Optimization Of Fermentation Conditions Of Bacillus Atrophaeus XW2

Bacillus atrophaeus XW2 is a beneficial antagonistic strain isolated from the healthy leaves of poplar tree in the laboratory.The strain has a broad spectrum of inhibition and a strong inhibitory effect on a variety of pathogenic fungi.It is a strain that have a broad application prospects.Based on the previous studies,the basic fermentation medium of Bacillus atrophaeus XW2 was screened.The fermentation medium and the fermentation conditions of the strain XW2 were optimized to obtain the optimum fermentation medium formulation and fermentation conditions,and then we use the liquid fermentation tank of 10 L to expand and culture strains,and growth curve of the strain was drawn and the optimal time for tank release was determined at last.Finally,a biocontrol agent of Bacillus atrophaeus XW2 was initially developed.The bacteriostasis activity of 4 pathogenic bacteria of Fusarium graminearum,Cytospora ambiens,Absidia sp.and Colletotrichum populi were detected by mycelium growth rate method.The bacteriostasis activity of the bacteriostat was detected which provided a vital basis for the large-scale commercial production and application of Bacillus atrophaeus XW2 bacteriostat.The final results were as follows:(1)The optimum fermentation medium was selected:carbon source for]5 g of bran,the nitrogen source was soy peptone 5 g,manganese sulfate 0.1 g,calcium carbonate 3 g,distilled water 1L,pH 7.0.(2)The optimum fermentation conditions:Initial pH 6.5,100 mL/250 mL Erlenmeyer flask,with 3%inoculum,optimal viable biomass at a shaker speed of 200 rpm and temperature of 30?.(3)The strain was expanded and cultured by using 10 L fermentor.The optimal time for the release of the fermentor was 27 h,the live bacteria amount reached 1.33 × 109 cfu/mL.(4)XW2 bacteriostat was prepared by adsorption with calcium carbonate carrier.The XW2 bacteriostat was tested to affect the growth process of the 4 pathogens,and the bacteriostatic activity was strong,and their EC50 values were 4.74 mg/mL,3.33 mg/mL,4.01 mg/mL,3.32 mg/mL,respectively.