Preliminary Study On Characteristic And Production Condition Of Antifungus Substance From Bacillus Subtilis Strain B68

Bacillus subtilis strain B68 has a strong antagonism to the pathogen of banana and other crops in tropic area, so it is very import to exploit biopesticide by this strain. In this study, the resistance spectum,separation and purification of antibacterial substance,fermentation conditions for production of antibacterial substance and characteristics of antifungal substance were tested respectively. The results of this study as the following:1. The bioassay result revealed that Bacillus subtilis strain B68, and its germfree filtrate and purification had strongly antagonism activity against 9 pathotypes that were screened from banana fruit; it is showed extensively inhibitory activities against pathogen of banana.2. The germfree filtrate and purification of Bacillus subtilis strain B68 also showed distinct antagonistic activities to the standard pathogen Fusarium semitectum 4. After cultured, more and more of the deformed cell and larger and larger of dilate cell with the increase of culture time, so that the hyphas seem form some strings of beads. Then deformed spherical cells separated each other and hyphas broke in many small segments, the cytoplasm oozed out of the cells so as to most of cells become to empty.3. The inhibit activities to pathogen conidia were presented by the germfree filtrate and purification even diluted by 400 times, and the spores were stopped germinate even after diluted by 40 times.4. The ferment filtrate and purification substance were unthermostable, for its antifungal activity was decreased after being sterilized at 121℃for 20 min.5. A majority of activity substance was kept in the water after extraction by Ethyl acetate,chloroform,benzine,normal butyl alcohol。while can melt in methyl alcohol,absolute ethyl alcohol,isopropyl alcohol,econdgrade nitrile,ormaldehyde,acetone and keep its activities.6. The substance still show antifungal activities after prettification by 20%-80% (NH₄)₂SO₄, while the abilities was lost if the concentration of (NH₄)₂SO₄ more then 80%. 7. The fermentation conditions of Bacillus subtilis strain B68 was medium of SDY, pH7.0, the temperature must be controlled in 28℃and rate speed was 140r/min. After 96 hours, the high quality and quantity of activities were obtained from ferment filtrate by extraction of (NH4)2SO4.8. An antagonistic substance purified by ammonium sulphate, and its ninhydrin reaction and biuret reaction were positive after acid hydrolysis. Above mentioned results indicated that the main activity in the filtrate of Bacillus subtilis strain B68 was protein with cycpeptide.