The research was carried out in order to identify the optimal parameters for the cultivation of Pseudomonas chlororaphis BZR 245-F and Pseudomonas sp. BZR 523-2 bacteria, which form the largest number of bacterial cells and realize a high potential for the synthesis of antifungal metabolites, for their subsequent inclusion in the technological regulations for the production of biofungicides based on these bacteria. The experimental scheme provided for the study of the following cultivation parameters: temperature (+20, +25, +30, +35°C) and acidity (pH 3.0; 6.0; 7.0; 8.0). The titer value of bacterial cells was determined by the Koch method. The analysis of antifungal metabolites was performed by thin-layer chromatography and bioautography. The amount of metabolites produced by bacteria was assessed by visual assessment of thin-layer chromatograms and growth inhibition zones of the test culture of the fungus on bioautograms. For P. chlororaphis BZR 245-F optimal conditions for maximum biomass production (4.72 × 1011 CFU/mL) and enhanced synthesis of antifungal metabolites, including orange pigment (Rf 0.45) and phenazine compounds (Rf 0.52), are a temperature of 25°C and pH 6.0–10.0 (with a peak at pH 6.0 and 8.0), and the antifungal activity is most pronounced at 25–30°C. Strain Pseudomonas sp. BZR 523-2 shows the highest titer (9.7 × 1011 CFU/mL) and increased production of phenazine metabolites (Rf 0.52) at a temperature of 25–30°C and pH 6.0–8.0, and also produces phenazine in significant amounts at pH 8.0 and 10.0. At the same time, its overall antifungal activity, although inferior to P. chlororaphis BZR 245-F, is maximal at a temperature of 30°C. Both strains synthesize various active compounds, with phenazine structures making the main contribution to their antifungal effect.
Sidorova et al. (Mon,) studied this question.
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