Abstract: The aim of this research was to obtain the optimal fermentation conditions of Streptomyces rectiviolaceus A8, and to preliminarily determine its metabolic bioactive substances and control effect of rice sheath blight. The fermentation conditions were optimized by carbon and nitrogen single factor experiment and orthogonal experiment. The active substances produced by strain A8 were preliminarily detected by gas chromatography-mass spectrometry (GC-MS). Taken Rhizoctonia solani and Baccillus cereus as target bacteria, activities of the identified components were determined, and the control effect of strain A8 on rice sheath blight was investigated in the field test. The results showed that the optimal formula for strain A8 was starch soluble 3%, soybean mealy 0.6%, east extract 0.4%, NaCl 0.05%,K₂HPO₄·3H₂O 0.05%,MgSO₄·7H₂O 0.05% and FeSO₄·7H₂O 0.001% The optimal fermentation conditions was loaded liquid 100-200 mL/500 mL, inoculation amount 3%-7%, fermentation temperature 28℃~31℃and initial pH value 7.0~8.0. Twenty-six compounds were separated and identified from the crude extract. The biological activity test showed that the bacteriostasis rate of 3-methyl-1,2-cyclopentanedione, 1,2,4,5-tetramethyl-benzene and dihydro-3-methylene-2,5-furandione against Rhizoctonia solani was over 70%, and dihydro-3-methylene-2,5-furandione, 2-furancarboxylic acid, hydrazide, catechol and 3-methyl-1,2-cyclopentanedione had strong antibacterial effect on Bacillus cereus. The actinomycete has the potential to simultaneously inhibit fungi and bacteria, and provides good materials for the development of broad-spectrum biocontrol preparations. Field trials demonstrated that strain A8 had control effect on rice sheath blight, equal to that of Bacillus subtilis BT205.

Key words: Streptomyces rectiviolaceus A8, fermentation condition, metabolizes bioactive substance, gas chromatography-mass spectrometry, rice sheath blight