Engineering cyanobacterial carbonic anhydrase surface mutations for fast CO₂ hydration and capture

Equilibration between CO₂ and the other forms of dissolved inorganic carbon (DIC) is slow under ambient conditions, bottlenecked by the hydration of dissolved CO₂ to form bicarbonate and a proton. This step is often rate-limiting for aqueous CO₂ capture processes under ambient temperature and pressure, and is precisely the chemistry catalyzed by the family of carbonic anhydrase enzymes. As a result, incorporation of carbonic anhydrases (CAs) into various CO₂ capture schemes may be used to accelerate CO₂ hydration, increasing the rates of downstream processes coupled to this DIC equilibrium. While this potential use for CA has been long-studied, extending these basic chemical principles to real applications have been hampered by practical questions of how to economically source carbonic anhydrase enzymes at mass scale. This work explores the use of modified cyanobacterial expression hosts as a potential resolution to that problem. Successful engineering of carbonic anhydrase surface display in fast-growing, marine cyanobacteria would yield a self-sustaining CO₂ hydration catalyst that requires only sunlight, CO₂ itself, and nutrients freely available in seawater, as inputs for passively generating carbonic anhydrases on the cell envelope during cell growth.