Uncovering the Dynamics of Urease and Carbonic Anhydrase Genes in Ureolysis, Carbon Dioxide Hydration, and Calcium Carbonate Precipitation.

The hydration of CO 2 suffers from kinetic inefficiencies that make its natural trapping impractically sluggish. However, CO 2 -fixing carbonic anhydrases (CAs) remarkably accelerate its equilibration by 6 orders of magnitude and are, therefore, "ideal" catalysts. Notably, CA has been detected in ureolytic bacteria, suggesting its potential involvement in microbially induced carbonate precipitation (MICP), yet the dynamics of the urease (Ur) and CA genes remain poorly understood. Here, through the use of the ureolytic bacterium Sporosarcina pasteurii , we investigate the differing role of Ur and CA in ureolysis, CO 2 hydration, and CaCO 3 precipitation with increasing CO 2(g) concentrations. We show that Ur gene up-regulation coincides with an increase in [HCO 3 - ] following the hydration of CO 2 to HCO 3 - by CA. Hence, CA physiologically promotes buffering, which enhances solubility trapping and affects the phase of the CaCO 3 mineral formed. Understanding the role of CO 2 hydration on the performance of ureolysis and CaCO 3 precipitation provides essential new insights, required for the development of next-generation biocatalyzed CO 2 trapping technologies.