Characteristics of immobilized urease onto modified zirconium (IV) oxide via glutaraldehyde: kinetic, stability, and operational stabilities in bioreactors


Alptekin Ö.

CHEMICAL PAPERS, vol.76, no.2, pp.749-761, 2022 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 76 Issue: 2
  • Publication Date: 2022
  • Doi Number: 10.1007/s11696-021-01891-6
  • Title of Journal : CHEMICAL PAPERS
  • Page Numbers: pp.749-761
  • Keywords: Urease, Immobilization, Zirconium (IV) oxide, Operational stability, Bioreactors, JACK BEAN UREASE, THERMAL INACTIVATION, STORAGE STABILITY, CATALASE, SURFACE, MEMBRANE

Abstract

This study aimed to obtain an efficient immobilized urease covalently immobilized onto modified zirconium (IV) oxide (ZrO2) that could serve in a dialysate regeneration system. For the first time, the characteristics of modified ZrO2 and immobilized urease preparations were studied in detail. The operational stabilities of urease in batch and continuous flow-type reactors were also compared. ZrO2 was sequentially modified with Piranha, 3-aminopropyl triethoxysilane, and glutaraldehyde (GA) followed by urease immobilization. The surface area of the carrier was increased by 29% after Piranha treatment. The bound urease onto modified ZrO2 was 3.9 mg g carrier(-1). Optimum pH and temperature of free and immobilized ureases were found as 6.5 and 50 degrees C, and 7.0 and 60 degrees C, respectively. Following immobilization, the K-m value of urease was increased from 2.7 +/- 0.1 to 10.2 +/- 0.4 mM and the V-max value decreased from 51.6 +/- 2.0 to 0.16 + 0.02 U mg protein(-1). The immobilized urease was 62, 35, and 46 fold more stable than the free urease at 50, 60, and 70 degrees C, respectively. It showed 90 and 58% of its initial activity at 4 degrees C and room temperature at the end of 12 days, respectively. The amount of removed urea was found to be 0.22 mg in a batch-type reactor and 0.39 mg in a continuous flow-type reactor at the end of 60 min. The immobilized urease onto ZrO2 has superior potential to use in artificial kidney machines due to significant contribution to reducing device weight.