Recent advances in endophytic exopolysaccharides: Production, structural characterization, physiological role and biological activity.

Endophytes are microorganisms that colonize living, internal tissues of plants without causing any immediate, overt negative effects. In recent years, both endophytic bacteria and fungi have been demonstrated to be excellent exopolysaccharides (EPS) producers. This review focuses on the recent advances in EPS produced by endophytes, including its production, isolation and purification, structural characterization, physiological role and biological activity. In general, EPS production is influenced by media components and cultivation conditions. The structures of purified EPS range from linear homopolysaccharides to highly branched heteropolysaccharides. These structurally novel EPS not only play important roles in plant-endophyte interactions; but also exhibit several biological functions, such as antioxidant, antitumor, anti-inflammatory, anti-allergic and prebiotic activities. In order to utilize endophytic EPS on an industrial scale, both yield and productivity enhancement strategies are required at several levels. Besides, the exact mechanisms on the physiological roles and biological functions of EPS should be elucidated in future.