The magnetic particle Fe 3 O 4 -SiO 2 -NH 2 -Cellu-ZIF8 (FSNCZ8) was used to immobilize the high-temperature resistant GH3 β-glucosidase (Tpebgl3) from the Thermomotoga petrophila DSM 13995. The Tpebgl3 has great potential in the catalytic conversion of pharmaceutically active components. The magnetic carrier (FSNCZ8) which provided stronger adsorption capacity, magnetic and high-temperature stability than the previously discussed Fe 3 O 4 -NH 2 -Cellu-ZIF8 without tetraethyl silicate coated. The properties of FSNCZ8-Tpebgl3 (FSNCZ8-T) were as follows: The optimal temperature and pH were 90 °C and 5.5, respectively; the highest activity of FSNCZ8-T approached 2672 U/g; Fe 2+ enabled immobilized enzyme to increase its relative activity to 194%. The main characteristics of FSNCZ8-T, including thermal stability, pH stability, and glucose tolerance, were greatly enhanced by adding Fe 2+ , which was also superior to free enzymes; moreover, the residual activity of FSNCZ8-T was 74% of the initial activity at the end of 10 repeated cycles.
Jin Xu,Xuejia Shi,Xiaomeng Zhang,Zhenzhong Wang,Wei Xiao,Linguo Zhao
To efficiently recycle GH78 thermostable rhamnosidase (TpeRha) and easily separate it from the reaction mixture and furtherly improve the enzyme properties, the magnetic particle Fe 3 O 4 -SiO 2 -NH 2 -Cellu-ZIF8 (FSNcZ8) was prepared by modifying Fe 3 O 4 -NH 2 with tetraethyl silicate (TEOS), microcrystalline cellulose and zinc nitrate hexahydrate. FSNcZ8 displayed better magnetic stability and higher-temperature stability than unmodified Fe 3 O 4 -NH 2 (FN), and it was used to adsorb and immobilize TpeRha from Thermotoga petrophilea 13995. As for properties, FSNcZ8-TpeRha showed optimal reaction temperature and pH of 90°C and 5.0, while its highest activity approached 714 U/g. In addition, FSNcZ8-TpeRha had better higher-temperature stability than FN. After incubation at 80°C for 3 h, the residual enzyme activities of FSNcZ8-TpeRha, FN-TpeRha and free enzyme were 93.5%, 63.32%, and 62.77%, respectively. The organic solvent tolerance and the monosaccharides tolerance of FSNcZ8-TpeRha, compared with free TpeRha, were greatly improved. Using naringin (1 mmol/l) as the substrate, the optimal conversion conditions were as follows: FSNcZ8-TpeRha concentration was 6 U/ml; induction temperature was 80°C; the pH was 5.5; induction time was 30 min, and the yield of products was the same as free enzyme. After repeating the reaction 10 times, the conversion of naringin remained above 80%, showing great improvement of the catalytic efficiency and repeated utilization of the immobilized α-L-rhamnosidase.
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