Mutagenesis And Fermentation Conditions' Optimization Of An Endophytic Fungus Isolated From Vinca Minor Linn

The strain XM-J2 was an endophytic fungus previously separated from Vinca minor and could produce the bioactive compound vincamine like its host plant by HPLC detecting method. The work involved in this paper is focused on the mutagenesis study of the strain XM-J2, using different physical and chemic mutagens, in order to get mutant strain with higher vincamine yield.Both single-factor and multiple mutagenesises were used for mutagenizing the initial strain XM-J2 in the study. Through the UV, He-Ne laser and NaNO2 mutagenesises, the optimal single-factor mutagenic conditions were 100s,20min and 25min, respectively. Through two-cross mutagenesises of the UV, laser, NaNO2 and LiCl, the selected dominant strains were cultured simultaneously and compared according to their biomass and vincamine yield detected by both ultraviolet spectrophotometry and HPLC. The dominant high-yielding strain was then selected as XM-UL-7-5 by UV-laser mutagenesis. Its vincamine yield was increased from 0.563mg/L to 1.194mg/L and the biomass of the train was 6.41g/L, which was increased by 62.3% compared with the initial strain. The mycelial biomass of the train was 6.41g/L, which was increased by 62.3% compared with the initial strain. The relative experiments showed that the high-yielding trait of the strain inherited stably after successive subcultures.Additionally, the culture conditions were optimized in order to improve the production capability of the strain, y the solid culturing according to the growth rate and potentiality of the strain and the liquid culturing according to the comparative index of the strain biomass and vincamine yield, both the optimal solid and liquid culture were potato-sucrose medium. The initial experimental conditions of XM-UL-7-5 strain fermatation were as follows:the optimal carbon source, nitrogen source and temperature were glucose, peptone,28℃, respectively. The optimum culture medium selected by the orthogonal experiment of L16 (43) were potato-sucrose medium containing glucose 3%, peptone 2% and pH7.0, and on the basis of these conditions, both the dry weight of the strain and its product yield come up to the maxium as 9.4g/L and 1.653mg/L.