Comparative studies on ZIF-8 and SiO₂ nanoparticles as carrier for immobilized β-glucosidase

The immobilization of enzyme is an important biotechnology in industry. Enzyme immobilization by nanomaterials has attracted interest of researchers due to potentially promising application. Many enzymes had been successfully immobilized by different nanomaterials. In this work, β-glucosidase was immobilized by SiO 2 nanoparticles (nano-SiO 2 ) and zeolitic imidazolate framework-8 (ZIF-8), then the enzymatic properties of them were also compared. The nano-SiO 2 @β-glucosidase and the β-glucosidase@ZIF-8 achieved immobilization yield of 58.5% and 23.0%, respectively. Optimal temperature of the free β-glucosidase, nano-SiO 2 @β-glucosidase and the β-glucosidase@ZIF-8 were around 50 °C. Both free β-glucosidase and nano-SiO 2 @β-glucosidase showed maximal catalytic activity at pH 6.0, while the optimal pH of the β-glucosidase@ZIF-8 was 5.4 roughly. The nano-SiO 2 @β-glucosidase exhibited similar pH stability and thermal stability to those of the free β-glucosidase, and the β-glucosidase@ZIF-8 improved pH stability greatly. Moreover, after the treatment of trypsin for 4 h at 37 °C, the residual activities of the β-glucosidase@ZIF-8 was the highest that retained 94%, which provided huge potential for the application of the β-glucosidase@ZIF-8 in industry. Furthermore, the nano-SiO 2 @β-glucosidase and the β-glucosidase@ZIF-8 can be reused for 5 cycles with 87.5% and 88.7% residual activity, respectively.