Xanthan gum is a
polysaccharide secreted by the
bacterium Xanthomonas campestris, used as a
food additive and
rheology modifier, commonly used as a food thickening agent (in salad dressings, for example) and a ster (in cosmetic products, for example, to prevent ingredients from separating). It is composed of pentasaccharide repeat units, comprising
glucose,
mannose, and
glucuronic acid in the
molar ratio 2:2:1. It is produced by the
fermentation of
glucose,
sucrose, or
lactose. After a
fermentation period, the
polysaccharide is
precipitated from a growth medium with
isopropyl alcohol, dried, and ground into a fine powder. Later, it is added to a liquid medium to form the gum.