Study of the effect of temperature on microbially induced carbonate precipitation

Temperature is a key factor that contributes to microbially induced calcium carbonate precipitation. At low temperatures, low enzyme activity results in a lack of calcium precipitation. In this study, Sporosarcina pasteurii and Bacillus megaterium were compared. Firstly, the optical density curves and enzyme activity curves of both bacteria were obtained during 48-h culture. Then, optical density, enzyme activity, and productive rates for calcium carbonate were measured to analyze the influence of temperature. Finally, the effect of urea concentration on carbonate precipitation was studied by changing the urea concentration that was added during inoculation. The obtained results showed that at high temperature, the growth rate of B. megaterium was close to that of S. pasteurii, while the opposite result was found at low temperature. The urease activities of B. megaterium were similar at different temperature conditions. At high temperature, B. megaterium showed lower enzyme activity, while at low temperature, it surpassed that of S. pasteurii. The same results were found for enzyme activity and for the precipitation rates of calcium carbonate. The addition of urea to the medium increased precipitation rates, and higher urea concentrations increased the obtained precipitation rates. With 20 g/L urea, the precipitation rate of B. megaterium at 15 °C matched that without urea addition at 30 °C. Therefore, adding urea to the medium at the time of inoculation can effectively overcome the low calcium precipitation at low temperature and enable subsequent low-temperature engineering applications.