title: Immobilization of Aspergillus oryzae β galactosidase on zinc oxide nanoparticles via simple adsorption mechanism.
abstract: The present study demonstrates the immobilization of Aspergillus oryzae β galactosidase on native zinc oxide (ZnO) and zinc oxide nanoparticles (ZnO-NP) by simple adsorption mechanism. The binding of enzyme on ZnO-NP was confirmed by Fourier transform-infrared spectroscopy and atomic force microscopy. Native ZnO and ZnO-NP showed 60% and 85% immobilization yield, respectively. Soluble and immobilized enzyme preparations exhibited similar pH-optima at pH 4.5. ZnO-NP bound β galactosidase retained 73% activity at pH 7.0 while soluble and ZnO adsorbed enzyme lost 68% and 53% activity under similar experimental conditions, respectively. There was a marked broadening in temperature-activity profile for ZnO-NP adsorbed β galactosidase; it showed no difference in temperature-optima between 50°C and 60°C. Moreover, ZnO-NP adsorbed β galactosidase retained 53% activity after 1h incubation with 5% galactose while the native ZnO- and soluble β galactosidase exhibited 35% and 28% activity under similar exposure, respectively. Native ZnO and ZnO-NP adsorbed β galactosidase retained 61% and 75% of the initial activity after seventh repeated use, respectively. It was noticed that 54%, 63% and 71% milk lactose was hydrolyzed by soluble, ZnO adsorbed and ZnO-NP adsorbed β galactosidase in batch process after 9h while whey lactose was hydrolyzed to 61%, 68% and 81% under similar experimental conditions, respectively. In view of its easy production, improved stability against various denaturants and excellent reusability, ZnO-NP bound β galactosidase may find its applications in constructing enzyme-based analytical devices for clinical, environmental and food technology.
authors: Department of Biochemistry, Faculty of Life Sciences, Aligarh Muslim University, Aligarh 202002, India. qayyumbiochem@gmail.com
authors: Qayyum
authors: Q
authors: Husain
authors: Shakeel Ahmed
authors: SA
authors: Ansari
authors: Fahad
authors: F
authors: Alam
authors: Ameer
authors: A
authors: Azam
mesh_terms: D000327:Adsorption; D001236:Aspergillus oryzae / Q000201:enzymology*; D004800:Enzymes, Immobilized / Q000737:chemistry / Q000302:isolation & purification*; D006863:Hydrogen-Ion Concentration; D053768:Metal Nanoparticles / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature; D015034:Zinc Oxide / Q000737:chemistry; D001616:beta-Galactosidase / Q000737:chemistry / Q000302:isolation & purification*
chemical_list: D004800:Enzymes, Immobilized; D001616:beta-Galactosidase; D015034:Zinc Oxide