Gellan gum is a water-soluble polysaccharide produced by Pseudomonas elodea, a bacterium.
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The repeating unit of the polymer is a tetrasaccharide, which consists of two residues of D-glucose and one of each residues of L-rhamnose and D-glucuronic acid. The tetrasacharide repeat has the following structure:
[D-Glc(β1→4)D-GlcA(β1→4)D-Glc(β1→4)L-Rha(α1→3)]n. As it is evident from the formula, the tetrasacharide units are connected by (α1→3) glycosidic bonds.
Gellan gum, also branded by few suppliers as AppliedGel, Phytagel or Gelrite, is used primarily as a gelling agent, alternative to agar, in microbiological culture. It is able to withstand 120 °C heat, making it especially useful in culturing thermophilic organisms. One needs only approximately half the amount of gellan gum as agar to reach an equivalent gel strength, though the exact texture and quality depends on the concentration of divalent cations present. Gellan gum is used as gelling agent in plant cell culture on Petri dishes, as it provides a very clear gel, facilitating light microscopical analyses of the cells and tissues. Although advertised as being inert, experiments with the moss Physcomitrella patens have shown that choice of the gelling agent - agar or Gelrite - does influence phytohormone sensitivity of the plant cell culture.[1]
As a food additive, gellan gum is used as a thickener, emulsifier, and stabilizer. It has E number E418. It was an integral part of the now defunct Orbitz soft drink.
It is used in soya milks to keep the soy protein suspended in the milk.[2]