Abstract
Bligh and Dyer (B & D) or Folch procedures for the extraction and separation of lipids from microorganisms and biological tissues using chloroform/methanol/water have been used tens of thousands of times and are “gold standards” for the analysis of extracted lipids. Based on the Conductor-like Screening MOdel for realistic Solvatation (COSMO-RS), we select ethanol and ethyl acetate as being potentially suitable for the substitution of methanol and chloroform. We confirm this by performing solid–liquid extraction of yeast (Yarrowia lipolytica IFP29) and subsequent liquid–liquid partition—the two steps of routine extraction. For this purpose, we consider similar points in the ternary phase diagrams of water/methanol/chloroform and water/ethanol/ethyl acetate, both in the monophasic mixtures and in the liquid–liquid miscibility gap. Based on high performance thin-layer chromatography (HPTLC) to obtain the distribution of lipids classes, and gas chromatography coupled with a flame ionisation detector (GC/FID) to obtain fatty acid profiles, this greener solvents pair is found to be almost as effective as the classic methanol–chloroform couple in terms of efficiency and selectivity of lipids and non-lipid material. Moreover, using these bio-sourced solvents as an alternative system is shown to be as effective as the classical system in terms of the yield of lipids extracted from microorganism tissues, independently of their apparent hydrophilicity.
Highlights
Lipids from microorganisms’ matrices such as microalgae or yeasts are hydrophobic molecules which are soluble in many organic solvents
They can be divided according to the polarity of their head groups: neutral lipids [1] which are synthetized by the cells to store energy, and polar lipids which are the matrix of the cellular membrane
The B & D method has been considered as the standard method for the determination of total lipids in biological tissues such as microorganisms
Summary
Lipids from microorganisms’ matrices such as microalgae or yeasts are hydrophobic molecules which are soluble in many organic solvents. They can be divided according to the polarity of their head groups: neutral lipids (acylglycerols, free fatty acids, sterols, sterols esters, waxes and hydrophobic pigments) [1] which are synthetized by the cells to store energy, and polar lipids (phospholipids, glycolipids, polysaccharides and proteins) which are the matrix of the cellular membrane. The initially extracted mixture of all biomolecules is separated into two phases: an organic-rich phase (OR) containing the total lipids and a water-rich phase (WR) containing others compounds (sugars, proteins, etc.)
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