Covalent binding and in-situ immobilization of lipases on a flexible nanoporous material

In this study, the flexible nanoporous MIL-53(Fe) (MIL = Materials of Institute Lavoisier) was used as an efficient support for in-situ and covalent binding immobilization of Humicola insolens lipase (HIL) and Rhizomucour miehei lipase (RML). In the covalent attachment procedure, the support synthesized under ultrasound irradiation was functionalized by N,N-dicyclohexylcarbodiimide and then attached to the enzyme. In the case of in-situ immobilization method, the support was easily synthesized in water and at room temperature by just replacing terephthalic acid with disodium terephthalate. The in-situ approach was very efficient in terms of enzyme loading, resulting in the immobilization of 66 mg and 81 mg.g(-1) of RML and HIL, respectively, While in the covalent attachment about 15 mg.g(-1) of enzymes were immobilized. Moreover, pH, thermal stability, and reusability of the prepared biocatalysts were investigated. The in-situ immobilization of H. insolens considerably improved its stability compared with covalent attachment even in extreme conditions of temperature (around 100 % of its initial activity at 80 degrees C) and pH (over 90 % at pH 5 and about 100 % at pH 9) and also allowed the enzyme to be reused up to 7 reaction cycles with more than 90 % residual activity.