Gellan

Gellan gum is an anionic extracellular bacterial polysaccharide identified in 1978 by CP Kelco (San Diego, USA). It is available in two forms in normal commercial production, native gellan gum and deacylated gellan gum. For deacylated gellan gum, acyl groups present in the native polymer are removed by alkaline hydrolysis resulting deacylated polymer which is known generically as “gellan gum.” Gellan gum can form gels at low concentrations when hot solutions are cooled in the presence of gel promoting cations which provides it as a texture modifier to control the viscoelasticity in foods, as delivery vehicle in pharmaceuticals, and as cell encapsulation material in tissue engineering etc. Gellan gum has been extensively used as a culture medium in microbiology, as a rheology modifier in foods and cosmetics industries since the early stage of its discovery. Recently, gellan gum as a natural polymer and its hydrogel show a wide range of application perspective in drug delivery and tissue engineering. Gellan gum is nontoxic, biocompatible, biodegradable and the resulting hydrogel is transparent and stable. However, gellan gum-based hydrogels have intrinsic defects such as lack of toughness and tissue tolerance as tissue engineering materials that restrict their use in biomedicine field. In order to solve these problems, quite a large number of studies on chemical modification of gellan gum have been carried out. In this chapter, the gelation behaviors, mechanism as well as various modification methods of gellan gum are summarized. Applications of gellan gum and modified gellan gum in food and biomedicine are highlighted.