Polyethylenimine-Grafted Silica Nanoparticles Facilitate Enzymatic Carbon Dioxide Conversion

Polyethylenimine (PEI)-grafted silica nanoparticles were fabricated and characterized for the electrostatic immobilization of a CO2 conversion enzyme. PEI was supposed to serve as a carbonic anhydrase mimic for CO2 capture and conversion to HCO3- (the optimal substrate of many CO2 conversion enzymes) and was proved to assist phosphoenolpyruvate carboxylase to form a dual-enzyme cascade system for CO2 conversion. The immobilized enzyme not only presented better thermostability, pH tolerance, and storage stability, but also enhanced the specific activity (three- and fourfold for HCO3- and CO2 as the substrates, respectively), with good reusability and low cost. It was proven that PEI-grafted nanoparticles are highly efficient nanocarriers for immobilizing CO2-converting enzymes in industrial applications.