Temperature‐dependent inactivation and catalysis rates of plant‐based ureases for engineered biomineralization

Abstract

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 (kurea) 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.

A Numerical Model for Enzymatically Induced Calcium Carbonate Precipitation

“…This is in agreement with other reports of S. pasteurii not being able to grow above 40 • C [24]. However, while plant-based and S. pasteurii ureases are inactivated at 60 • C, the inactivation is slow enough to allow for significant ureolysis to occur [22,23]. Thus, ureolysis in this experiment was catalyzed predominantly by the residual urease of the inactivated cells, while initially, to some extent, living-cell urea hydrolysis might have occurred although that was not measured.…”

“…Both columns were preheated to 60 • C by placing them in a temperature-controlled oven and kept in the oven for the course of the experiments. Sixty degrees Celsius was determined to be the temperature at which the optimal rate of ureolysis was achieved for the bacterial and plant-based sources of urease under conditions similar to those in the column experiment [22,23]. This temperature is a compromise between a fast ureolysis rate and a relatively low urease inactivation rate, both rates increasing exponentially with temperature according to an Arrhenius-type relationship.…”

“…Thus, when modeling EICP, the key issue is predicting the distribution of ureolytic activity within the porous medium, since urease is the main agent and the prerequisite for EICP. Hence, we focus on modeling the apparent ureolytic activity as measured in the batch experiments along with its increased rate of inactivation at elevated temperatures [22,23].…”

“…The reaction rates for urease-catalyzed ureolysis are modeled to be of first order with respect to urease and urea (substrate) concentration, as suggested by [22,23]; the thermal ureolysis rate is assumed to be of first order with respect to only the urea concentration, inhibited by the presence of Ca 2+ [30]. The rates are as follows:…”

Experimental Methods and Imaging for Enzymatically Induced Calcite Precipitation in a Microfluidic Cell

“…(2020) and Feder et al. (2020). From preliminary batch experiments, we know that right after mixing equal volumes of Solutions 1 and 2 the resulting pH value is around 7.…”