Immobilization of β-galactosidase from Lactobacillus plantarum HF571129 on ZnO nanoparticles: characterization and lactose hydrolysis.

Abstract

β-Galactosidase from Lactobacillus plantarum HF571129 was immobilized on zinc oxide nanoparticles (ZnO NPs) using adsorption and cross-linking technique. Immobilized β-galactosidase showed broad-spectrum pH optima at pH 5-7.5 and temperature 50-60°C. Fourier transform infrared spectroscopy (FTIR) and field emission scanning electron microscopy (FESEM) showed that β-galactosidase successfully immobilized onto supports. Due to the limited diffusion of high molecular weight substrate, K m of immobilized enzyme slightly increased from 6.64 to 10.22mM, while V max increased from 147.5 to 192.4µmolmin(-1)mg(-1) as compared to the soluble enzyme. The cross-linked adsorbed enzyme retained 90% activity after 1-month storage, while the native enzyme showed only 74% activity under similar incubation conditions. The cross-linked β-galactosidase showed activity until the seventh cycle and maintained 88.02% activity even after the third cycle. The activation energy of thermal deactivation from immobilized biocatalyst was 24.33kcal/mol with a half-life of 130.78min at 35°C. The rate of lactose hydrolysis for batch and packed bed was found to be 0.023 and 0.04min(-1).