Efficient deployment of carbonic anhydrase (CA) in direct air capture (DAC) is constrained by the lack of enzyme durability under alkaline, chemically complex, and long-term operating conditions. A carrier-free self-immobilization strategy based on encapsulin-mediated intracellular assembly was proposed to address these challenges. The fusion of Sulphurihydrogenibium azorense carbonic anhydrase (SazCA) with the encapsulin EncMh from Mycolicibacterium hassiacum enables spontaneous self-assembly into supramolecular particles during expression in host cells, allowing high-yield production and low-energy recovery by simple centrifugation. The resulting SazCA-EncMh assemblies exhibit high thermal stability and broad tolerance toward alkaline and ion-rich environments. Notably, their supramolecular state can be reversibly switched between nano- and microscale assemblies by pH modulation without loss of catalytic activity over multiple cycles. Under DAC, free SazCA-EncMh significantly enhances long-term Chlorella cultivation over 21 days, indicating sustained extracellular catalytic function and improved inorganic carbon availability. In addition, SazCA-EncMh exbibits improved stability relative to ferritin-based assemblies in representative DAC absorbents, including amino acid salts and tertiary amines. Overall, encapsulin-enabled self-immobilization offers a practical and scalable strategy for stabilizing CA under DAC-relevant conditions, supporting its integration into biological and hybrid carbon capture systems.
Deng et al. (Thu,) studied this question.