Different Spacer-Arm Attached Magnetic Nanoparticles for Covalent Immobilization of Jack Bean Urease

Objectives: This study aims the covalent immobilization of Jack bean urease on Fe3O4 magnetic nanoparticles via glutaraldehyde (urease@MNPs-Si-Glu) and epichlorohydrin (urease@MNPs-ECH) spacer arms. Methods: The optimum pH and temperature, thermal, storage and reuse stability of free and immobilized urease preparations were investigated. Thermodynamics characterizations of free and immobilized urease preparations were also studied. Results: The free urease and both immobilized urease preparations showed maximal catalytic activity at pH 7.5. The free urease had a maximal catalytic activity at 50 degrees C, while the both immobilized urease preparations exhibited their maximal catalytic activities at 70 degrees C. The urease@MNPs-Si-Glu and urease@MNP-ECH showed 2.7- and 1.9-fold higher thermal stability than the free urease at 60 degrees C, respectively. The free urease remained 30% of their initial activity at 4 degrees C, while urease@MNPs-Si-Glu and urease@MNPs-ECH retained 72 and 60% of their initial activities at the same conditions. The urease@MNPs-Si-Glu and urease@MNPs-ECH preserved 53 and 52% of their initial activities, respectively for urea hydrolysis after 20 reuses. Conclusions: The urease@MNPs-Si-Glu and urease@MNPsECH may find a potential application area in urea hydrolysis.