Biocement-producing bacteria have the potential to enhance cement manufacturing and repair, but growing these microbes on-site remains a challenge. Now, researchers reporting in ACS Applied Materials & Interfaces have developed a freeze-drying method that preserves the bacteria, potentially allowing construction workers to simply mix powder from a packet with a few raw materials to create biocement.
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This approach could streamline processes like tile-making, oil well repair, and soil stabilization for temporary roads or camps.
Soil stabilization and concrete repair pose significant challenges for civil engineers. In recent years, researchers have explored the use of Sporosarcina pasteurii, a bacterium that facilitates biocement production by breaking down urea into ammonium and carbonate. When calcium is introduced, the reaction forms calcium carbonate, which helps bind sand and soil particles together or fills cracks in existing concrete.
Currently, producing biocement requires specialized equipment and expertise to cultivate the bacteria on-site. To make the process more accessible, Maneesh Gupta and colleagues developed a shelf-stable version of S. pasteurii that construction workers could use without technical training.
Drawing from freeze-drying techniques used in fertilizers, the team suspended S. pasteurii in various solutions to determine which offered the best protection against freezing. They found that sucrose was the most effective. After freezing and drying, the bacteria were stored in resealable plastic bags, where they remained viable for at least three months.
In laboratory tests, the freeze-dried bacteria successfully produced biocement in 3D-printed cylindrical molds filled with play sand—similar to what’s found in children’s sandboxes—or natural sandy soil.
The biocement formed in play sand was stronger and more easily removed from molds compared to that formed in natural soil. In another test, researchers packed the bacteria and soil into PVC pipes and sprayed them with calcium chloride and urea. Over time, repeated applications of the solution increased the strength of the biocement.
To assess their performance in real-world conditions, researchers applied the freeze-dried microbes to 3-by-3-foot (1-by-1-meter) plots of ground and sprayed the surface with calcium chloride and urea. Within 24 hours, the top three inches (7.6 cm) of soil had significantly strengthened.
While further research is needed, this study marks the first demonstration that freeze-dried S. pasteurii can remain viable and effectively produce biocement. If scaled up, this technique could provide a practical, easy-to-use solution for construction and infrastructure projects.
Journal Reference:
Tuttle, M. J., et al. (2025) Shelf-Stable Sporosarcina pasteurii Formulation for Scalable Laboratory and Field-Based Production of Biocement. ACS Applied Materials & Interfaces. doi.org/10.1021/acsami.4c15381.