Engineered ureolytic Bacillus subtilis and its future in Microbial Induced Calcium Carbonate Precipitation (MICCP)

As the global population grows there is an urgent need for increased, yet sustainable civil infrastructure. The ability to harness biological processes in order to improve ground stability; as well as creating construction materials without adding to climate damage is necessary. In almost every environment on earth, microorganisms and microbially mediated mineralisation (biomineralisation) processes are active. It is well documented that microbes present in soil can induce the precipitation of calcium carbonate (CaCO3) in both the laboratory and the natural setting through microbial induced calcium carbonate precipitation (MICCP). MICCP utilises microorganisms as a result of their active metabolism, to precipitate CaCO3, strengthening the surrounding matrix. MICCP is used in a variety of different applications such as carbon sequestration, environmental remediation and improving construction materials.

The enzyme urease catalyzes the hydrolysis of urea to ammonia and CO2, and is acknowledged to be instrumental in MICCP. Bacillus subtilis is a model, gram positive, spore-forming soil bacterium that produces a functionally active urease, but with low efficiency, and the activation is not completely understood. Sporosarcina pasteurii is one of the most commonly used MICCP microbes as its urease operon has been well studied and the bacterium has proven to produce ecologically stable bioconstruction materials. The ability to clone the urease operon of S. pasteurii into the model B. subtilis would create an engineered ureolytic organism whose urease activity could be controlled. This control would enable the CaCO3 morphology and material properties to be tailored and would create a truly responsive biomaterial.