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.

exopolysaccharides, biological activity, Structural characterization, endophytes, physiological role

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

[*]O[C@H]1[C@H](OC[C@H]2O[C@H]([*])[C@H](O)[C@@H](O)[C@@H]2O)O[C@@H]([C@H](O)CO)[C@@H]1O

324.282 g/mol (C₁₂H₂₀R₂O₁₀, R = next and previous repeats, not counted in mol weight)

The extracellular polysaccharide FO1 was isolated from the fermentation broth of an endophytic fungus (Fusarium oxysporum) of Ipomoea pes-caprae. Its structural characteristics were studied by chemical and methylation analyses, and 1D and 2D (1)H and (13)C NMR spectroscopy. Results indicated that this exopolysaccharide consists of a disaccharide repeating unit with the following structure (n approximately 111): [→2)-β-D-Galf(1→6)-α-D-Glcp(1→](n).

NMR spectroscopy, structure elucidation, extracellular polysaccharide, structural elucidation

13C NMR data:
Linkage	Residue	C1	C2	C3	C4	C5	C6
6	bDGalf	107.11	87.42	76.26	83.25	70.36	61.39
	aDGlcp	98.84	71.96	73.62	70.36	73.16	67.67


1H NMR data:
Linkage	Residue	H1	H2	H3	H4	H5	H6
6	bDGalf	5.03	4.03	4.10	3.88	3.85	3.63-3.77
	aDGlcp	4.93	3.43	3.57	3.29	3.61	3.51-3.72


1H/13C HSQC data:
Linkage	Residue	C1/H1	C2/H2	C3/H3	C4/H4	C5/H5	C6/H6
6	bDGalf	107.11/5.03	87.42/4.03	76.26/4.10	83.25/3.88	70.36/3.85	61.39/3.63-3.77
	aDGlcp	98.84/4.93	71.96/3.43	73.62/3.57	70.36/3.29	73.16/3.61	67.67/3.51-3.72

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

[*]O[C@H]1[C@H](OC[C@H]2O[C@H]([*])[C@H](O)[C@@H](O)[C@@H]2O)O[C@@H]([C@H](O)CO)[C@@H]1O

324.282 g/mol (C₁₂H₂₀R₂O₁₀, R = next and previous repeats, not counted in mol weight)