Kinetics of calcite precipitation by ureolytic bacteria under aerobic and anaerobic conditions

The kinetics of urea hydrolysis (ureolysis) and induced calcium carbonate (CaCO3) precipitation for engineering use in the subsurface was investigated under aerobic conditions using Sporosarcina pasteurii (ATCC strain 11859) as well as Bacillus sphaericus strains 21776 and 21787. All bacterial strains showed ureolytic activity inducing CaCO3 precipitation aerobically. Rate constants not normalized to biomass demonstrated slightly higher rate coefficients for both ureolysis (kurea) and CaCO3 precipitation (kprecip) for B. sphaericus 21776 (kurea = 0.10 ± 0.03 h-1, kprecip = 0.60 ± 0.34 h-1) compared to S. pasteurii (kurea = 0.07 ± 0.02 h-1, kprecip = 0.25 ± 0.02 h-1) though these differences were not statistically significantly different. B. sphaericus 21787 showed little ureolytic activity but was still capable of inducing some CaCO3 precipitation. Cell growth appeared to be inhibited during the period of CaCO3 precipitation. TEM images suggest this is due to the encasement of cells and...