Improvement of sand consolidation, compressive strength of mortar and absorption reduction of water using CaCo3 - precipitating bacteria

The ureolytic bacterial isolate ALEX1 able to precipitate CaCO3 was isolated from a local urea-rich soil. Due to it's a relatively high urease activity, isolate ALEX1 was tested for its ability to improve consolidation of sand, compressive strength of mortar and absorption reduction of water. The data revealed that the highest values of compressive strength and reduction of water absorption were 16.53% and 88.59%, respectively. Identification techniques showed that isolate ALEX1 is a Bacillus cereus strain. Its urease pure enzyme showed a maximum activity at a reaction pH of 7.0, and a relatively high activity in a pH range of 7.0 to 8.0. The enzyme was stable at heat treatment up to 60 degrees C. The amino acids composition of the purified enzyme showed that aspartic was the major amino acid followed by leucin, arginine and glutamic. The results indicate possibility of using Bacillus cereus cells in bioremediation and self-healing of soils.