Hyperactivation of lipases by immobilization on superhydrophobic graphene quantum dots inorganic hybrid nanoflower

Abstract

Various nanoflowers are synthesized for enzyme immobilization. In order to increase the activity of nanoflowers, in this study, 3D flower-like structured organic–inorganic hybrid nanoflowers (hNFs) with various lipases Rhizomucor miehei lipase (RML), Candida antarctica lipase B (CALB), Humicola insolens lipase (HIL), Thermomyces lanuginosus lipase (TLL), Eversa® Transform 2.0 (ET) a genetically modified enzyme derived of TLL and graphene quantum dots (GQDs) were prepared and characterized.Lipase hNFs [lipase-(Cu/Co)3(PO4)2] and lipase@GQDs hNFs [lipase@GQDs-(Cu/Co)3(PO4)2] were straightforwardly prepared through mixing with metal ion (Cu2+or Co2+) aqueous solutions with or without GQDs. The ET@GQDs-(Cu)3(PO4)2 hNFs demonstrated 687 % higher activity than ET-(Cu)3(PO4)2 hNFs and 650 % higher activity than the free ET. Similar results were also observed with other lipase hybrid nanoflowers. For example, TLL@GQDs-(Cu)3(PO4)2 hNFs exhibited a 557 % higher activity than TLL-(Cu)3(PO4)2 hNFs and a 463 % higher activity than free TLL. Additionally, TLL@GQDs-(Co)3(PO4)2 hNFs showed a 141 % higher activity than TLL-(Co)3(PO4)2 hNFs and a 304 % higher activity than free TLL. Upon examining pH and thermal stability, it was revealed that lipase@GQDs hNFs exhibited higher activity compared to free lipase and other hNFs without GQDs. The effect of metal ions, enzyme concentrations and amount of GQDs on the morphology and enzyme activity of the lipase-hNFs was examined.