Mutation Breeding And Fermentation Conditions' Optimizing Of An Endophytic Fungus Isolated From Gentiana Macrophylla Pall

QJ18 is an endophytic fungus isolated from the root of a rare medicinal plant Gentiana macrophylla Pall.The strain can produce gentiopicrin like its host.In order to improve the strain to get a high gentiopicrin producing variety,different physical and chemic mutagens were used to mutagenize the initial strain QJ18. Sixteen high-yield strains were obtained after mutagenized by UV,He-Ne laser, Nitrite,UV combined LiCl.The gentiopicrin yield of QJ18-UV-23,QJ18-J-34, QJ18-H-25,QJ18-UVL-32 were 1.252,1.170,1.091 and 1.287 times higher than that of the original strain,respectively.Moreover,the optimum mutagenic time is 80s, 60min and 30min,respectively.Both QJ18-UV-23 and QJ18-H-25 as second original strains were further mutagenized by He-Ne laser,eight high-yield strains were obtained.The gentiopicrin yield of QJ18-UVJ-7 and QJ18-HJ-16 were 1.362 and 1.232 times higher than that of original strain,respectively.By analyzing and comparing mutagenic effect of different mutagenic agent,it was found that the mutagenic effects of UV combined He-Ne laser was better than other mutagens the study used.According to the growth rate of colonies and their growth potential on different media,an optimum solid medium was selected.Through analyzing the amount of biomass and the yield of gentiopicrin,bean sprouts liquid medium was selected out; and then,by comparing different carbon source,nitrogen source,the optimum carbon and nitrogen source was selected,respectively.The suitable carbon and nitrogen source of both mycelial growth and gentiopicrin production are sucrose,urea and peptone.The fermentation conditions of QJ18-UVJ-7 were then further optimized by the orthogonal experiment of L16(4~4).The results showed that bean sprouts liquid medium as a basic culture medium,regulates the sucrose concentration to 50 g/L, peptonel.5 g/L,pH 6.0 and the temperature 28℃,were the optimum conditions for its mycelial growth;regulates the sucrose concentration to 50 g/L,peptone 1.5 g/L, pH 7.0 and the temperature 26℃were suitable for gentiopicrin production.