Urease immobilization on an ion-exchange textile for urea hydrolysis

Abstract

Ion-exchange textiles are used as organic supports for urease immobilization with the aim of developing reactive fibrous materials able to promote urea removal. A non-woven, polypropylene-based cation-exchange textile was prepared using UV-induced graft polymerization. Urease was covalently immobilized onto the cation-exchange textile using three different coupling agents: N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC), N-cyclohexyl-N′-(b-[N-methylmorpholino]ethyl)carbodiimide p-toluenesulfonate (CMC), and glutaraldehyde (GA). The immobilized biocatalyst was characterized by means of FT-IR spectrometry, SEM micrographs, dependence of the enzyme activity on pH and temperature, and according to the kinetic constants of the free and immobilized ureases. The biotextile prepared with EDC in the presence of N-hydroxysuccinimide performs best. The optimum pH was 7.2 for the free urease and 7.6 for the immobilized ureases. The reactivity was maximal at 45 °C for free urease, 50 °C for biotextiles prepared using EDC or CMC, and 55 °C for biotextiles prepared with GA. The activation energy for the immobilized ureases was 4.73–5.67 kcal mol−1, which is somewhat higher than 4.3 kcal mol−1 for free urease. The urea conversion for a continuous-flow immobilized urease reactor is nearly as good as a continuously stirred tank reactor having a much longer residence time, suggesting that the packed bed reactor had sufficient diffusive mixing and residence time to reach nearly optimal results. Urease immobilized on a biotextile using EDC has good storage and operational stability. Copyright © 2006 Society of Chemical Industry