Glycolipid

What is a glycolipid?

A glycolipid is any molecule in which a carbohydrate is attached to a lipid. The term covers a large family. In biology, glycolipids are components of cell membranes in plants, animals and microorganisms, where the sugar portion often faces the outside of the cell. In industrial chemistry, the term most often refers to the glycolipids that microorganisms release into their surroundings, which act as biosurfactants.

Why glycolipids are surface-active

The two halves of a glycolipid behave very differently in water. The sugar group carries several hydroxyl groups and is attracted to water. The fatty acid chain is a hydrocarbon and is repelled by water. A molecule built that way is amphiphilic, the same basic architecture as a synthetic surfactant, so glycolipids collect at interfaces, lower surface tension and interfacial tension, and form micelles above their critical micelle concentration.

Because the head group is a sugar rather than a charged group such as a sulfate, many glycolipids behave largely like nonionic surfactants, although some carry an acid group that can be charged depending on pH.

Main types of glycolipid biosurfactants

Glycolipid	Sugar group	Typical producing organisms
Sophorolipids	Sophorose (two glucose units)	The yeast Starmerella bombicola
Rhamnolipids	One or two rhamnose units	Pseudomonas bacteria
Mannosylerythritol lipids	Mannose joined to erythritol	Yeasts formerly classed as Pseudozyma
Trehalolipids	Trehalose	Rhodococcus and related bacteria

Within each type, the producing organism makes a mixture of closely related molecules that differ in fatty acid chain length, in the degree of acetylation of the sugar, or in whether the molecule is closed into a ring. Those variations change solubility, foaming and how strongly the molecule lowers interfacial tension, so the strain and fermentation conditions shape the properties of the final product.

How glycolipids are made

Glycolipid biosurfactants are produced by fermentation. The organism is grown on a carbon source such as sugar, plant oil or both, and produces the glycolipid as part of its metabolism, often releasing it into the broth. The product is then recovered and purified. Yields, and the proportions of the different molecular forms, depend on the strain, the feedstock and the process conditions, which is where approaches such as precision fermentation focus.

Where glycolipids are used

Glycolipid biosurfactants are used as co-surfactants and wetting agents in cleaning products, as components of agricultural adjuvants, in oilfield treatments, in mineral processing, and in personal care. They are generally reported as readily biodegradable, which is one reason for their use as replacements for petrochemical surfactants, though biodegradability should be confirmed for each specific product with a standard test such as OECD 301.

Glycolipids at Locus

Locus describes its products as glycolipid biosurfactants. Its Amphi ingredient line is sold to formulators as a glycolipid co-surfactant, and its oilfield and mining products are built on the same platform.

Frequently asked questions