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 degrees C). In addition, the enzyme was active and stable at strongly alkaline pH (pH 9.0) and higher temperature (60 degrees 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.