Levans are a group of fructans; polymers of fructose forming a non-structural carbohydrate, which in the case of levans can themselves link together to form super-molecules comprising even hundreds of thousands.
The shortest levan is 6-kestose, essentially a chain of three fructose molecules with a few extra atoms in one segment. Levans are produced in almost all bacterial versions of fructan production, as well as being possible to produce by fracturing soybean mucilage.