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[Objective] The paper was to improve the antimicrobial effect of antagonistic Streptomyces on Botryosphaeria dothidea. [Method]Different concentrations of DES were adopted for mutagenic treatment of antagonistic Streptomyces F-58. After fermentation,the mutant strain numbered F-58-06 with genetic stability and good antimicrobial effect was selected among 200 mutant strains; the biological activity of the strain was determined with B. dothidea as the indicator fungus,and the best concentration of DES was 2%. The fermentation conditions of antagonistic substances of Streptomyces strain F-58-06 produced in shake flasks were optimized using the method of single factor and orthogonal experimental design. [Result] The optimal fermentation conditions were carbon source corn flour,nitrogen source KNO_3,initial p H 7,loading volume 30 m L in 250 m L shake flask,inoculation volume 3%,incubation time 132 h. Based on orthogonal experiments,the best cultured medium ratio was corn flour 4%,KNO_30. 5%,Ca CO_30. 2%,Na Cl 0. 35%,Mg SO_4·7H_2O 0. 15%. [Conclusion]After mutation and optimization of culture medium,the antimicrobial activity of Streptomyces F-58 was greatly improved,and the average inhibition zone diameter was 1. 35 times of that of the original strain.
[Objective] The paper was to improve the antimicrobial effect of antagonistic Streptomyces on Botryosphaeria dothidea. [Method] Different concentrations of DES were taken for mutagenic treatment of antagonistic Streptomyces F-58. After fermentation, the mutant strain numbered F-58-06 with genetic stability and good antimicrobial effect was selected among 200 mutant strains; the biological activity of the strain was determined with B. dothidea as the indicator fungus, and the best concentration of DES was 2%. The fermentation conditions of antagonistic substances of Streptomyces strain F -58-06 produced in shake flasks were optimized using the method of single factor and orthogonal experimental design. [Result] The optimal fermentation conditions were carbon source corn flour, nitrogen source KNO 3, initial pH 7, loading volume 30 m L in 250 mL shake flask, inoculation volume 3%, incubation time 132 h. Based on orthogonal experiments, the best cultured medium ratio was corn flour 4%, KNO_30.5 %, CaCO_30.2%, NaCl 0.35%, MgSO_4.7H_2O 0.15%. After mutation and optimization of culture medium, the antimicrobial activity of Streptomyces F-58 was greatly improved, and the average inhibition zone diameter was 1. 35 times of that of the original strain.