Sustainable aqueous biphasic system created using sugar-based deep eutectic solvents/ethyl lactate for the green extraction of biomolecules

Abstract

In recent years, the use of green solvents with efficient extraction techniques has gained considerable interest in the research community. This study proposed a novel aqueous biphasic system (ABS) consisting of a hydrophilic sugar-based deep eutectic solvent (DES) and biodegradable ethyl lactate (EL). To understand the phase behaviour of sugar-based DES-EL ABS, at 298.15 K and at an atmospheric pressure, the phase diagrams were determined, and the effects of the structure of different saccharides such as HBDs on the phase separation were discussed. By fitting the effective excluded volume theory (EEV) model to phase diagram data, the ability of the monosaccharide/disaccharide-based DES to induce phase separation was determined. Furthermore, the tie-line length (TLL) was measured and analysed for the stability of DES in both phases at equilibrium. Finally, extraction experiments of such systems for five target biomolecules (eugenol, vanillin, vanillic acid, gallic acid and rutin) were conducted. The results indicated that the hydrophilic/hydrophobic nature of biomolecules preferentially drives their partitioning behaviour. Eugenol, vanillin, and vanillic acid preferentially migrated to the more hydrophobic EL-rich phase, whereas gallic acid and rutin entered the hydrophilic DES-rich phase. A combination of factors such as pH, viscosity and TLL of the system can also affect the separation efficiency. The results of the extraction experiments confirmed the good feasibility of the proposed system for biomolecular extraction applications.