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    Comparative study of ASNase immobilization on tannic acid-modified magnetic Fe3O4/SBA-15 nanoparticles to enhance stability and reusability
    (Royal Soc Chemistry, 2020) Noma, Samir Abbas Ali; Ulu, Ahmet; Acet, Omur; Sanz, Raul; Sanz-Perez, Eloy S.; Odabasi, Mehmet; Ates, Burhan
    In this work, l-asparaginase was immobilized on tannic acid-modified magnetic mesoporous particles. In brief, Fe3O4/SBA-15/tannic acid magnetic particles were synthesized, and their structures and morphologies were fully characterized using various methods. The properties of the free and immobilized enzyme were examined in terms of pH, temperature, thermal stability, storage stability, and reusability. Moreover, the effects of metal ions, inhibitors and organic solvents on the activity of the immobilized enzyme were investigated. Compared to the free enzyme, the immobilized enzyme possessed better tolerance to changes in ambient temperature and pH. Additionally, thermal incubation results showed that the free enzyme lost its activity, while the immobilized enzyme exhibited the opposite behavior. Most strikingly, the immobilized l-asparaginase exhibited a high degree of activity (70%) after being reused 16 times while also demonstrating 71% and 63% storage stability of the initial activity even after 28 days at 4 degrees C and room temperature, respectively. Together with these results, l-asparaginase was successfully immobilized upon Fe3O4/SBA-15/tannic acid magnetic nanoparticles with improved stability properties. This support holds great potential and opens up a novel perspective for growing applications.
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    L-asparaginase immobilized p(HEMA-GMA) cryogels: A recent study for biochemical, thermodynamic and kinetic parameters
    (Elsevier Sci Ltd, 2021) Noma, Samir Abbas Ali; Acet, Omur; Ulu, Ahmet; Onal, Burcu; Odabasi, Mehmet; Ates, Burhan
    Cryogels have recently been attracted intense attention as suitable carriers for enzyme immobilization. Herein, L-asparaginase was selected as the model enzyme due to its application such as pharmaceutical and food. Under optimum conditions, L-asparaginase was immobilized on poly (2-hydroxyethyl methacrylate-glycidyl methacrylate) cryogels with 68.8% of immobilization yield and 69.3% of activity recovery. The immobilized enzyme exhibited improved stability with respect to the soluble enzyme at extreme conditions, especially around acidic pH and high temperature. Also, the storage stability and reusability of the immobilized enzyme were found to be approximately 54% and 52% of the original activity after 28 days at room temperature and 10 cycles, respectively. The thermodynamic studies indicated that activation energy (E-a) of the free enzyme decreased from 13.08 to 10.97 kJ/mol, which means an increase in the thermostability of L-asparaginase. The Michaelis-Menten constants (K-m) of 2.04 and 1.67 mM, and the maximum reaction rates (V-max) of 170.0 and 115.0 mu M min(-1) were estimated for soluble and immobilized L-asparaginase, respectively. These findings demonstrated that the designed cryogels turn out to be a good carrier matrix for L-asparaginase immobilization with high catalytic efficiency and enhanced stability.