Abstract: “Microbiological hydrolysis of urea (ureolysis) is a natural geochemical process which is closely linked with carbonate precipitation, or biocalcification. However, for sake of simplicity, ureolysis rate has often been considered to be first order with respect to urea concentration and quantitative role of microorganism remains underestimated. In this study, ureolysis and growth of ureolytic microorganism Bacillus pasteurii has been closely investigated in laboratory batch experiments at three different levels of initial urea and biomass concentration. Results suggest though biomass growth to be independent of initial urea concentration but ureolysis depends on both of the parameters. Experimental data modelling with a number independent rate expressions for biomass growth (i.e. exponential, logistic, Gompretz, modified logistic), ureolysis (1st order, pseudo-first order) as well as coupled (Monod, Contois model), reveals a modified logistic expression for growth and Michaelis–Menten su”

Keywords: ureolysis, modelling, modified logistic, regression