Salt tolerance domestication of urease bacteria for biocementation

In engineering practice of microbial-induced carbonate precipitation (MICP), urease-producing bacteria (UPB) cannot tolerate high-salt concentrations of cementation solution (CS). Increasing the salt tolerance of UPB to CS can improve the efficiency and the application scope of MICP. In order to enhance the salt tolerance of Sporosarcina pasteurii, a gradual salt concentration gradient method was employed for its domestication. Growth characteristics in the domestication medium were evaluated through optical density tests, revealing a slowed growth rate in domesticated bacteria. Furthermore, salt tolerance tests, unconfined compressive strength (UCS) tests, and scanning electron microscopic analyses were conducted to investigate the calcium ion precipitation capacity, strength properties of bio-cemented sand columns, and microstructure of reinforced samples among untamed bacteria (UB), domesticated bacteria (DB), and the control group. The results indicate the following: DB's tolerance to CS salt concentration exhibited an approximate increase of 0.25 mol/L. In the context of high concentration CS conditions, DB-treated samples demonstrated approximately double the UCS in comparison to UB, indicating a more efficient calcium ion precipitation process. Furthermore, DB resulted in a higher proportion of cauliflower-like calcium carbonate crystals under high concentration CS conditions. This crystal morphology is commonly associated with superior mechanical properties. These findings demonstrate that domestication effectively enhances bacterial biomineralization performance in high-salinity environments.