Enzyme mediated transformation of CO into calcium carbonate using purified microbial carbonic anhydrase.

In this study, a bacterial carbonic anhydrase (CA) was purified from Corynebacterium flavescens for the CO conversion into CaCO. The synthesized CaCO can be utilized in the papermaking industry as filler material, construction material and in steel industry. Herein, the CA was purified by using a Sephadex G-100 column chromatography having 29.00 kDa molecular mass in SDS-PAGE analysis. The purified CA showed an optimal temperature of 35 °C and pH 7.5. In addition, a kinetic study of CA using p-NPA as substrate showed V (166.66 μmoL/mL/min), K (5.12 mM), and K (80.56 sec) using Lineweaver Burk plot. The major inhibitors of CA activity were Na, K, Mn, and Al, whereas Zn and Fe slightly enhanced it. The purified CA showed a good efficacy to convert the CO into CaCO with a total conversion rate of 65.05 mg CaCO/mg of protein. In silico analysis suggested that the purified CA has conserved Zn coordinating residues such as His 111, His 113, and His 130 in the active site center. Further analysis of the CO binding site showed conserved residues such as Val 132, Val 142, Leu 196, Thr 197, and Val 205. However, a substitution has been observed where Trp 208 of its closest structural homolog T. ammonificans CA is replaced with Arg 207 of C. flavescens. The presence of a hydrophilic mutation in the CO binding hydrophobic region is a further subject of investigation.