Urea permeation and hydrolysis through hollow fiber dialyzer immobilized with urease

The surface of commercial polyacrylonitrile hollow fibers was hydrolyzed and covalently bonded with urease by using glutaraldehyde. Mini-modules assembled with these modified hollow fibers were then used to study the effect of concentration of glutaraldehyde, pH, and temperature on the catalysis of urea. The immobilized amount increased with the concentration of glutaraldehyde. However, urease immobilized with 5% glutaraldehyde had higher activity (0.38 μmol/min/mg-urease) than with other concentrations. The activity of the immobilized urease remained at above 0.32 μmol/min/mg-urease over wider applicable ranges of temperature (4–70°C) and pH (5–8) compared to free urease. For comparison, the activity of immobilized urease was 0.35 μmol/min/mg-urease, while that for non-immobilized urease was 0.33 μmol/min/mg-urease at pH 7 and 20°C. The removal of urea using urease-immobilized dialyzer was demonstrated with in-vitro dialysis and showed faster removing rate of urea than a regular dialyzer by 2.7 times.