Preparation of ion-exchange supports via activation of epoxy-SiO2 with glycine to immobilize microbial lipase - Use of biocatalysts in hydrolysis and esterification reactions.

Ion-exchange supports have been prepared via sequential functionalization of silica-based materials with (3‑Glycidyloxypropyl)trimethoxysilane (GPTMS) (Epx-SiO2) and activation with glycine (Gly-Epx-SiO2) in order to immobilize lipase from Thermomyces lanuginosus (TLL) via adsorption. Rice husk silica (RHS) was selected as support with the aim of comparing its performance with commercial silica (Immobead S60S). Sequential functionalization/activation of SiO2-based supports has been confirmed by AFM, SEM and N2 adsorption-desorption analyses. Maximum TLL adsorption capacities of 14.8 ± 0.1 mg/g and 16.1 ± 0.6 mg/g using RHS and Immobead S60S as supports, respectively, have been reached. The Sips isotherm model has been used which was well fitted to experimental data on TLL adsorption. Catalytic activities of immobilized TLL were assayed by olive oil emulsion hydrolysis and butyl stearate synthesis via an esterification reaction. Hydrolytic activity of the biocatalyst prepared with a commercial support (357.6 ± 11.2 U/g) was slightly higher than that of Gly-Epx-SiO2 prepared with RHS (307.4 ± 7.2 U/g). On the other hand, both biocatalysts presented similar activity (around 90% conversion within 9-10 h of reaction) and reusability after 6 consecutive cycles of butyl stearate synthesis in batch systems.