A strain Loq18 which possessea antifungal activity to several phytopathogenic fungi was isolated from the soil in farmland. The strain was identified to be Bacillus subtillis.The crude antifungal protein was obtained by ammonium sulfate precipitation from Sterilizrtion broth. In order to determine the physical and chemical properties of the antifungal substances produced by Bacillus subtilis strain Loq18 , the effects of tempersture. pH values, ultraviolet. organic solvents. and protease were atudied. The results ahowed that this crude antifungal substannces were thermal stable. about 98 ％ of the initial activity remained after heating at 121 ℃ far 20 min; they were not sensitive to acidity-alkalinity . in the pH range of 4 - 11 were stable ; the antifungal activity was almost not be destroyed when they were under UV irradiation for10 h; when they were treated by ether and scetone, their inhibition activity remained above 90 ％ of control; they were not sensitive to proteane.%从农田土壤中分离得到1株对多种植物病原真菌有拮抗作用的菌株Loq18,经生理生化及分子鉴定确定为一株枯草芽孢杆菌,其无菌发酵液经硫酸铵沉淀得抗菌粗蛋白.为明确此抗菌粗蛋白的理化性质,研究了温度、pH变化、UV照射、有机溶剂和蛋白酶对抗菌蛋白稳定性的影响.结果表明,该抗菌粗蛋白具有良好的热稳定性,121℃高压灭菌处理20min后仍具有对照活性的95%以上;对酸碱不敏感,在pH值4～11范围内相对稳定;对紫外线穗定,在紫外光下照射10h以上时,其活性基本不受影响;经乙醚、丙酮等有机溶剂处理后仍具有对照活性的90%以上;对蛋白酶较稳定.
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