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.

摘要

作为一种新型环保、可持续的绿色溶剂，深共熔溶剂（DES）被认为是离子液体最合适的替代溶剂，应用广泛。在这项研究中，我们报道了一种在甜菜碱/尿素的天然低共熔溶剂 (NADES) 中合成 Fe ₃ O ₄纳米颗粒 (Nano-Fe ₃ O _{4 ) 的新方法。}与传统合成方法相比，这种以NADES为溶剂合成磁性纳米粒子的方法具有反应条件温和、无需氮气保护、耗时短等优点。在NADES中合成的Nano-Fe ₃ O ₄的收率高达94.9%。合成的纳米铁₃ O ₄被硅包被并用于固定从杨树菇中提取的β-葡萄糖苷酶。结果表明，β-葡萄糖苷酶的固定化率为87.5%，固定化率为86.2%。固定化β-葡萄糖苷酶的最佳反应条件为55 ℃和pH 6.0。此外，β-葡萄糖苷酶固定在纳米Fe ₃ O ₄上后，其热稳定性、pH稳定性和储存稳定性都有很大的提高。重复使用10个循环后，固定化β-葡萄糖苷酶的残留活性仍大于72.4%。从多个角度，合成的纳米Fe ₃ O ₄NADES 似乎是酶固定的极好载体。