Screen,identification and optimized fermentation condition of an actinomycete strain against pathogenic fungus Fulvia fulva

Abstract:

An actinomycete strain xjy was isolated from the soil of cotton field in Xinjiang against pathogenic fungus Fulvia fulva. The growth of 23 plant pathogens and 6 bacteria were strongly inhibitded by strain xjy on PDA plate. Antimicrobial spectrum of fermentation filtrate of strain xjy is extensive and selective to different pathogens. The morphology，cultural characteristics，physiological and biochemical properties，chemotaxonomy and 16S rDNA sequences of this strain were studied. The strain showed faint yellow vegetative mycelium，spiral spore-bearing filaments and column spores with smooth surface. No pigment was produced in culture. The cell wall typeⅠ and sugar type C showed the strain with streptomyces character. A phylogenetic tree was constructed by comparing with the published 16S rDNA sequences of the related species and showed 99.6% identity of nucleotide sequence of 16S rDNA with Streptomyces lavendulae. From the polyphasic taxonomical view，the strain xjy falls into Streptomyces lavendulae. The optimum fermentation condition of strain xjy for producing the most effective ferment filtrate were cultured in 2% soybean flour，2% glucose，0.8% NaCl，0.2% CaCO₃，0.32% (NH₄)₂SO₄，the initial pH of 7.0，at 28℃ and shaked at 180r/mim for 6d. These results are valuable to strain application，antibiotics purification and its industrialization.