Biomimetic CO₂ capture using a highly thermostable bacterial α-carbonic anhydrase immobilized on a polyurethane foam

Abstract

The biomimetic approach represents an interesting strategy for carbon dioxide (CO₂) capture, offering advantages over other methods, due to its specificity for CO₂ and its eco-compatibility, as it allows concentration of CO₂ from other gases, and its conversion to water soluble ions. This approach uses microorganisms capable of fixing CO₂ through metabolic pathways or via the use of an enzyme, such as carbonic anhydrase (CA, EC 4.2.1.1). Recently, our group cloned and purified a novel bacterial α-CA, named SspCA, from the thermophilic bacteria, Sulfurihydrogenibium yellowstonense YO3AOP1 living in hot springs at temperatures of up to 110 °C. This enzyme showed an exceptional thermal stability, retaining its high catalytic activity for the CO₂ hydration reaction even after being heated at 70 °C for several hours. In the present paper, the SspCA was immobilized within a polyurethane (PU) foam. The immobilized enzyme was found to be catalytically active and showed a long-term stability. A bioreactor containing the “PU-immobilized enzyme” (PU-SspCA) as shredded foam was used for experimental tests aimed to verify the CO₂ capture capability in conditions close to those of a power plant application. In this bioreactor, a gas phase, containing CO₂, was put into contact with a liquid phase under conditions, where CO₂ contained in the gas phase was absorbed and efficiently converted into bicarbonate by the extremo-α-CA.

• Biomimetic
• bioreactor
• carbonic anhydrase
• CO₂ absorption
• polyurethane