title: Sol-gel encapsulation of pullulanase in the presence of hybrid magnetic (Fe3O4-chitosan) nanoparticles improves thermal and operational stability.
abstract: Pullulanase was sol-gel encapsulated in the presence of magnetic chitosan/Fe3O4nanoparticles. The resulting immobilized pullulanase was characterized by scanning electron microscopy, vibrating sample magnetometry, Fourier transform infrared spectroscopy and thermogravimetric analysis. The results showed that the addition of pullulanase created a more regular surface on the sol-gel matrix and an enhanced magnetic response to an applied magnetic field. The maximal activity retention (83.9%) and specific activity (291.7 U/mg) of the immobilized pullulanase were observed under optimized conditions including an octyltriethoxysilane:tetraethoxysilane (OTES:TEOS) ratio of 1:2 and enzyme concentration of 0.484 mg/mL sol. The immobilized enzyme exhibited good thermal stability. When the temperature was above 60 °C, the immobilized pullulanase showed significantly higher activity than the free enzyme (p < 0.01); enzyme immobilized by simple sol-gel encapsulation and co-immobilized by crosslinking-encapsulation retained 52 and 69% of their initial activity after 5 h at 62 °C, respectively, compared to 11% for the free enzyme. Moreover, the stability of the pullulanase was improved by crosslinking-encapsulation, as the enzyme retained more than 85 and 81% of its original activity after 5 and 6 consecutive reuses, respectively, compared to 80 and 72% of its original activity for simple sol-gel encapsulated enzymes. This indicated the leakage of enzyme molecules through the pores of the gel was substantially abated by cross-linking. Such immobilized pullulanase provides high stability and ease of enzyme recovery, characteristics that are advantageous for applications in the food industry that involve continuous starch processing.
authors.affiliation: School of Food Science and Technology, Jiangnan University, 1800 Lihu Road, Wuxi, 214122, China.|The State Key Laboratory of Food Science and Technology, Jiangnan University, 1800 Lihu Road, Wuxi, 214122, China.|Synergetic Innovation Center of Food Safety and Nutrition, Jiangnan University, Wuxi, 214122, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Long
authors.affiliation: School of Food Science and Technology, Jiangnan University, 1800 Lihu Road, Wuxi, 214122, China.|The State Key Laboratory of Food Science and Technology, Jiangnan University, 1800 Lihu Road, Wuxi, 214122, China.|Synergetic Innovation Center of Food Safety and Nutrition, Jiangnan University, Wuxi, 214122, China.
authors.forename: Xingfei
authors.initials: X
authors.lastname: Li
authors.affiliation: Key Lab of Carbohydrate Chemistry and Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, 1800 Lihu Road, Wuxi, 214122, Jiangsu, China.
authors.forename: Xiaobei
authors.initials: X
authors.lastname: Zhan
authors.affiliation: School of Food Science and Technology, Jiangnan University, 1800 Lihu Road, Wuxi, 214122, China.|The State Key Laboratory of Food Science and Technology, Jiangnan University, 1800 Lihu Road, Wuxi, 214122, China.|Synergetic Innovation Center of Food Safety and Nutrition, Jiangnan University, Wuxi, 214122, China.
authors.forename: Xueming
authors.initials: X
authors.lastname: Xu
authors.affiliation: School of Food Science and Technology, Jiangnan University, 1800 Lihu Road, Wuxi, 214122, China.|The State Key Laboratory of Food Science and Technology, Jiangnan University, 1800 Lihu Road, Wuxi, 214122, China.|Synergetic Innovation Center of Food Safety and Nutrition, Jiangnan University, Wuxi, 214122, China.
authors.forename: Yaoqi
authors.initials: Y
authors.lastname: Tian
authors.affiliation: School of Food Science and Technology, Jiangnan University, 1800 Lihu Road, Wuxi, 214122, China.|The State Key Laboratory of Food Science and Technology, Jiangnan University, 1800 Lihu Road, Wuxi, 214122, China.|Synergetic Innovation Center of Food Safety and Nutrition, Jiangnan University, Wuxi, 214122, China.
authors.forename: Zhengjun
authors.initials: Z
authors.lastname: Xie
authors.affiliation: School of Food Science and Technology, Jiangnan University, 1800 Lihu Road, Wuxi, 214122, China. fpcenter@jiangnan.edu.cn.|The State Key Laboratory of Food Science and Technology, Jiangnan University, 1800 Lihu Road, Wuxi, 214122, China. fpcenter@jiangnan.edu.cn.|Synergetic Innovation Center of Food Safety and Nutrition, Jiangnan University, Wuxi, 214122, China. fpcenter@jiangnan.edu.cn.
authors.forename: Zhengyu
authors.initials: Z
authors.lastname: Jin
mesh_terms: D048271:Chitosan; D004795:Enzyme Stability; D004800:Enzymes, Immobilized; D005290:Ferric Compounds; D006026:Glycoside Hydrolases; D006863:Hydrogen-Ion Concentration; D058185:Magnetite Nanoparticles; D053768:Metal Nanoparticles; D013696:Temperature
chemical_list: D004800:Enzymes, Immobilized; D005290:Ferric Compounds; D058185:Magnetite Nanoparticles; C000499:ferric oxide; D048271:Chitosan; D006026:Glycoside Hydrolases; C100181:pullulanase
keywords: Immobilization; Magnetic chitosan/Fe3O4 nanoparticle; Pullulanase; Sol–gel encapsulation; Stability