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Objectives This study aims the covalent immobilization of Jack bean urease on Fe 3 O 4  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 °C, while the both immobilized urease preparations exhibited their maximal catalytic activities at 70 °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 °C, respectively. The free urease remained 30% of their initial activity at 4 °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@MNPs-ECH may find a potential application area in urea hydrolysis.

Different spacer-arm attached magnetic nanoparticles for covalent immobilization of Jack bean urease