Enzymatic reactive CO2 absorption: biocatalyst development and characterization

Post-combustion CO2 capture strategy asks for novel effective processes avoiding the use of polluting solvents and oriented towards CO2 utilization. Recent research efforts are focused on the development of CO2 absorption processes promoted by the activity of the enzyme carbonic anhydrase (EC - 4.2.1.1) [1, 2]. This ubiquitous enzyme is able to catalyze the CO2 hydration reaction and can be used to enhance CO2 absorption rate into aqueous alkaline solvents such as carbonate solutions. The adoption of the biomimetic strategy for post-combustion CO2 capture is based on the use of environmental friendly solvents. The present contribution reports on recent studies on the development of carbonic anhydrase biocatalysts for CO2 capture through enzymatic reactive absorption by means of different immobilization techniques. The comparison was made between techniques based on enzyme attachment on solid particles and carrier free immobilization techniques. In both cases the use of paramagnetic solids was included in the development of the biocatalysts, so that, magnetic field assisted separation technology can be considered for the design of the absorption unit (confinement/recovery of the biocatalyst in/from the reaction volume). The overview of experimental results highlighted advantages and drawbacks of two different CA-based biocatalysts: CA covalently bound on paramagnetic nanoparticles (CA_MNPs), and Cross Linked Enzyme Aggregates (CLEA) of CA prepared with inclusion of paramagnetic nanoparticles (CA_MCLEA). Moreover, the kinetics of CA_MNPs has been characterized under conditions relevant for the industrial application (K2CO3 solutions at 40°C) and provided tools for further rational design of CO2 capture units.