Screening And Identifying Of Antagonistic Actinomyce Against Cladosporium Fulvum Cooke And Optimizing Of Fermentation Condition Of The Antibiotic

Eleven actinomycetes strains were isolated from different soil samples using dilution method. Plate resist method combined with growth speed method were applied to screen antagonists.After primary selection by plate resist method, 7 strains were acquired,among which 3 strains behaved stronger inhibition activities. In the following screen,1 strain named BPS2 showed the strongest inhibition activity with inhibition zone of 15.5mm.The fermentation liquid showed a high inhibition activity against Gram-positive bacteria such as Staphylococcus aureaus, Bacillus subtilis;Gram-ne- gative bacteria such as Escherichia coli,Mycobecterium tuberculosis and many kinds of plant pathogenic fungi such as Fusarium graminearum, Curvularia lunata, et al besides Cladosporium fulvum cooke.It.s morphological, cultural physiological, biochemical characteristics, chemotaxonomy and 16SrDNA sequences analysis were studied.The substrate mycelium have no partition, the aerial mycelium are ramose; the spores are oval and the surface are smooth. Cell wall typeⅠ, Sugar type E were consistent with the characteristics of the genus Streptomyces. The phylogenetic tree analysis from almost complete 16SrDNA showed that the strain BPS2 was very similar with 23 model Streptomyces for 95.2%-97% identity. The 16SrDNA sequence data confirmed the generic assighment. In the phylogenetic tree strain BPS2 was most closely related to S. purpurascens DSM 40310T, sharing 16SrDNA similarity value of 97%. However, the morphological and physiological characteristic between BPS2 and S. purpurascens revealed obvious difference. Based on the polyphase taxonomical data, BPS2 was identified as a new strain of streptomyces and was denominated as Streptomyces tumenensis BPS2.The fermentation conditions were determined through quadrate experiment. The optimum combination of medium was Sucrose 1.0 %, Cornmeal 2.0 %, Peptone 0.3 %, Soybean powder 3.0%, Ammonia sulfate 0.5 %, MgSO4 0.1 %, NaCl 0.2 %, KH2PO4 0.02 %, CaCO3 0.3 %, FeSO4 0.01%; the optimum fermentation parameters were as follows: culture temperature (28℃), initial pH (6.0), seed age (22 hrs), inoculation volume (6 %), 70ml liquid medium in 250ml flake, 180 r/min for 60hrs.Through germination test and bio-control efficiency test in green-house, it indicated that the fermentation liquid of BPS2 could improve the tomato seed germination rate, promote its growth and had better bio-control efficiency against Cladosporium fulvum cooke under...