Carbonic Anhydrase Immobilization on Stabilized Lignin Nanoparticles for Aqueous-Phase Carbon Dioxide Capture

Abstract

The continuous rise in atmospheric carbon dioxide (CO2) concentration and its contribution to global climate change necessitate the development of sustainable CO2 capture technologies. Enzyme-based CO2 capture systems, particularly those using carbonic anhydrase (CA), offer high catalytic efficiency, but their practical use is limited by high enzyme costs, reduced enzyme stability, and the difficulty of recovering them from water-based systems. Here, we report the immobilization of CA via straightforward adsorption onto sustainable and covalently stabilized lignin nanoparticles (sLNPs) for catalyzing aqueous-phase CO2 capture. The immobilized enzyme exhibited slightly higher specific activity than the free enzyme at technically important pH 9.0, which suggests that pH-stable sLNPs may contribute to stabilizing carbonic anhydrase within its microenvironment. The catalytic performance of the system was evaluated in a stopped-flow reactor by measuring CO2 hydration at pH 7.1 and 9.4 across temperatures between 30–60 °C, using the colorimetric response of pH-sensitive dyes. The reaction kinetics at pH 7.1 showed an Arrhenius-type temperature dependence, while non-Arrhenius behavior was observed at pH 9.4. Enzyme immobilization enhanced aqueous absorption of CO2, as shown by stirred-cell fall-in-pressure measurements at 40 and 60 °C. These results support the development of scalable biocatalytic systems for CO2 capture in aqueous media using CA.