Screening Of Saponin-Producing Endophytes And Optimization Of Fermentation Condition

According to related reported studies,endophyte can produce the same active ingredients as host plantation and promote syntheses of secondary metabolites from host plantation by various enzymes.As we all know,ginseng is traditional Chinese medicine,of which the main active ingredient is ginsenoside,a triterpene compound.There are two main biosynthetic pathways for triterpene compound:MVA and MEP,among which MVA starts from Acetyl-CoA and undergoes a series of enzymes,while MEP starts from pyruvic acid.In this study,the endophytic bacteria that could produce rare ginsenosides were isolated from Panax species plants.The optimal medium and nutrition factors such as carbon source,nitrogen source and inorganic salt were selected and the secondary metabolites were separated and analyzed.The influence on the biosynthesis of rare ginsenosides by sodium acetate,sodium pyruvate,glycerol,salicylic acid,silver nitrate and some other inducing agents was discussed.192 species of endophytes were isolated from Panax ginseng.Among these strains,25 kinds of strains of high-yield ?-glycosidase microorganisms were isolated.From which,we also found that 13 kinds of strains could produce ginsenosides.The strain 17-15 can produce rare ginsenoside F2.The optimized fermentation condition for strain 17-15 was obtained by optimizing the ferment conditions of endophytes(including culture medium,pH,fermentation time,etc).The most suitable conditions are as follows:culture medium:PDA;pH7.0;fermentation time:7days.Under the three conditions above,conduct multi-factors experiments on strain PD 17-15.Analyze PD17-15 by TLC and HPLC and the optimal added dosages are as below:30mg of sodium pyruvate,30mg of sodium acetate,2mmol of glycerol,1Omg of salicylic acid,10mg of silver nitrate.Besides,fermentation products contain rare ginsenoside F2,Rg3,protopanaxadiol PPD and protopanaxtriol PPT.At last,identify endophyte on its productivity of saponin by combining morphological observation and molecular biological identification.The results indicate that endophyte strain PD 17-15 belongs to Bacillus aerophilus.