Activity enhancement of carbonic anhydrase in Chlamydomonas sp. for effective CO sub(2) sequestration

Present study describes the induction of carbonic anhydrase (CA) activity in Chlamydomonas sp. in presence of calcium carbonate. Results indicated that calcium carbonate increased the activity of extracellular CA enzyme by 14-fold compared to culture grown at 3 % CO sub(2), and by fourfold compared to the culture grown at 0.03 % CO sub(2). CA was purified by gel exclusion followed by ion exchange chromatography. Molecular weight of the purified CA was found to be approximately 28 kDa. The enzyme showed optimum stability in the pH range of 8.0-9.0 and temperature of 35 degree C. CA activity was inhibited with Hg super(2+) and Pb super(2+), while Zn super(2+) was found to accelerate its activity. Purified CA was employed for carbonation reaction with CO sub(2) and the calcite produced was characterized by scanning electron microscope and X-ray diffraction. The enhancement in CA activity was found to be reliable, convenient, and may be employed for CO sub(2) sequestration using whole cells or immobilized bioreactor systems.