Weathering and Coupled Mineralization of Serpentine by Urease Gene Overexpression Strain

Urease, a metalloenzyme widely present in various organisms, catalyzes the hydrolysis of urea to ammonia and CO2 and has been extensively utilized in studies and applications of microbially induced calcium carbonate precipitation (MICP). While microbially induced calcium carbonate precipitation (MICP) and silicate mineral bio-weathering are both important biogeochemical processes mediated by microorganisms, and their coupling has been verified in some geological environments, the potential role of urease (a key enzyme in MICP) in mineral weathering remains unreported. In this study, Bacillus velezensis LB002 served as the urease gene donor for the construction of a Bacillus subtilis strain with heterologous overexpression of urease genes. The effects of this engineered strain and the wild-type strain on serpentine weathering and secondary mineral formation were compared. The results showed that the urease activity of the overexpression strain was approximately 3.8 times higher than that of the wild-type strain, and the release of Mg2+ during serpentine weathering increased by 17 mg/L. XRD and SEM-EDS analyses revealed that the wild-type strain promoted the formation of vaterite as a secondary mineral, whereas the overexpression strain induced the precipitation of both vaterite and magnesium-containing calcite. These findings demonstrate that urease plays a synergistic role in mineral weathering and that urease overexpression significantly enhances the release of Mg2+ from serpentine and the formation of magnesium-containing calcite.