Immobilization and Characterization of Naringinase from Aspergillus aculeatus Onto Magnetic Fe3O4 Nanoparticles

In this work, magnetic Fe3O4 nanoparticles were prepared through chemical co-precipitation and used for naringinase immobilization. Magnetic particles were characterized through transmission electron microscopy, Fourier transform infrared spectroscopy, hysteresis loop, and X-ray diffraction analyses. Immobilization was investigated by determining enzyme concentration, glutaraldehyde concentration, immobilization time, temperature, pH, and oscillation speed. Results showed that Fe3O4 nanoparticles exhibited a size of about 15 nm and decreased saturation magnetization value after immobilization. Enzyme activity recovery increased to 31.9% when 0.35 mg/mL enzyme and 3% glutaraldehyde were mixed at pH 5.0 and 28 degrees C for 4 h. The optimal temperature and pH of naringinase were not affected by immobilization. Naringinase-Fe3O4 nanoparticles exhibited higher pH stability than free nanoparticles, but the temperature stability of naringinase decreased after immobilization. The Michaelis constant (Km) indicated that immobilized enzyme presented lower affinity to the binding substrate than free enzymes. The residual enzyme activity was retained at 83% after eight reuse cycles, and immobilized naringinase preserved more than 78% of its original activity after storage for 60 d at 4 degrees C.