Utilization of two modified layered doubled hydroxides as supports for immobilization of Candida rugosa lipase.

ABSTRACT

In this study, two synthetic layered doubled hydroxides (LDH), including Mg/Al-CO3-LDH (LDH1) and Zn/Al-CO3-LDH (LDH2), were prepared using the co-precipitation method and modified with sodium dodecyl sulfate to be utilized as carriers for immobilization of Candida rugosa lipase via the adsorption. The activity of prepared biocatalysts was measured in the olive oil hydrolysis. The effects of lipase concentration, pH, storage stability and thermal resistance of the samples were also studied. The maximum activity was obtained at pH 6.0 for immobilized lipase on modified LDHs with monolayer surfactants, including MLDH1 (0.922 U/mg) and MLDH2 (0.744 U/mg), respectively. The remained activities for immobilized lipase on MLDH1 and MLDH2 after 24 h incubation at 60 °C were 85% and 81%, respectively. During the 25days of storage at 4 °C, immobilized lipases on MLDH1, MLDH2, and free lipase kept 87%, 86%, and 70% of their initial activities. The residual activities for immobilized lipase on MLDH1 and MLDH2 after reusing for ten cycles were 72% and 67% of their initial activities. Adsorption parameters for sorption of lipase on all supports were fitted to the Freundlich and Langmuir isotherms. Kinetic parameters obtained from the Michaelis-Menten equation on MLDH1 and MLDH2 were comparable to free enzyme.