Optimization of fementation medium and conditions of Bacillus subtilis PTS-394

The Plackett-Burman(PB) design and response surface methodology were adopted to optimize the liquid fermentation medium and conditions of the biocontrol agent of Bacillus sublitis PTS-394.By the statistical analysis of PB design,the significant composition factors affecting the yielding capacity were corn starch,soybean powder,yeast extract.And their optimal ratio was obtained according to the evaluation by the response surface model.Then the production of spores and antibacterial bandwidth 4.43×109 cfu·mL-1 and 6.20mm,verified by flask fermentation experiments,were 104.7% and 44.8% higher than that of initial medium.The significant condition factors were temperature,pH and medium volume.Then the bacteria content and antibacterial bandwidth increased 39.2% and 46.0% under the optimized conditions.The result was consistent with the data of flask fermentation experiments.So the model generated by the RSM was proved to be effective and available.