Microbially Induced Calcite Precipitation Employing Environmental Isolates

Area of Science:

• Geotechnical Engineering
• Microbiology
• Biomineralization

Background:

• Calcite precipitation is a key process in soil improvement.
• Microbial-induced calcite precipitation (MICP) offers a sustainable method for soil stabilization.
• Understanding factors influencing MICP is crucial for its effective application.

Purpose of the Study:

• To evaluate the efficacy of selected microbes in precipitating calcite in cohesionless soils.
• To investigate the influence of soil relative density on the amount of calcite precipitated.
• To assess the correlation between microbial urease activity and calcite precipitation.

Main Methods:

• Five distinct microbial strains, including *Sporosarcina pasteurii* ATCC 11859, were utilized.
• Microbes and a urea-CaCl₂ medium were injected multiple times into cohesionless soils at 60% and 80% relative densities.
• Calcite precipitation was quantified to determine the effectiveness of the process.

Main Results:

• The relative density of cohesionless soils was found to significantly influence the extent of calcite precipitation.
• Four selected microbes exhibited higher urease activities compared to the control strain, *S. pasteurii*.
• A weak correlation was observed between microbial urease activity and the amount of calcite precipitated.

Conclusions:

• Microbial calcite precipitation is feasible in cohesionless soils.
• Soil relative density is a critical factor governing the success of MICP.
• While urease activity is important, it does not solely determine the efficiency of calcite precipitation in this context.