Isolation and identification of the antagonistic strain DM-54 of Bacillus amyloliquefacien against Verticillium dahliae, and optimization of antifungal protein producing conditions

Abstract

The strains capable of resistance against Verticillium dahliae Kleb were isolated and screened from the soils of cotton fields from several different provinces in China. A strain, coded DM-54, with a rather high antagonistic activity was obtained. Its morphological characteristics, physiological and biochemical properties and a 16 S rDNA sequence of this strain were further studied. The DM-54 strain was finally identified as a kind of Bacillus amyloliquefacien. Through a single factor experiment and an orthogonal experiment, the optimal shaking flask fermentation condition of strain DM-54 was found to be: media composed of 5% dextrin, 3% soy peptone, 0.02% MgSO4, 0.01% CaCl2, initial pH 7.0 and 10% inoculum volume, media volume 30/250 (mL/mL), fermentation temperature at 32°C, rotating speed 200 r·min−1, fermentation time of 48 h. Its antagonistic activity was distinguished to be elevated, at about 39.9%. Our research offers an effective means for the massive production of antagonistic proteins.