Immobilization of carbonic anhydrase on polyethylenimine/dopamine codeposited membranes

Carbonic anhydrase (CA) catalyzing CO ₂ hydration has an important application in carbon capture, and its immobilization is very significant. Here, CA was covalently linked by glutaraldehyde (GA) to the surface of poly(vinylidene fluoride) (PVDF) and polyethylene (PE) membranes, which were previously modified via a simple codeposition of polyethyleneimine (PEI) and dopamine (DA). The effects of the modification conditions were investigated, and the membranes were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. The immobilization process was optimized, and the catalytic properties of immobilized CA were studied. The results show that the optimal mass ratio of PEI and DA was 1:1 and the deposition time was 10–12 h, at which the surface amino group density could reach 1.278 × 10 ⁻⁷ and 1.397 × 10 ⁻⁷ mol/cm ² for PVDF and PE, respectively. For enzyme immobilization, the optimal CA and GA concentrations were 0.2 mg/mL and 0.1 wt %, and a maximum activity recovery of about 53% and 76% could be achieved for PVDF-attached CA and PE-attached CA, respectively. Their K _m values were 10.62 mM and 8.6 mM, and the corresponding K _cat /K _m values were 132.2 M ⁻¹ s ⁻¹ and 312.9 M ⁻¹ s ⁻¹ . After immobilization, the storage stability and reusability of CA were much improved.