Magnetic nanoparticles prepared in natural deep eutectic solvent for enzyme immobilisation

Abstract

As a new environmentally friendly and sustainable green solvent, deep eutectic solvent (DES) was considered to be the most suitable alternative solvent for ionic liquids, with wide application. In this study, we reported a novel method of the synthesis of Fe3O4 nanoparticles (Nano-Fe3O4) in the natural deep eutectic solvent (NADES) of betaine/urea. Compared with traditional synthetic methods, this method of synthesising magnetic nanoparticles with the NADES as solvent possesses the superiority of mild reaction conditions, no need for nitrogen protection and short time-consuming. The yield of Nano-Fe3O4 synthesised in the NADES was as high as 94.9%. The synthesised Nano-Fe3O4 were coated with silicon and used to immobilise β-glucosidase extracted from Agrocybe aegerit. The results showed that the immobilisation efficiency of the β-glucosidase was 87.5% and the immobilisation yield was 86.2%. The optimum reaction conditions of the immobilised β-glucosidase were 55 °C and pH 6.0. In addition, the thermostability, pH stability and storage stability of the β-glucosidase were greatly improved after its immobilisation on the Nano-Fe3O4. After reused for 10 cycles, the residual activity of the immobilised β-glucosidase was still more than 72.4%. From multiple perspectives, the synthesised Nano-Fe3O4 in the NADES seems to be an excellent carrier for enzyme immobilisation.