Dual role of a natural deep eutectic solvent as lipase extractant and transesterification enhancer

Abstract

The present work demonstrates the suitability of a natural deep eutectic solvent (DES) composed of glucose and cholinium chloride to act both as lipase extractant and biodiesel enhancer. After having demonstrated the viability of using this DES as segregation agent in aqueous solutions of non-ionic surfactants widely employed as lipase inducers in culture media (Tween 20 and Tween 80), the immiscibility gaps where characterized by ascertaining the binodal curves and tie-lines at several temperatures. Then, the effect of phase forming components concentration on Candida antarctica lipase B (CALB) extraction was investigated, concluding that a careful selection of feed composition allows reaching almost 100% of CALB extraction to the DES-rich phase. Additionally, the role of DES as coadjuvant in CALB-catalyzed glycerol-free transesterification was evaluated after an initial optimization of the reaction conditions (enzyme load and DMC:oil molar ratio). It was concluded that the use of the proposed natural DES led to biodiesel conversions 3 times higher than the levels attained with a conventional imidazolium-based ionic liquid (C2C1imC2SO4), or 20% higher than control transesterification reactions (without coadjuvant).