Effect of culture medium optimization on the secondary metabolites activity of 13-6.

Fermentation products of 13-6 have antagonistic activity against devastating phytopathogenic bacerium pv. . The production of secondary metabolites was increased by optimizing the fermentation medium; using a single-factor screening test, Plackett-Burman Design, and Box-Behnken Design. The medium's final formulation for active secondary metabolites high-yield included peptone 5 g/L, glucose 4.73 g/L, MgSO·7HO 2.33 g/L, and KHPO 2.21 g/L. We compared phenazine-1-carboxylic acid (PCA) contents of 13-6 in the initial and optimized mediums through HPLC. It was found PCA contents of the optimized medium are two folds more than in the initial medium. We also detected the relative expression of five phenazine genes of 13-6 via RT-qPCR, and it was found that genes: phzB, C, S, and NO1 have more significant expression compared with the initial medium, while gene phzD has found just significant. Further, we revealed that the optimal fermentation conditions for secondary metabolites were: fermentation time 60 hours, shaking speed 160 rpm, inoculum size 3%, and the initial pH = 7.0. In the end, it was determined that the antimicrobial activity and quality of 13-6 secondary metabolites were increased by about 41.75% and 2-times, respectively, after the optimization of the fermentation medium.