Enzymatically induced calcium carbonate precipitation (EICP) is an emerging engineered mineralization method similar to others such as microbially induced calcium carbonate precipitation (MICP). EICP is advantageous compared to MICP as the enzyme is still active at conditions where microbes, e.g., Sporosarcina pasteurii, commonly used for MICP, cannot grow. Especially, EICP expands the applicability of ureolysis-induced calcium carbonate mineral precipitation to higher temperatures, enabling its use in leakage mitigation deeper in the subsurface than previously thought to be possible with MICP. A new conceptual and numerical model for EICP is presented. The model was calibrated and validated using quasi-1D column experiments designed to provide the necessary data for model calibration and can now be used to assess the potential of EICP applications for leakage mitigation and other subsurface modifications.

Engineered (bio)mineralization uses the enzyme urease to catalyze the hydrolysis of urea to promote carbonate mineral precipitation. The current study investigates the influence of temperature on ureolysis rate and degree of inactivation of plant‐sourced ureases over a range of environmentally relevant temperatures. Batch experiments at 30°C demonstrated that jack bean meal (JBM) has a 1.7 to 56 times higher activity (844 μmol urea hydrolyzed g⁻¹ JBM min⁻¹) than the other tested plant‐sourced ureases (soybean, pigeon pea and cottonseed). Hence, ureolysis and enzyme inactivation rates were evaluated for JBM at temperatures between 20°C and 80°C. A combined first‐order urea hydrolysis and first‐order enzyme inactivation model described the inactivation of urease over the investigated range of temperatures. The temperature‐dependent rate coefficients (k_urea) increased with temperature and ranged from 0.0018 at 20°C to 0.0249 L g⁻¹ JBM min⁻¹ at 80°C; JBM urease became ≥50% inactivated in as little as 5.2 minutes at 80°C and in as long as 2238 minutes at 50°C. The combined urea hydrolysis kinetics and enzyme inactivation model provides a mathematical relationship useful for the design of biomineralization technologies and can be incorporated into reactive transport models.

Aims Development of biomineralization technologies has largely focused on microbially induced carbonate precipitation (MICP) via Sporosarcina pasteurii ureolysis; however, as an obligate aerobe, the general utility of this organism is limited. Here, facultative and anaerobic haloalkaliphiles capable of ureolysis were enriched, identified and then compared to S. pasteurii regarding biomineralization activities. Methods and Results Anaerobic and facultative enrichments for haloalkaliphilic and ureolytic micro‐organisms were established from sediment slurries collected at Soap Lake (WA). Optimal pH, temperature and salinity were determined for highly ureolytic enrichments, with dominant populations identified via a combination of high‐throughput SSU rRNA gene sequencing, clone libraries and Sanger sequencing of isolates. The enrichment cultures consisted primarily of Sporosarcina‐ and Clostridium‐like organisms. Ureolysis rates and direct cell counts in the enrichment cultures were comparable to the S. pasteurii (strain ATCC 11859) type strain. Conclusions Ureolysis rates from both facultatively and anaerobically enriched haloalkaliphiles were either not statistically significantly different to, or statistically significantly higher than, the S. pasteurii (strain ATCC 11859) rates. Work here concludes that extreme environments can harbour highly ureolytic active bacteria with potential advantages for large scale applications, such as environments devoid of oxygen. Significance and Impact of the Study The bacterial consortia and isolates obtained add to the possible suite of organisms available for MICP implementation, therefore potentially improving the economics and efficiency of commercial biomineralization.