- Gellan gum is a high-molecular-weight polysaccharide produced by the bacterium Sphingomonas elodea through fermentation.
- Chemically, it is a linear anionic heteropolysaccharide composed of repeating tetrasaccharide units: glucose, glucuronic acid, and rhamnose in the sequence [→3)-β-D-Glc-(1→4)-β-D-GlcA-(1→4)-β-D-Glc-(1→4)-α-L-Rha-(1→]. Depending on the production and purification process, gellan gum can exist in two primary forms: high-acyl and low-acyl. High-acyl gellan contains acetyl and glyceryl substituents, which provide elasticity and flexibility to gels, while low-acyl gellan lacks these groups and forms firm, brittle gels.
- One of the defining characteristics of gellan gum is its gel-forming ability. When dissolved in hot water and subsequently cooled in the presence of cations such as calcium, magnesium, or potassium, gellan molecules align into double helices that aggregate into a three-dimensional network, creating strong, transparent gels. This gelling mechanism gives gellan gum remarkable thermal stability and allows precise control over gel texture by adjusting cation concentration, pH, or the ratio of high- and low-acyl forms. Because of this versatility, it has become a widely used hydrocolloid in the food, pharmaceutical, and biotechnology industries.
- In the food industry, gellan gum is employed as a stabilizer, thickener, and gelling agent. It provides clarity and suspension stability in beverages, enabling insoluble particles like vitamins, minerals, or fruit pulp to remain evenly distributed. It is also used to create structured desserts, confectionery gels, plant-based dairy alternatives, and low-calorie foods, thanks to its ability to form gels at very low concentrations (as little as 0.05–0.3%). Unlike many other gums, gellan gels can withstand a wide range of pH and temperature conditions, which broadens their applicability in food processing.
- Beyond foods, gellan gum plays an important role in pharmaceuticals and medicine. It is valued for its biocompatibility and biodegradability, making it a candidate for drug delivery systems, tissue engineering scaffolds, and wound dressings. Ophthalmic formulations often use gellan gum in in-situ gelling eye drops, where the solution transforms into a gel upon contact with the ions in tear fluid, prolonging drug residence time on the eye surface. In biotechnology, gellan gum is also used as a microbial culture medium alternative to agar, offering superior clarity and reproducibility.
- From an industrial perspective, gellan gum has advantages in eco-friendly materials and specialty applications. Its gelation properties are being investigated for controlled-release fertilizers, cosmetic formulations, and biodegradable coatings. Because it can be produced efficiently through microbial fermentation, it provides a renewable and consistent source of hydrocolloid compared to plant-derived gums, which may vary with season or geography.
