Xanthan Gum is a plant-based thickening and stabilizing agent. It is named for the bacteria, Xanthomonas campestris, which plays a crucial role in this description. Technically speaking, xanthan gum is a polysaccharide, which is just a fancy way to say "a string of multiple sugars." To create xanthan gum, the Xanthomonas campestris bacterium is allowed to ferment on a sugar. The result is a gel that is then dried and milled to create the powder substance.