Evaluation of effective factors in biocement production by Bacillus spp. isolated from lime soils of southern Iran

Background & Calcite precipitation by microbial stimulation (MICP) is the new method which used for soil stabilization and solidity. Biocementation is an ecological process based on microbial urease enzyme activity. The present study aimed to isolation and identification of Bacillus spp. with MICP potential from various ecosystems of Iran.Materials & This cross-sectional study was conducted on 200 soil samples collected from arid and desert ecosystems of Iran. Bacillus were isolated and characterized by conventional microbiology tests and molecular methods include the amplification and sequences analysis of gyrA and 16S rRNA genes. Growth in presence of urea, different salinity, pH and temperature, also SEM, XRD and wind tunnel analysis were used to determine biocementation ability. A total of 5 Bacillus isolate with strong urease activity belonging to 4 different species include B. amyloliquefaciens, B. thuringiensis, B. carboniphilus and B. oleos were identified. Optimum conditions for MICP by isolates are 35°C, pH 8.8 and 6% salinity. Moreover, the results of wind tunnel after MICP showed a 100-fold reduction in soil loss at a flow rate of 100 km/h. The results showed that indigenous Bacillus spp. have a significant potential to produce bio-cement. Therefore, its suggest the MICP process have been used to reduce soil losses due to wind erosion, stabilization of loose sands and ground consolidation in the desert soils of the country.