Urease-driven CaCO3 production by Bacillus megaterium RB-05 for application in sand stabilization.

In this study, growth and enzyme production of Bacillus megaterium RB-05 was achieved at varying parameters such as temperature, incubation time, pH, carbon source and nitrogen source. Naturally occurring sand with 97% quartz was utilized as the matrix for bacterial growth and CaCO3 precipitation. The estimation of CaCO3 precipitation was done through gravimetric analysis and CaCO3 deposition was detected through EDX and SEM analysis. Furthermore, sand stabilization was determined through Drained triaxial tests. The results obtained showed maximum bacterial growth and urease activity at pH 7, 350C temperature and 48 h incubation time. Bacteria showed maximum growth with glucose as carbon source however, significant urease activity was observed with both glucose and maltose. Optimum bacterial growth was observed with ammonium chloride as the nitrogen source however, maximum urease activity was observed with ammonium sulphate. CaCO3 precipitation of treated sand showed a linear relation between CaCO3 precipitation with urease production. The EDX and SEM analysis showed CaCO3 deposition between sand particles and on the surface. Furthermore, the stress response of sand showed enhanced sand strength at maximum CaCO3 precipitation. The obtained results show the link between urease production, CaCO3 precipitation, and sand stabilization by MICP. High urease activity influences CaCO3 precipitation in the soil followed by enhanced soil strength. However, the positive results were obtained in reactor environment, further studies are required to make the technique applicable. [ABSTRACT FROM AUTHOR]