Eutectic solvents with tuneable hydrophobicity: lipid dissolution and recovery.

Calvin Lo,Jeltzlin Semerel,Michel H M Eppink,Corjan Van Den Berg,René H Wijffels

doi:10.1039/d1ra00306b

Abstract

Despite the promising advantages of eutectic solvents, the application of these solvents as an extraction solvent is still limited due to the challenging product recovery. Previously, it was reported that lipids could be recovered from a hydrophobic eutectic solvent with the principle of switchable hydrophobicity. However, this method still involves additional chemicals, such as polymeric amines, water, and CO2, which need to be removed later. In this study, we proposed a different approach by shifting the hydrophobicity spectrum of a semi-hydrophobic solvent. Made of hydrophilic imidazole and hydrophobic hexanoic acid, this combination showed tuneable hydrophobicity when the composition was changed, shown by the change of dipolarity (π*) scale from solvatochromic analysis. At low imidazole content, the solvent was able to dissolve sunflower oil and algae oil, whereas, at high imidazole content, the solvent showed high affinity towards water. By adding imidazole to the solution of oil and the solvent, a phase split was induced between the oil-rich upper phase and the solvent-rich lower phase. With this approach, ∼75% of recovery efficiency was achieved for the two oils, with the purity of ∼100% for sunflower oil and 86% for algae oil.

Highlights

Eutectic solvents, including “deep eutectic solvents” (DES), have been gaining interest as alternative green solvents in the eld of extraction of natural compounds
Both hydrophilic and hydrophobic biomolecules can be extracted and separated.[18]. This approach involved two additional compounds which later need to be removed further downstream. We propose another approach to tune the hydrophobicity of a semi-hydrophobic solvent, consisting of 8142 | RSC Adv., 2021, 11, 8142–8149
The solubility of model oils was measured in the eutectic solvent with varying imidazole concentration

Summary

Introduction

Eutectic solvents, including “deep eutectic solvents” (DES), have been gaining interest as alternative green solvents in the eld of extraction of natural compounds. The properties of these solvents are claimed to be designable.[6,7,8] For example, if the mixture is made of bio-derived, safe, and biodegradable compounds, the solvent might be benign and sustainable.[5,9,10] These mixtures melt at lower temperatures than the parental constituents, such that allows the mixtures to be liquid at room temperature, even if the parental compounds are solids.[11,12,13,14,15] The depression of melting point can be found in “deep eutectic solvents”, and normal, ideal mixtures. Other strategies need to be developed to tackle this bottleneck in the near future

Methods

Results

Conclusion