Background: Cyclodextrin glucanotransferase (CGTase) from Amphibacillus
sp. NPST-10 was covalently immobilized onto amino-functionalized
magnetic double mesoporous core\u2013shell silica nanospheres
(mag@d-SiO2@m-SiO2-NH2), and the properties of the immobilized enzyme
were investigated. The synthesis process of the nanospheres included
preparing core magnetic magnetite (Fe3O4) nanoparticles, coating the
Fe3O4 with a dense silica layer, followed by further coating with
functionalized or non-functionalized mesoporous silica shell. The
structure of the synthesized nanospheres was characterized using TEM,
XRD, and FT-IR analyses. CGTase was immobilized onto the functionalized
and non-functionalized nanospheres by covalent attachment and physical
adsorption. Results: The results indicated that the enzyme
immobilization by covalent attachment onto the activated
mag@d-SiO2@m-SiO2-NH2, prepared using anionic surfactant, showed
highest immobilization yield (98.1%), loading efficiency (96.2%), and
loading capacity 58 \u3bcg protein [CGTase]/mg [nanoparticles]) which
were among the highest yields reported so far for CGTase. Compared with
the free enzyme, the immobilized CGTase demonstrated a shift in the
optimal temperature from 50\ub0C to 50\u201355\ub0C, and showed a
significant enhancement in the enzyme thermal stability. The optimum pH
values for the activity of the free and immobilized CGTase were pH 8
and pH 8.5, respectively, and there was a significant improvement in pH
stability of the immobilized enzyme. Moreover, the immobilized CGTase
exhibited good operational stability, retaining 56% of the initial
activity after reutilizations of ten successive cycles. Conclusion: The
enhancement of CGTase properties upon immobilization suggested that the
applied nano-structured carriers and immobilization protocol are
promising approach for industrial bioprocess for production of
cyclodextrins using immobilized CGTase