A biocatalytic system obtained via immobilization of urease onto magnetic metal/alginate nanocomposite: Improving reusability and enhancing stability

Abstract Alginate is a biomaterial that is considered suitable for enzyme immobilization. The biocompatibility and characteristics of the immobilized system can be improved by combining alginate with magnetite Fe3O4 nanoparticles. Therefore, the current study investigated the effect of magnetite Fe3O4 NPs on urease immobilization using different concentrations of magnetite Fe3O4 NPs. The morphological features for alginate/magnetite Fe3O4 NPs before and after immobilization were studied using an SEM, TGA, and FTIR. The reusability, half-life, enzymatic kinetics, and storage stability of the enzyme were all enhanced. The immobilization efficiency was determined to be 91% at optimal conditions. The immobilized urease was reused 20 times and a recovery of 59% of the initial activity. The soluble and immobilized urease was stored at 4 °C for 12 weeks and preserved 13% and 49% of the initial activities, respectively. The optimum pH for soluble and immobilized urease activity was estimated to be 7. The optimum temperature for soluble and immobilized urease activity was found to be 35 °C and 40 °C, respectively. The kinetics parameters showed the Vmax of 4.4 and 3.1 μmol/ml·min and the Km of 49.5 and 54.6 mM for the soluble and immobilized urease, respectively. Immobilized urease had a half-life of 11–20 min. The activation energy (Ea) of immobilized urease was determined to be 32 kJ K−1 mol−1, indicating that a small quantity of energy is required to produce the activated complex of substrate hydrolysis.