Optimization of fermentation parameters against Bacillus siamensis JZ1-4-10 by response surface method
[Objective]The study aimed to optimize the fermentation culture medium composition formulation and conditions of Bacillus siamensis JZ1-4-10 to improve its antibacterial activity against potato dry rot bacteria,laying a foundation for the subsequent industrial development and agricultural application of related biocontrol agents.[Method]The optimal carbon source,nitrogen source,inorganic salt and suitable concentration of B.siamensis JZ1-4-10 were screened by the single factor test.The optimal fermentation culture medium composition formulation of B.siamensis JZ1-4-10 was obtained using response surface methodology.Based on these findings,the fermentation conditions such as fermentation temperature,pH,inoculation amount,liquid volume and rotational speed of strain JZ1-4-10 were opti-mized.[Result]The optimal carbon source,nitrogen source and inorganic salt of B.siamensis JZ1-4-10 were corn flour,soy peptone and KC1 respectively.With corn flour(A),soy peptone(B)and KC1(C)as the dependent variables,and the antibacterial activity of B.siamensis JZ1-4-10 against the potato dry rot pathogen Fusarium solani as the response value,the quadratic multiple regression equation obtained for the inhibition rate(y)of B.siamensis JZ1-4-10 was y=64.02+0.4937A+2.31B-2.19C-1.17AB+138AC-1.81BC-4.73A2-4.58B2-386C2.The interactions among corn flour,soy peptone and KC1 significantly influenced the antibacterial activity of B.siamensis JZ1-4-10(P＜0.05),especially the interactions between corn flour and KC1 and between soy peptone and KC1 were extremely significant(P＜0.01).The optimum propor-tion of fermentation culture medium composition formulation by response surface analysis for B.siamensis JZ1-4-10 were as follows:0.94％corn flour,1.23％soy protein and 0.72％KC1.Under this condition,the actual value of antibacterial activity of B.siamensis JZ1-4-10 was 65.20％,which was very close to the predicted value of 64.63％.Similarly,the opti-mal fermentation conditions optimized by single factors of B.siamensis JZ1-4-10 were liquid volume of 90 mL/250 mL,inoculation amount of 1.5％,rotational speed of 160 r/min,culture temperature of 30 ℃,and pH of 7.[Conclusion]The optimized culture medium enhances the sporulation and antibacterial activity of B.siamensis JZ1-4-10,the optimized fermentation method can be used to culture the suspension of strain JZ1-4-10 in fast speed and by large amount.
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