Enhancing Microbially-Induced Calcite Precipitation (MICP) Using Protein and Peptide Additives

Sporosarcina pasteurii is a soil bacterium capable of cementing soils using an enzymatic reaction that hydrolyzes urea into ammonium and bicarbonate ions. The elevated pH caused by ammonia accumulation causes calcium ions to interact with carbonate to form a crystalline precipitate (calcite). These crystals can form bridges between soil particles, resulting in high-strength biocement. This processes is known as microbially induced calcite precipitation (MICP). Cementation by S. pasteurii in this manner shows promise for the erection of cemented structures in an environmentally-friendly, non-energy-intensive manner. Features of the cementation process include an aqueous reaction environment and harnessing of microbial activity from native soil microbes. At the Air Force Research Laboratory, we are employing microbial and protein engineering strategies to enhance MICP for the production of biocements. This presentation details our efforts using recombinant proteins to assist with calcite nucleation and promotion of desirable crystal morphology to reduce the amount of urea required and to improve the mechanical properties of the material.