Welan gum: microbial production, characterization, and applications.

Microbial exopolysaccharides are of high molecular weight, environment friendly valuable natural polymers, having applications in diverse areas such as food industry, pharmaceutical industry, cement systems and cosmetics industries. Welan gum, a microbial product holds an important place among the exopolysaccharides due to its novel properties and potential applications. The biopolymer welan gum is synthesized by the fermentation process mainly by the Alcaligenes sp., and is composed of polymer of tetrasaccharide backbone chain containing l-mannose, l-rhamnose, d-glucose, and d-glucuronic acid. It acts as a thickening, suspending, binding, emulsifying, stabilizing and viscosifying agent. It has important commercial applications in the cement systems. This review is primarily focused on the microbial production, purification, recovery, and the characterization based on the available published literature on the welan gum. Besides this, the biosynthesis and the various process factors affecting the production as well as properties of welan gum and its various applications have also been addressed.