GELLAN GUM

Description

Gellan gum is a kind of anionic polysaccharide produced through the submerged fermentation of the bacterium Sphingomonas elodea. It is soluble in water. It is a polymer with tetrascharide being the repeating unit; the tetrascharide consists of two residues of D-glucose and one of each residue of L-rhamnose and D-glucuronic acid. It can be used as a gelling, texturizing and suspension hydrocolloid. It is a suitable agar substitute which can be supplemented to various kinds of growth media for microbes, especially thermophilic microorganisms because of its resistance to relatively high temperature (120 degree). It can also be used as gelling agent in plant cell culture on Petri dishes. It can also be used as a food additive, e.g. it can be used in plant based milks to keep plant protein suspended in the milk.

Chemical properties

A high molecular weight polysaccharide gum produced by a pureculture fermentation of a carbohydrate with Pseudomonas elodea, and purified by recovery with isopropyl alcohol, dried, and milled. It is a heteropolysaccharide comprising a tetrasaccharide repeating unit of one rhamnose, one glucuronic acid, and two glucose units. The glucuronic acid is neutralized to mixed potassium, sodium, calcium, and magnesium salts. It may contain acyl (glyceryl and acetyl) groups as the O-glycosidically linked ester. It occurs as an off-white powder that is soluble in hot or cold deionized water.

The Uses of GELLAN GUM

Gellan Gum is an agar substitute and gelling agent, and useful in a wide variety of immobilization matricies.

The Uses of GELLAN GUM

gellan gum is used as a gelling agent, thickener, and stabilizer in cosmetic preparations.

The Uses of GELLAN GUM

Gellan Gum is a gum obtained by fermentation of the microorganism sphingomonas elodea. the constituent sugars are glucose, glucuronic acid, and rhamnose in the molecular ratio of 2:1:1, being linked together to give a primary structure consisting of a linear tetrasac- charine repeating unit. direct recovery yields the gum in its native or high acyl form in which two acyl substituents, acetate and glycerate, are present. gels from that form are elastic and cohesive. recovery after deacetylation has the acyl groups removed to yield the low acyl form; those gels are strong and brittle. in general, high acyl gellan gum dispersed in water swells to form a thick suspension and upon heating, it loses its viscosity upon hydration. low acyl gellan gum is only partially soluble in cold water and is dissolved by heating to 70°c or greater. gelation occurs upon cooling and reaction with ions, predominantly calcium ions. gellan gum is sensitive to ions. uses include bakery fruit fillings, confectioneries, icings, dairy prod- ucts, beverages, and coatings.

General Description

Typical working concentration: 1.5-2.5 g/L in plant tissue culture media; up to 10 g/L in microbiological media. Phytagel^? requires the presence of cations (especially divalent) for gelling to occur. Concentrations of calcium and magnesium contained in most plant tissue culture media are typically sufficient for gelation. Low-salt media formulations, especially those used in microbiological applications, may require supplementation with additional calcium or magnesium salts (e.g., CaCl₂ or MgSO₄) or higher concentrations of Phytagel.

Biochem/physiol Actions

Phytagel is intended for use in place of agar and other gelling agent for plant tissue culture. Phytagel has been shown to be a superior substitute for tissue-culture-grade agar in the micropropagation of banana plantlets.

References

https://en.wikipedia.org/wiki/Gellan_gum
http://www1.lsbu.ac.uk/water/gellan.html