Xanthan Gum - Ingredipedia, the Ingredient Encyclopedia

Xanthan gum (or xanthum gum) is a natural gum polysaccharide used as a food additive and rheology modifier. It is produced by a biotechnological process involving fermentation of glucose or sucrose by the Xanthomonas campestris bacterium.

http://en.wikipedia.org/wiki/Xanthan_gum