Preliminary Studies On Purification And Characteristics Of The Antibiotic Substance Produced By Bacillus Subtilis Strain Tpb55

The purification and characteristics of the antifungal substances produced by Bacillus subtilis strain Tpb55 were researched in this article. The billogical control mechanisms of Tpb55 were also investigated. All of the conclusions were benefit for the exploitation and utilization of B. subtilis Tpb55 strain and its antifugal substances. The conclusions also provided the basis of diging out antifungal gene and choosing biologic pesticide. The results were as follows.1. The optimal medium and fermentative condition of Tpb55 was researched in this study. The results showed that the optimal medium consisted of glucose 10g, peptone 3g, MgSO4 0.5g, yeast extract 1.5g and beef extract 1.5g, water 1000ml. The optimal fermentation condition of Tpb55 was 31℃, pH7.0, 72h, 180r/ min.2. The antifungal substances of Tppb55 had strong antagonistic activity on many kinds of plant pathogenic fungi and bacteria. The substance was found to be thermostable, and its antifungal abilities were the same when it was kept at 60℃. The inhibitory activity was stable in the range of pH 5 to 10, and it was not sensitive to papain, proteinase K, pepsin and organic solvent. The antifungal proteins were water-soluble and had the activity of proteinase. The crude extraction of B. subtilis Tpb55 had strong antifungal activity on mycelial growth and conidia formation. The hypha were suppressed by antifungal substance and presented malformation like strings of beads. The top of hypha dilated to deformed spherical cell, the wall of some spherical cell were destroied. The conidium germination was inhibited by antifungal substance. Although some of them germinated, they produced deformed spherical cell.3. An antifungal protein produced by Tpb55 was isolated by the procedure of ammonium sulfate precipitation and column chromatography on DEAE-sepharose Fast Flow and Sephadex G-75. The antifungal protein isolated was proved to be purified by SDS-PAGE. Its molecular weight was 48kb approximately. The antifungal proteins had stronger antifungal activity than crude extraction on mycelial growth and conidia formation. And conidia were cracked after suppressed by antifungal protein 36 h.