Improving the activity of Bacillus atrophaeus E20303 against the dry rot pathogen of potato: based on response surface methodology

Abstract:

[Background] Bacillus atrophaeus E20303 can inhibit the activity of the dry rot pathogen of potato and the response surface methodology can optimize the components of medium for fermentation and fermentation conditions of biocontrol bacteria. The optimal medium components and fermentation conditions for E20303 can serve as a reference for the preparation and application of biocontrol agents against potato dry rot. [Objective] To optimize the medium components and fermentation conditions of E20303, a strain isolated from the mud of Chaerhan Salt Lake in Qinghai with high activity against the dry rot pathogen of potato, by response surface methodology in order to improve its antifungal activity. [Methods] Single factor experiment, central composite design, and response surface methodology were used to design and optimize the medium components and fermentation conditions of E20303. [Results] The optimal components of the medium were starch 10.72 g/L, yeast powder 23.60 g/L, MgSO₄·7H₂O 16.00 g/L, CaCO₃ 1.14 g/L, KH₂PO₄ 8.00 g/L, and K₂HPO₄ 16.00 g/L. After optimization, the antifungal rate increased from 46.51% to 62.00%. The optimal fermentation conditions were liquid medium volume of 102.89 mL, pH 8.64, 28.73 ℃, rotation speed 200 r/min, culture for 3 days, and inoculum 2%. Under the conditions, the bacteriostatic rate rose from 51.15% to 72.51%. [Conclusion] The fermentation formula and fermentation conditions of E20303 with significantly improved activity against the dry rot pathogen of potato were clarified, which laid a foundation for research on the biocontrol agents against potato dry rot.

Key words:response surface methodology;fermentation medium formula;fermentation conditions;Bacillus atrophaeus;potato dry rot;antifungal activity