Experimental study on calcium carbonate precipitates induced by bacillus megaterium

Compared with Sporosarcina pasteurii, the Bacillus Megaterium shows higher enzyme activity in low temperature. Experiments were conducted with Bacillus Megaterium in 30 °C of temperature. In the process of culturing bacteria, urea was added to the medium, and urea concentration varied from 0 to 20 g/L. The concentration of urea and calcium acetate remained 0.5 M in gelling solution in mineralization reaction. The effect of urea concentration on Bacillus Megaterium inducing calcium precipitation was studied. Then the ion concentration in gelling solution varied from 0.25 to 1.25 M with the urea concentration of 10 g/L, and the effect of ion concentration in gelling solution on Bacillus Megaterium inducing calcium precipitation was researched as well. Results show that adding urea to the medium can significantly accelerate the reaction and increase the amount and productive rate of precipitation. The amount of calcium precipitation grows with the higher urea concentration, while there is relatively small difference of productive rate between 10 g/L of urea concentration and 20 g/L. With less than 1 M of ion concentration, the higher the ion concentration in gelling solution, the more the precipitation gets. When the ion concentration is greater than 1 M, due to high ion concentration inhibiting the reaction, there is no obvious increase in calcium precipitation. Therefore, the optimum ion concentration for MICP with Bacillus Megaterium is 0.5–0.75 M. The conclusions lay the ground for subsequent engineering application with Bacillus Megaterium.