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    Influence of Metal Ions and Organic Solutions on Activity and Stability of Beta-Glucosidase Nanoflowers
    (Wiley-V C H Verlag Gmbh, 2024) Altinkaynak, Cevahir; Samsa, Canan Gulmez; Ekremoglu, Murat; Turk, Merve; Ozturkler, Melek; Ozdemir, Nalan; Atakisi, Onur
    beta-Glucosidase, a pivotal enzyme in the synthesis of various glycosides with wide applications in industries such as food, cosmetics, beverages, bioenergy, nutraceuticals, pharmaceuticals, and detergents, undergoes immobilization to enhance its utility in industrial processes and improve enzymatic properties. In this study, the conventional hybrid nanoflower synthesis method was used for beta-glucosidase-inorganic hybrid nanoflowers. Following a comprehensive pH and temperature scanning of the nanoflowers, the influence of metallic ions and various organic solvents on hybrid nanoflowers to enhance the activity and stability of the biocatalyst were investigated. The optimal morphology for beta-Glu/NFs was determined to be 0.01 mg/mL. To obtain the optimum activity conditions, we explored pH values ranging from 3 to 8 and temperatures between 30 and 80 degrees C. Both the free form and beta-Glu/NFs exhibited higher activity in acidic conditions, with a significant decrease in activity observed at pH 7 and 8. beta-Glu/NFs demonstrated superior activity compared to the free enzyme in the presence of metal ions, exhibiting a remarkable 3.6-fold increase in activity in chloroform, and approximately 2.8 and 2.7 times increase in benzene and glycerol, respectively. Moreover, it displayed over a 2-fold increase in activity in methanol, ethanol, isopropanol, n-butanol, acetone, and DMSO.
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    Peroxidase-like activity of hemoglobin-based hybrid materials against different substrates and their enhanced application for H2O2 detection
    (CHEM SOC ETHIOPIA, 2021) Altinkaynak, Cevahir; Turk, Merve; Ekremoğlu, Murat; Ozdemir, Nalan
    Organic-inorganic hybrid nanoflowers method with unique properties are preferred than conventional immobilization methods for the past decade. Hereemoglobin-based hybrid material (FlbNFs@Cu) was synthesized under different experimental conditions (pH 5.0-9.0 and 0.01-0.50 mgmL(-1) of hemoglobin) obtaining a material size of 9-10 mu m. The encapsulation percentage and weight yield of HbNFs@Cu were determined as 100% and 6.7%, respectively. The peroxidase-like activities of the material against different substrates (ABTS and Guaiacol) were compared to free hemoglobin. The HLINFs@Cu hybrid structure exhibited V-max of 3.6995 EU/mg and a Michaelis-Menten constant (K-M) of 0.1357 mM/mL. The HbNFs@Cu hybrid material was then used to catalyze the oxidation of a peroxidase substrate ABTS to the pigmented product, which provided a colorimetric and spectrophotometric detection of H2O2. The linear operating range, detectable colorimetrically as H2O2 sensor, is 0.005-0.0042 mM, while the linear operating range, detectable spectrometically, is 0.003-0.0042 mM. The limits of detection of colorimetric and spectrophotometric sensors were 0.005 mM and 0.003 mM, respectively. Collectively, these results showed that HLINFs@Cu can be used as colorimetric biosensor for H2O2 in potential applications such as pharmaceutical food, biomedical, environmental, and industrial.