Improved immobilization of lipase from Thermomyces lanuginosus on a new chitosan-based heterofunctional support: Mixed ion exchange plus hydrophobic interactions

Abstract

In this study, a new mixed heterofunctional support (Chit-GA-Gly) has been prepared by sequential activation of chitosan hydrogel (Chit) with glutaraldehyde (GA) and further functionalization with glycine (Gly). The immobilization of the lipase from Thermomyces lanuginosus (TLL) on this support was compared with that on GA-activated Chit hydrogel (Chit-GA). The supports have been characterized by FT-IR, zeta potential and TG analyses. A similar maximum lipase loading of 53-55 mg per gram of support has been obtained for both supports. Both biocatalysts retained ≈40% of their initial activity after 48 h of incubation at 50 °C in heptane, toluene or iso-octane. The immobilization of TLL on Chit-GA proceeded via preferential covalent attachment (95%) and a combined ion exchange (cationic and anionic) and hydrophobic adsorption was observed using Chit-GA-Gly. TLL immobilized on Chit-GA-Gly was ≈4-times more active than when immobilized on Chit-GA in both olive oil emulsion hydrolysis and alkyl palmitate synthesis via esterification. Isoamyl palmitate synthesis in iso-octane at 50 °C using this new biocatalyst gave a maximum acid conversion of 85% after 90 min of reaction. After nine consecutive esterification batches, the biocatalyst retained around 40% of its initial activity.

Keywords: Catalytic properties; Chitosan-based hydrogels; Heterofunctional supports; Lipase.