The development of a capillary microreactor for transesterification reactions using lipase immobilized onto a silica monolith

The use of lipase immobilized on a silica monolith as a microreactor for performing lipid transformations is reported. The microreactor consists of a monolithic network formed within a 320 μm internal diameter fused silica capillary that provides a very large surface area for enzyme immobilization. Candida antarctica lipase was covalently bound onto the silica monolith using glutaraldehyde as the cross linking reagent. Successful immobilization was demonstrated by FTIR measurements on monolith fragments. The effectiveness of flow-through microreactors was tested for the ethanolysis of triolein (TO) at room temperature. TO was quantitatively transformed into ethyl oleate when using flow rates of < 1 μL/min. Non-aqueous reversed phased-high performance liquid chromatography (NARP-HPLC) with an evaporative light scattering detector (ELSD) and gas chromatography/mass spectrometry with electron impact ionization (GC/MS-EI) were both used for characterization and quantification of the products. The microreactors were used to perform lipid transformations directly online with atmospheric pressure photoionization (APPI) ionization mass spectrometry. They were also shown to be reusable without loss of activity for ~15 runs when operated at room temperature and flow rates of < 1 μL/min.