The Diversity Of Ginseng Rhizosphere Soil Fungi And Endophytes And Screening Of Ginsenoside Biotransformating Strains

Ginseng (Panax ginseng C.A.Meyer ) as a member of Araliaceae is one kind of perennial herbaceous plant, it is a traditional herb in China. It ranked the top medicine in"Shen Nong's Herbal Classic"because of its numerous functions, such as supplying strength, keeping calm and so on. As a common nourishing and strong medicine, it is used widely by more and more people in recent years. During the growing seasons of ginseng in field, large amounts of microorganisms grow in its rhizosphere soil or inside of roots due to its specific chemical compounds. It has been realized that some of these microorganisms are contributive to the formation of specific secondary metabolites or function as enzymatic catalysis.The paper deals with the diversity of fungi in rhizosphere soil of ginseng and endophyte in ginseng plant by methods of fungal isolation, purification and identification of soil fungi and endophytes. It is designed to imply the main fungal species in ginseng soil and their distribution characteristics, and to screen for economically invaluable fungal species. Meanwhile these fungal speices were investigated for biotransformation of ginsenosides, which are the main active substances in medicins.During July and October in 2009, samples of ginseng roots and rhizosphere soil were collected in ginseng-growing areas of Liaoning and Jilin Provinces. A total of 105 fungal strains were isolated and cultured, including strains IBE023001-105. Morphologically 48 fungal species belonging to 15 genera were identified. Some fungal strains were important pathogens of medicinal plants, such as Cylindrocarpon didymium, Cylindrocarpon destructans, Fusarium oxysporum and F. solani and so on. Of which Zygorhynchus moelleri and Absidia glauca were important fungal endophytes.The 105 fungal strains were investigated for microbiological transformation of ginsenoside Rb₁,Rb₂,Rc,Rd and Rg₁. The TLC analysis primarily indicatesd that 24 strains were founded to have transformation function. After HPLC analysis, five fungal strains were found to convert ginsenoside Rb1 to Rd, four strains to convert ginsenoside Rb1 to Rg₃, five strains to convert ginsenoside Rb1 to Rh₂, four strains to convert ginsenoside Rd to Rg₃ and Rh₂. Among these strains Zygorhynchus moelleri (IBE023087) and Absidia glauca (IBE023105) were found to have the specificity to transform ginsenoside Rb1 to ginsenoside Rd and have shown to possess commercial potential for production of ginsenoside Rd.