Carbonic anhydrase immobilization in poly(ionic liquid) based materials for application in CO2 separation by membranes

Abstract

Carbonic anhydrase (CA) has been extensively studied as CO2 hydration kinetics enhancer in CO2 absorption. The main driver is that the hydration reaction is the rate limiting step when applying aqueous benign solvents to capture CO2. To protect the enzyme from the harsh conditions in the stripper, CA is usually immobilized. However, depending on the immobilization method, this procedure can lead to reduction of enzyme activity or increase of mass transfer limitations. Room temperature ionic liquids (ILs) have been proven as potential solvents in biochemical reactions, increasing in many cases the enzyme activity and stability with respect to organic solvents. Furthermore, polymerized ILs (PIL) present high CO2 solubility. Therefore, there has been numerous studies focused on the application of PIL to gas permeation. However, research on enzyme immobilization in PIL based materials is limited. The present study focus on the elaboration, characterization and testing of CA immobilized in poly(ionic liquid) based materials for the development of membranes. Different materials are studied such as hydrophobic and hydrophilic PILs with different cross-linker amounts. They are characterized by delta pH method, pPNA hydrolysis, Bradford assay, FT-IR, SEM, DSC etc. Concerning enzyme activity, changes on Toptimum and pHoptimum are addressed. Additionally, leaching and stability are analysed. Changes in enzyme activity/stability are discussed in terms of interactions with the PIL