Immobilization of Chromobacterium viscosum lipase on Eudragit S-100: coupling, characterization and kinetic application in organic and biphasic media

The application of Eudragit S-100 for the immobilization of a commercial lipase from Chromobacterium viscosum was studied. The enzyme immobilization by a covalent method (carbodiimide method) was assayed. However, it was observed that immobilization occurred preferentially by adsorption. The strength of lipase adsorption to Eudragit was evaluated under different conditions, namely those used for precipitation of polymer conjugates. In order to hamper the adsorption process, different experimental conditions were tested, namely the use of 0.1–1.0% (v/v) Triton X-100 and high salt concentrations (0.2–0.5 M NaCl). It was observed that NaCl does not prevent the adsorption except when combined with the detergent. Around 60% of the lipase remained in the supernatant in the presence of 0.5 M NaCl and 1% (v/v) Triton X-100, after 3 h of incubation. In these conditions and in the presence of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC), 20% of pure lipase was covalently bound to Eudragit S-100 after 24 h of incubation. The C. viscosum lipase–Eudragit S-100 conjugate was further used to study the esterification reaction of different alcohols and fatty acids, in organic medium, at 37 °C. The maximum activity (18.9 U/mg) was obtained for the synthesis of hexyl oleate. A similar activity was obtained in a biphasic system (18.3 U/mg) using isooctane as organic phase. The optimal temperature for the esterification reaction was 65 °C, at pH 7.0 High activities were also observed for temperatures between 70 and 80 °C in a biphasic system.