Reactive absorption into aqueous solutions promoted by carbonic anhydrase (CA, E.C. 4.2.1.1.) has been often proposed as a post-combustion CO₂ capture process. The state of the art reveals the need for efficient biocatalyst based on carbonic anhydrase that can be used to further develop CO₂ capture and utilization technologies. The present study is focused on the use of a thermostable CA-based biocatalyst. The carbonic anhydrase SspCA, from the thermophilic bacterium Sulfurihydrogenibium yellowstonense, was in vivo immobilized as membrane-anchored protein (INPN-SspCA) on the outer membrane of Escherichia coli cells. The dispersed biocatalyst, made by cell membrane debris, was characterized in terms of its contribution to the enhancement of CO₂ absorption in carbonate/bicarbonate alkaline buffer at operating conditions relevant for industrial CO₂ capture processes. The amount of immobilized enzyme, estimated by SDS-PAGE, resulted in about 1 mg enzyme/g membrane debris. The apparent kinetics of the biocatalyst was characterized through CO₂ absorption tests in a stirred cell lab-scale reactor assuming a pseudo-homogeneous behaviour of the biocatalyst. At 298 K, the assessed values of the second-order kinetic constant ranged between 0.176 and 0.555 L∙mg⁻¹∙s⁻¹. Reusability of the biocatalyst after 24 h showed the absence of free enzyme release in the alkaline solvent. Moreover, the equilibration of dispersed cell membrane debris against the alkaline buffer positively affected the performances of the heterogeneous biocatalyst. These results encourage further studies on the in vivo immobilized SspCA aimed at optimizing the enzyme loading on the cell membrane and the handling of the biocatalyst in the CO₂ absorption reactors.

由碳酸酐酶 (CA, EC 4.2.1.1.) 促进的水溶液反应性吸收经常被提议作为燃烧后的 CO ₂捕获过程。现有技术表明需要基于碳酸酐酶的高效生物催化剂，该催化剂可用于进一步开发 CO ₂捕获和利用技术。本研究的重点是使用基于 CA 的耐热生物催化剂。碳酸酐酶SspCA，从嗜热细菌Sulfurihydrogenibium yellowstonense，被体内固定为膜锚定蛋白（INPN-SspCA）上的外膜大肠杆菌细胞。由细胞膜碎片制成的分散生物催化剂的特征在于其在与工业 CO ₂捕获过程相关的操作条件下对增强碳酸盐/碳酸氢盐碱性缓冲液中的 CO ₂吸收的贡献。通过SDS-PAGE估计的固定化酶的量导致约1mg酶/g膜碎片。生物催化剂的表观动力学通过在搅拌细胞实验室规模反应器中的CO ₂吸收测试表征，假设生物催化剂的假均相行为。在 298 K 时，二级动力学常数的评估值介于 0.176 和 0.555 L∙mg ^-1 ∙s ^{-1 之间}. 24 小时后生物催化剂的可重复使用性表明碱性溶剂中没有游离酶释放。此外，分散的细胞膜碎片与碱性缓冲液的平衡对多相生物催化剂的性能产生积极影响。这些结果鼓励对体内固定化 SspCA 的进一步研究，旨在优化细胞膜上的酶负载和 CO ₂吸收反应器中生物催化剂的处理。