Microbial induced calcite precipitation (MICP) potential of ureolytic Bacillus sp. isolated from the soil of eroded ecosystems for stabilizing and improving the fertility of eroded soils

BACKGROUND AND ABJECTIVEThe loss of soil from lands due to erosion has a negative effect on ecosystems and food security. Bacillus due to high catabolic capability is an appropriate candidate for application in biocementation process. The aim of this study is isolate and characterize Bacillus sp. with biocementation capability from various ecosystems.MATERIALS AND METHODSThe isolates were separated from ۴۰۰ samples, and characterized by biochemical and molecular methods include the amplification and sequencing analysis of gyrA and ۱۶S rRNA genes. Growth in presence of urea, in different salinity, pH and temperature, also scanning electron microscope (SEM), X-ray diffraction (XRD) and wind tunnel analysis were applied to determine biocementation ability.RESULTS AND DISCUSSIONA total number of ۱۹۵ isolates were recovered from environmental samples, of which ۲۵ isolates (۱۲.۸۲%) were identified as urease-positive Bacillus which belonged to ۱۰ species consisting of B. subtilis ۵ strains (۲۰%), B. vallismortis and B. seohaeanensis ۴ strains (۱۶%) each, B. mobilis, B. pseudofirmus, B. cohnii, B. cereus, B. alkalinitrilicus ۲ strains (۸%) each, and B. sphaericus and B. megaterium ۱ strains (۴%) each. Moreover, ۱۵ urease- positive isolates (۷.۷%) belonging to Ralostenia, Actinomycete and Halomonas genera were identified. Optimum conditions for microbial induced calcite precipitation (MICP) by isolates are ۳۰°C, pH ۹ and ۶% salinity. The highest rate of calcium carbonate formation and urease activity recorded in B. subtilis with ۲۴.۱۵ mg/mL of calcium carbonate and ۴.۴۰ × ۱۰۳ unit/L of urease, followed by B. mobilis and B. alkalinitrilicus with ۲۲.۸۵ mg/mL of calcium carbonate and ۳.۹۳ × ۱۰۳ unit/L of urease. After MICP the lowest soil loss ratio at a flow rate of ۹۰ km/h, was observed in B. subtilis ۱۰۰-fold reduction, followed by B. seohaeanensis, B. cereus, B. vallismortis, with ۹۰,۸۵,۸۰ folds reduction respectively.CONCLUSIONResults indicate that the diversity of Bacillus sp. offers the potential ability for adaptation to harsh and untapped environment, also showed that the use of MICP on the soil surface can have a very significant role on reducing soil losses due to wind erosion.

کلیدواژه ها:

MICP ، Urease Positive Bacillus ، Soil Erosion ، Biocementation