Comparison of effect of organic media on wild-type and mutation-type population of biocontrol bacterium Pseudomonas fluorescens VUPf5

In this study, the growth of two strains Pseudomonas fluorescens VUPf5 and P. fluorescens VUPf5-1 (mutant bacterium similar to mutants of regulatory GacS/GacA system) were evaluated in the organic media. This spontaneous mutation blocked biosynthesis of the antimicrobial compounds hydrogen cyanide, phenazine and exoprotease by biocontrol strain Pseudomonas fluorescens VUPf5. By using organic media amendments by zinc sulfate or without it considered to reduce the growth of mutants. With the aim of increasing VUPf5 population and decreasing VUPf5-1 population six carbon sources (sugar beet molasses, starch, potato, date, sugar and apple), three nitrogen sources (soybean, urea, ammonium sulfate) and one nitrogen-carbon source (wheat germ) were assessed. Medium 13B (molasses, wheat germ, soybean, sugar, apple, manganese sulfate) was more effective for growth of strain VUPf5 (5.56× 1010 cells per ml) compared other treatments and population difference was significant. Medium 1D (molasses, wheat germ, soybean, sugar, apple, zinc sulfate) greatly caused to reproduction reduction in strain VUPf5-1. The results could provide a reliable basis for optimized mass multiplication of biocontrol agent in fermentation processes.