The study of pH, temperature, reusability, and storage stabilty of urease immobilized on electrospun polyacrylonitrile mat

Abstract

The objective of this study was to prepare the urease-immobilized polyacrylonitrile electrospun (ePAN) mats as enzyme-carrying system. Ultrafine beadless microfibrous ePAN mats with average fiber diameter of 1448 ± 380 nm were fabricated by electrostaticly spinning of 10 wt % PAN in DMF dope solution. Urease was then covalently immobilized on the surface of ePAN mats following the treatment with ethylenediamine (EDA) and different concentrations of glutaraldehyde (GA). The surface chemistry of as-spun and chemically treated fibers was examined with Fourier transform Infrared (FTIR) spectroscopy. Field Emission Scanning Electron Microscopy (FESEM) was used to study and examine the changes in the morphology and diameter of the pristine, chemically treated, and ureaseimmobilized microfibrous mats. The properties of the immobilized urease were assayed. It was found that urease immobilized on 5 % GA treated ePAN mats retained the highest activity of 54 % with 157 ug enzyme immobilized per mg mat. In addition, it was observed that immobilization altered the pH and temperature of the maximum activity from 7 to 7.5 and 37°C to 50 °C for free and immobilized urease, respectively. The kinetic parameters of the free and immobilized urease, Km and Vm, were also evaluated with an observed increase in Km and decrease in Vm following the immobilization of enzyme on the surface of ePAN fibers. Besides, immobilization procedure proved its success in terms of preserving near 70 % of initial activity of the immobilized urease even after 15 cycles of reuse. In conclusion, the results of this work open a promising avenue for covalent immobilization of different enzymes on nano to microfibrous mats. The urease immobilized ePAN fibers may possibly find application in efficient removal of urea from valuable dialysate solution in hemodialysis apparatus.