Efficient sequestration of carbon dioxide into calcium carbonate using a novel carbonic anhydrase purified from liver of camel (Camelus dromedarius)

Carbonic anhydrase (CA) was successfully used for carbon dioxide (CO2) sequestration. In fact, sequestration of CO2 into value-added products, calcium carbonate (CaCO3), requires a stable and efficient CA that should tolerate high concentrations of CO2 and Ca2+, high pH and high temperature of working process. Herein, for the first time, the present manuscript described the sequestration of CO2 into CaCO3 using a novel CA which was purified and characterized from liver of camel (Camelus dromedarius), an animal that survive extreme desert conditions. The enzyme was a monomer with lower molecular weight (25 kDa), contained Fe as a physiologically-relevant cofactor instead of Zn and showed higher optimum pH (pH 9.0) and temperature (45°C). In addition, the enzyme was active and stable at strongly alkaline pH (pH 9.0) and higher temperature (60°C). IC50 values revealed that camel liver CA was inhibited by metal ions in the following order: Cu2+ > Zn2+ > Fe3+ > Cr3+ > Ni2+ > Cd2+ > Co2+ > Al3+ > Mg2+ > Ca2+, the enzyme needed high concentrations of Ca2+ to reach 50% inhibition. Camel liver CA was effective in accelerating CaCO3 formation in presence of 1, 2, 5, 10 and 20% Ca2+. The formed CaCO3 was characterized by SEM, XRD and FTIR. Interestingly, camel liver CA showed high CO2 sequestration capacity (966.67 mg CaCO3/mg enzyme) in presence of high concentration of Ca2+ (up to 20%). Camel CA represents promising candidate for harsh industrial applications.