Optimition of fermentation conditions of streptomyces strain D2, an antagonistic strepomyces against muskmelon fusarium wilt

ObjectiveThe present study aimed to explore an optimal fermentation condition of streptomyces strain D2 that was against muskmelon fusarium wilt so as to provide scientific basis for the establishment of the strain fermentation method and industrial production.MethodThe viable bacteria number of strain D2 was taken as the indicator of the inves-tigation,and influencing factors included corn powder content,soybean powder content,pH,rotation speed,inoculation amount and temperature. The fermentation condition of strain D2 was optimized by employing the combination of Plackett-Burman(P-B)design,uphill path method,central composite design(CCD)and response surface method.ResultThe re-sults showed that corn powder content,soybean powder content and temperature significantly affected viable bacteria num-ber of strain D2(P<0.05). The regression model of viable bacteria number of strain D2 was:Y=8.28757+0.12344X1+0.21477X2+0.06184X3-0.05929X12-0.09817X22-0.14942X32 ,and the viable bacteria number was 2.99×108 CFU/mL in theo-ry. The optimal fermentation conditions for strain D2 was:corn powder content 39.08 g/L,soybean powder content 39.19 g/L and culture temperature 37.4℃. Under these conditions,the viable bacteria number of strain D2 was 3.01 × 108 CFU/mL, which was close to the theoretical content,but was extremely significant higher than the viable bacteria number(1.0 × 106CFU/mL)obtained by using mediumⅡwithout optimization(P<0.01).ConclusionThe optimum fermentation culture technique for strain D2 optimized by response surface method can effectively improve the viable bacteria number. The via-ble bacteria number predicted by regression model is close to the actual number fermented under the optimized fermenta-tion condition. Therefore,this model can be used to predict the fermentation of D2 strains in practical production.