Accelerated carbonate weathering by immobilized recombinant carbonic anhydrase

Abstract

CO₂ absorption in aqueous alkaline solutions promoted by carbonic anhydrase (CA) has received increased attention as a solution for post-combustion CO₂ capture. In particular, accelerated weathering has emerged as an alternative approach for CO₂ capture, mimicking nature’s way to sequestrate CO₂. In this study, an evolved CA from Desulfovibrio vulgaris was immobilized on magnetic nanoparticles (MNPs) offering a promising solution for the effective enzyme separation and recovery from complex and heterogeneous reaction media. The immobilization yields were high (86–98 %) and MNPs-DvCA8.0 were characterized based on standardized CO₂ release and CO₂ absorption assays and compared to the free enzyme. As a following step, MNPs-DvCA8.0 were applied as promoter in the accelerated weathering of insoluble lime mud, originating as a residue from a paper and pulp industry. MNPs-DvCA8.0 could be efficiently separated, washed and reused for up to 10 consecutive reaction cycles, offering a biocatalyst productivity equal to 2.83 g captured CO₂/g CA opposite to the free enzyme that offered only 1.01 g captured CO₂/g CA. CA immobilization could offer a mitigation strategy for the non-selective adsorption of the free enzyme on lime mud particles during the CO₂ capturing reaction. The highly reproducible and robust immobilization method, that provides material separation based on its magnetic properties, could be a viable solution for the recovery of enzyme and its separation from the lime mud slurry, aiding in obtaining a highly pure solution rich in bicarbonate, as product.