Expression and characterization of a codon-optimized alkaline-stable carbonic anhydrase from Aliivibrio salmonicida for CO2 sequestration applications.

The CO2 mineralization process, accelerated by carbonic anhydrase (CA) was proposed for the efficient capture and storage of CO2, the accumulation of which in the atmosphere is the main cause of global warming. Here, we characterize a highly stable form of the cloned CA from the Gram-negative marine bacterium Aliivibrio salmonicida, named ASCA that can promote CO2 absorption in an alkaline solvent required for efficient carbon capture. We designed a mature form of ASCA (mASCA) using a codon optimization of ASCA gene and removal of ASCA signal peptide. mASCA was highly expressed (255 mg/L) with a molecular weight of approximately 26 kDa. The mASCA enzyme exhibited stable esterase activity within a temperature range of 10-60 °C and a pH range of 6-11. mASCA activity remained stable for 48 h at pH 10. We also investigated its inhibition profiles using inorganic anions, such as acetazolamide, sulfanilamide, iodide, nitrate, and azide. We also demonstrate that mASCA is capable of catalyzing the conversion of CO2 to CaCO3 (calcite form) in the presence of Ca(2+). It should be noted that mASCA enzyme exhibits high production yield and sufficient stabilities against relatively high temperature and alkaline pH, which are required conditions for the development of more efficient enzymatic CCS systems.