Urease immobilized core–shell magnetic Fe[NiFe]O4/alginate and Fe3O4/alginate composite beads with improved enzymatic stability properties: removal of artificial blood serum urea

Abstract

The present study consists of the preparation of core–shell magnetic carriers with alginate and magnetic nanoparticles (Fe3O4 and Fe[NiFe]O4) using for these carriers (MA—magnetite alginate and NFA—nickel ferrite alginate) for urease encapsulation and removal of urea from artificial blood serum. For this purpose, two different magnetic featured carriers (MA and NFA) were synthesized and urease encapsulation was applied to two of them. For optimization of encapsulated urease systems, the amount of magnetic particles and the amount of enzyme were investigated. For the characterization of encapsulated urease systems, the optimum temperature, optimum pH, thermal stability, pH stability, operational stability, reusability and storage stability parameters were examined. Lineweaver–Burk plots were used to determination the kinetic parameters of encapsulated urease systems. In addition to this, FTIR and SEM analysis were performed for determination of chemical and morphological structures of carriers. Finally, the urea removal performance of urease encapsulated MA beads which have the best activity value and stability was investigated with back loop column system. When evaluated in terms of activity, the magnetic urease encapsulated systems reached 98% activity yield. The Km and Vmax values of free urease were calculated as 0.071 mM and 1.22 U/mg proteins, respectively. Accordingly, the kinetic parameters values of urease encapsulated systems were MA (0.103 mM vs. 1.117 U/mg protein) and NFA (0.101 mM vs. 1.121 U/mg protein). The urease encapsulated systems increased thermal stability (20–80 °C) and pH stability (pH 4–9). The reuse number of urease encapsulated systems reached quite good reusability values as 28 for MA and 27 for NFA compared with literature values.