Primary Study Of The Antifungal Activity Of Bacillus Polymyxa JW-725

Bacillus polymyxa JW-725 isolated from the Tibet soil at an altitude of 4 671m by the researcher in our laboratory has the antifungal activity against the post-harvest plant pathogen Penicillicum italicum.The strain can grow on the carbon source glucose or soluble starch and the nitrogen source peptone or soybean powder, but not on the inorganic nitrogen source ammonium chloride or ammonium sulfate. The study shows that the strain cultured in the medium rich in carbon sources produces plenty of glutinous substances with low antifungal activity. On the contrary, the strain grows well in the medium rich in peptone and the supernatant shows a better antifungal activity.The fermentative liquid cultured at moderate and low temperature has no notable difference in the antifungal activity. But when the temperature is 50 ℃, the antifungal activity becomes weak. The initial pH of the medium affects the antifungal activity notably. When the pH is 3.0, the strain can not grow almost and the fermentative liquid shows no antifungal activity. However, the strain can grow in the pH9.0 mediurn and abetter antifungal activity is tested.Take the antifungal activity of the fermentative liquid as the target, the medium is the most important factor which has the effect on the antifungal activity. By the orthogonal experiment, the optimal fermentative condition of the strain is LB medium with initial pH9.0, 30℃, 72h, 10% inoculum and 100mL culture per 500mL shake flask.