Immobilization of carbonic anhydrase for CO capture and utilization.

Carbonic anhydrase (CA) is an excellent candidate for novel biocatalytic processes based on the capture and utilization of CO. The setup of efficient methods for enzyme immobilization makes CA utilization in continuous bioreactors increasingly attractive and opens up new opportunities for the industrial use of CA. The development of efficient processes for CO capture and utilization (CCU) is one of the most challenging targets of modern chemical reaction engineering. In the general frame of CCU processes, the interest in the utilization of immobilized CA as a biocatalyst for augmentation of CO reactive absorption has grown consistently over the last decade. The present mini-review surveys and discusses key methodologies for CA immobilization aimed at the development of heterogeneous biocatalysts for CCU. Advantages and drawbacks of covalent attachment on fine granular solids, immobilization as cross-linked enzyme aggregates, and "in vivo" immobilization methods are presented. In particular, criteria for optimal selection of CA-biocatalyst and design of CO absorption units are presented and discussed to highlight the most effective solutions. Perspectives on biocatalytic CCU processes that can include the use of CA in an enzymatic reactive CO absorption step are eventually presented with a special focus on two examples of CO fixation pathways: hybrid enzyme-microalgae process and enzyme cascade for the production of carboxylic acids. KEY POINTS: • Covalent immobilization techniques applied to CA are effective for CO ERA. • Biocatalyst type and morphology must be selected considering CO ERA conditions. • Immobilized CA can offer novel routes to CO capture and direct utilization.