Characterization of Indigenous Bacteria for Microbially Induced Carbonate Precipitation in a Limestone Mine

Microbially induced carbonate precipitation (MICP) refers to the formation of calcium carbonate driven by microbial metabolic processes, such as ureolysis. As an emerging biocementation technique, MICP has garnered attention for various applications in environmental and civil engineering. This study evaluated the feasibility of MICP implementation in a limestone mine. Ureolytic bacteria were isolated from an active limestone quarry at Mt. Buko, Saitama, Japan. Located at an elevation above 1000 m, the site represents a low-temperature environment with an average annual temperature of ~10 °C. The representative isolates, Rhodococcus sp. strains L6 and L8, exhibited tolerance to key environmental factors relevant to MICP applications in the limestone-rich settings, including alkaline pH, high calcium levels, and elevated urea concentrations. Additionally, both strains were psychrotolerant, maintaining growth and urease activity at temperatures as low as 5 °C. Notably, both strains induced calcite crystal formation at 10 °C and 5 °C, although the reaction was slower at 5 °C. Furthermore, strain L6 demonstrated the ability to induce MICP on limestone surfaces, effectively sealing rock fissures. These findings suggest that indigenous microbes retain metabolic activity in the limestone mine and are well suited for MICP applications.