversion of carbon dioxide and utilization for improved microbial growth

We developed a process for one-pot CO<inf>2</inf> conversion and utilization based on simple conversion of CO<inf>2</inf> to bicarbonate at ambient temperature with no energy input, by using the cross-linking-based composites of carboxylated polyaniline nanofibers (cPANFs) and carbonic anhydrase. Carbonic anhydrase was immobilized on cPANFs via the approach of magnetically separable enzyme precipitate coatings (Mag-EPC), which consists of covalent enzyme attachment, enzyme precipitation, and cross-linking with amine-functionalized magnetic nanoparticles. Mag-EPC showed a half-life of 236 days under shaking, even resistance to 70% ethanol sterilization, and recyclability via facile magnetic separation. For one-pot CO<inf>2</inf> conversion and utilization, Mag-EPC was used to accelerate the growth of microalga by supplying bicarbonate from CO<inf>2</inf>, representing 1.8-fold increase of cell concentration when compared to the control sample. After two repeated uses via simple magnetic separation, the cell concentration with Mag-EPC was maintained as high as the first cycle. This one-pot CO<inf>2</inf> conversion and utilization is an alternative as well as complementary process to adsorption-based CO<inf>2</inf> capture and storage as an environmentally friendly approach, demanding no energy input based on the effective action of the stabilized enzyme system.