Abstract: Microbial carbonic anhydrase can accelerate the CO₂ hydration,which is of great significance for the study of global carbon cycle. A bacterium producing extracellular carbonic anhydrase was selected to study the effects of temperature,pH value and Ca²⁺ concentration on bacterial growth and carbonic anhydrase activity in this article. The results showed that the activity of carbonic anhydrase at 25℃ was the highest,which was beneficial to the CaCO₃ precipitation. The precipitation of CaCO₃ was the most in the alkaline environment with the initial pH 8.5. When the Ca²⁺ concentration was 50 mmol/L,the growth and reproduction of the bacterium were the best,too low Ca²⁺ concentration affected the generation of CaCO₃,while too high Ca²⁺ concentration seriously affected the growth of the bacterium and reduced the activity of the bacterium. Finally,the mechanism of CaCO₃ precipitation induced by microbial carbonic anhydrase was studied. Carbonic anhydrase accelerated the hydration of CO₂ into HCO₃^-,and HCO₃^- reacted with OH^-and Ca²⁺ to form CaCO₃ precipitation in alkaline environment and in the presence of calcium source.

Key words: microbial, carbonic anhydrase, enzymatic activity, CaCO₃, mechanism