An Improved Method for Determining Urease Activity from Electrical Conductivity Measurements

We present an improved approach to evaluating the activity of urease from electrical conductivity (EC) measurements. In this approach, chemical equilibrium modeling via PHREEQC is used in conjunction with empirical equations for computing EC to develop a function that relates the increase in EC during urea hydrolysis in a closed reactor to the concentration of ammonium species present (and concentration of urea remaining) in the reaction solution. By applying this function to data from continuous measurement of EC during urea hydrolysis, we obtain a profile of the concentration of the urea substrate with time, which is then used to determine the urease activity. The activity of commercially available urease extracted from jack beans was determined using this method and compared well to the activity determined using Nessler's reagent, a commonly used colorimetric assay. This EC-based method is inexpensive and can be used for accurate determination of urease activity for a variety of applications.

Automated summary

We propose an improved method for evaluating urease activity using electrical conductivity (EC) measurements. By combining chemical equilibrium modeling and empirical equations, we develop a function that relates the increase in EC during urea hydrolysis to the concentration of ammonium species and remaining urea. This function is applied to continuously measured EC data to determine the concentration profile of urea with time, allowing for accurate determination of urease activity. The method was compared to a colorimetric assay and showed promising results, making it a cost-effective and accurate option for evaluating urease activity.