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.