Integrating metal organic frameworks (MOFs) and polyelectrolytes (PEs) in membrane reactors for boosting the activity of immobilized carbonic anhydrase

Atmospheric CO₂ levels are now at their highest point and the remediation technology is being actively explored. Carbonic anhydrase (CA) is the enzyme that can help sequester CO₂ from industrial processes. However, enzyme stability under these industrial conditions is a big disadvantage. Herein, we propose a novel dual reactor where we combine an Enzymatic membrane reactor (EMR) with enzyme encapsulation in Metal-organic-framework (MOF) inside one unit − by employing various attachment mechanisms and using polyelectrolytes in different multilayer configurations. The polydopamine (PDA)-assisted co-deposition approach was used for modification of pristine polysulfone membranes. Each immobilization method was evaluated individually first, i.e.: enzyme immobilized on a membrane, enzyme encapsulated in MOF, and the dual reactor. In this work, immobilization of CA on a modified membrane surface showed a 2.5-fold increase of enzyme specific activity (558 vs 220 mU/mg), while encapsulation of CA in MOF significantly improved its thermal stability (11 % vs 92 % of CA activity loss upon incubation at 60 °C). Enzyme immobilized in the dual reactor demonstrated biocatalytic activities up to 744 µU/cm² while retaining up to 59 % of the native membrane permeability. The results shown in this work present the proof of concept of effective integration of MOFs and EMRs to enhance the performance of immobilized CA. Finally, this work shows that selected CA immobilization methods can promote significant increases of activity, particularly at high temperatures, and therefore immobilization cannot only be used for boosting enzyme stability but also activity. This research can pave the way for future exploration of different possibilities for the use of enzymes and methods of their protection without decreasing their performance