Utility of thermo-alkali-stable γ-CA from polyextremophilic bacterium Aeribacillus pallidus TSHB1 in biomimetic sequestration of CO and as a virtual peroxidase.

Aeribacillus pallidus TSHB1 polyextremophilic bacterium produces a γ-carbonic anhydrase (ApCA), which is a homotrimeric biocatalyst with a subunit molecular mass of 32 ± 2 kDa. The enzyme is stable in the pH range between 8.0 and 11.0 and thus alkali-stable and moderately thermostable with T values of 40 ± 1, 15 ± 1, and 8 ± 0.5 min at 60, 70, and 80 °C, respectively. Activation energy for irreversible inactivation "E " of carbonic anhydrase is 67.119 kJ mol. The enzyme is stable in the presence of various flue gas contaminants such as SO,SO, and NO and cations Mg, Mn, Ca, and Ba. Fluorescence studies in the presence of N-bromosuccinimide and fluorescence quenching using KI and acrylamide revealed the importance of tryptophan residues in maintaining the structural integrity of the enzyme. ApCA is more efficient than the commercially available bovine carbonic anhydrase (BCA) in CO sequestration. The enzyme was successfully used in biomineralization of CO from flue gas. Replacement of active site Zn with Mn enabled ApCA to function as a peroxidase which exhibited alkali-stability and moderate thermostability like ApCA.