Identification Of Streptomyces Strain And Purification Of Its Active Metabolites For Biological Control On Take-all Of Wheat

Take-all, caused by the soilborne fungus Gaeumannomyces graminis var. tritici, is the most important root disease of wheat worldwide. A Streptomyces strain SCY114 which had potential of biological control on take-all was obstained from soil samples. A series of research on this Streptomyces strain were conducted, included taxonomy and fermentation conditions of strain SCY114, extraction process and structure assay of active component produced by SCY114. The results are as follows:1. Total 128 of Streptomyces strains were isolated from soli samples collected from Xuchang area. A strain SCY114, had effective and stable inhibitory action against Gaeumannomyces graminis var. tritici and extensive inhibition spectrum against other pathogens, was screened by dual culture and assay of fermented broth inhibitory to G. graminis var. tritici on PDA plates. Fermentation broth had tolerance to acid and alkali,temperature,ultraviolet, light. base on assay of physical and chemical properties of cultural filter from strain SCY114.2. Streptomyces strain SCY114 was classified and identified by using the methods of classical morphological, biochemical and molecular biological taxonomy. The result showed that strain SCY114 is belongs to Streptomyces scabiei. It is named after Streptomyces scabiei var xuchangensis.The study reported for the first time the antagonism of Streptomyces scabiei against Gaeumannomyces graminis.3. The optimization of the fermentation medium for strain SCY114 was defined as follows: soluble starch 2%, soybean meal 4%, magnesium sulfate 0.075%, dipotassium hydrogen phosphat 0.1%, ferrous sulfate·7 water 0.001%.The optimum conditions for fermentation in shake-flask were defined as follows:initial pH at 7.0;fermentation temperature,28℃; 48-hour old strains cultivated on medium for seed broth preparation;inoculation amount,6%;the volume of broth in a 250 mL flask,70 mL; rotational speed,200 r/min and fermentation time,5 days.4.Examinations of the changes in cell concentration,soluble sugar content,and pH in the metabolie process found that the antibiotic development and the hypha growth are the best in pH 8.1～8.3.Meanwhile ,the antibiotic derives from the basic substance involved in energy metabolism,but the antibiotic synthesis and using sugar have metrological relationship.5.By means of antibiotic special identification techniques including the paper chromatography in Doskochilova 8 menstruum system,Betina menstruum system and different pH menstruum system,active metabolites of strain SCY114 fermentation was indicated to be medium polarity,gender,water-insolubleⅠclass antibiotic.Active metabolites is pale yellow powder,which is soluble in dimethyl sulfoxide,chloroform and ethyl acetate.It is slightly soluble in petroleum ether,methanol and ethanol,but is insoluble in water.6.Active metabolites was obtained from the fermentation broth of SCY114 by pretreated of absolute ethyl alcohol,ethyl acetate extraction, silica gel column chromatography,silicon thin layer chromatography and Recycling preparative HPLC.By means of ultraviolet analysis,mass spectrum analysis,infrared spectral analysis and nuclear magnetic resonance map analysis,molecular weight of active metabolites is 466 and its molecular formula may be C27H27N6O 2.