Isolation And Identification Of Streptomyces Tumenensis Antagonistic To Curvularia Lunata And Studies On Fermentation Conditions Of The Strain

Eleven actinomycetes strains were isolated from different soil samples using dilution method Plate resist method combined with growth speed method was applied to select antagonists. After primary selection by plate resist method, 5 strains were acquired among which 3 strains behaved stronger inhibition activities. In the following selection, 1 strain named BPS2 showed the strongest inhibition activity. The fermentation filtrate showed a high inhibition activity against maize leaf spot caused by Curvularia lunata. Then, identification, optimum fermentation condition and antifungal test against Curvularia lunata were studied in this reportMorphological, physiological and biochemical tests and 16S rDNA sequence analysis were made to identify the strain BPS2. The results indicated that the 16S rDNA of BPS2 showed the highest homology to Streptomyces purpurascens with 97 % . But the morphological and physiological and biochemical character between them revealed distinctness. Based on the polyphase taxonomical views, BPS2 was identified as a new special of streptomyce and was denominated Streptomyces tumenensis BPS2. Its antifungal spectrum includes many plant pathogenic fungi such as Fusarium graminearum, Exserohilum turcicum, Cercosporidium sojinum, Cladosporium cucumerinum, Alternaria solani, Alternaria alternate, Alternaria alternate, Alternaria porri, Cercosporidium sojinum (Hara) , Fusarium solani. The fermentation filtrate showed a high inhibition activity against Gram-positive bacteria such as Staphylococcus aureaus, Bacillus subtilis; Gram-negative bacteria such as Escherichia coli, Mycobecterium tuberculosis.The optimum conditions were determined, which included sucrose 2.0 %, cornmeal powder 2.0 %, soybean powder 3.0 %, peptone 0.6 %, Ammonia sulfate 0.3 %, KH₂PO₄0 1 %, NaCl 0.1 %, CaCO₃ 0.3% in 1000 ml medium, the optimum initial pH was natural pH 6. Optimum fermentation condition of strain BPS2 was also determined, which indicated that antibiotics of strain BPS2 had strong inhibition activity with 28 h seed age, 6 % inoculation volume (v/v), the medium volume in the flask was 30 ml/250 ml, fermentation period was 60 hour, 200 r/min, 28℃fermentation temperature and pH was natural.Through control efficiency test, it indicated that the fermentation liquid of strain BPS2 had...