Identification of an endophytic fungus Pilidiella guizhouensis isolated from Eupatorium chinense L. and its extracellular polysaccharide

An endophytic fungus strain ZJSRU-M1 was isolated from Eupatorium chinense L. The phylogenetic tree analysis indicated that the ITS sequence of ZJSRU-M1 was similar to that of Pilidiella guizhouensis. Therefore, the endophytic fungus was identified as Pilidiella guizhouensis. The strain could produce a lot of exopolysaccharides in the process of liquid fermentation. The exopolysaccharide from the submerged culture of P. guizhouensis ZJSRU-M1 (PGP) was purified. Its molecular weight was determined by HPGPC with the average molecular weight of 13.4 kDa. The monosaccharide composition of PGP was determined by GC–MS, indicated that it was a homogeneous polysaccharide, consisted of glucose only. And PGP was detected by FT-IR spectroscopy and UV spectroscopy, suggested that it was a polysaccharide structure. In addition, the antioxidant activity of PGP in vitro, including scavenging ability on DPPH radical, hydroxyl radical and superoxide anion, suggested that PGP had strong antioxidant activity. These findings suggested that exopolysaccharide from endophytic fungus P. guizhouensis had the potential application for the development of antioxidant drugs or health products.