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

• MIL-53(Fe) was used for in-situ and covalent binding immobilization of HIL and RML. • The support was synthesized in water and at room temperature for the first time. • High enzyme loading was achieved by in-situ immobilization method. • The immobilized lipases showed the broader temperature and pH profiles. • The HIL@MIL-53(Fe) maintained 95 % of its initial activity after 7 catalytic rounds. 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 °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. [ABSTRACT FROM AUTHOR]