Characterization of ureolysis and microbially induced calcium carbonate precipitation under different incubation and reaction conditions

Abstract

Understanding the factors influencing ureolysis and calcium carbonate precipitation is essential for optimizing microbially induced calcium carbonate precipitation (MICP) processes, yet comparative insights into different bacterial species under varying conditions remain inconclusive. This study investigates the ureolysis and MICP characteristics of Sporosarcina pasteurii and Lysinibacillus sphaericus under varying incubation and reaction conditions. Batch experiments were conducted to assess the effects of incubation duration and pH, bacterial cell density, and reagent (i.e., urea and calcium ion) concentrations on ureolysis and CaCO₃ precipitation. The findings indicate that both bacteria exhibit higher urease activity after 24 h of incubation compared to 48 h, regardless of incubation pH. S. pasteurii exhibits maximum specific urease activity when incubated at an alkaline pH (pH 9.0), whereas L. sphaericus peaks after incubation at a neutral pH (pH 7.2). Moreover, the ureolysis performance of S. pasteurii shows greater sensitivity to incubation conditions, while L. sphaericus maintains consistently. At low cell density (OD₆₀₀ ∼0.1), specific urease activity and early-stage mineralization efficiency are improved, whereas high density (OD₆₀₀ ∼1.0) enhances overall CaCO₃ precipitation and prolonged vaterite presence. High reagent concentrations (1.0 and 1.5 M) further enhance urease activity and precipitation rates and lead to vaterite dominance (> 93 %), while low concentration (0.3 M) favors calcite formation over time. These findings provide insights into evaluating and optimizing MICP performance under varying incubation and reaction conditions.