About Levan: Background
Levan is an unusual polysaccharide. It is made of fructose residues which are packed into a compact spherical structure. Unlike most polysaccharides, levan does not swell in water. Indeed the spheres are fairly stable withstanding 1 N HCl at 70°C for over an hour before depolymerization is complete.
There are two common fructans: Levan and inulin. These polymers of fructose are classified according to which carbon atoms are included in bonds between the fructose units. Levan is a polyfructose with largely β-2,6 bonds, while inulin has mostly β-2,1 linkages. Levan is more water soluble and has stronger adhesive properties than the β-2,1 linked polymer. Fructans produced by plants are generally of the inulin type and have a low molecular weight of a few thousand Daltons. High molecular weight levan is usually produced by fermentation of sugar. The size varies with the bacterial species, but is commonly several million Daltons. Our levan is produced by a species of Bacillus which has NOT been genetically modified.
Many microorganisms in natural environments produce extracellular polymeric substances (EPS). Levan is just one of the many EPS that have been identified. These extracellular materials are particularly abundant in fast flowing streams. They serve several functions including protection of the organism from desiccation and toxins. They may serve as a stored carbon source and anchor organisms in favorable habitats. As an exopolymer, levan is readily separated from the cellular debris during commercial production.