MEDIUM OPTIMIZATION OF Burkholderia gladioli pv. agaricicola ENHANCED THE PRODUCTION OF ANTIMICROBIAL SUBSTANCES

Numerous species in the genus Burkholderia have interesting properties for potential industrial applications including production of antibiotics, biosurfactants, bioplastics and degradation of environmental contaminants. The aim of this research was study the effect of different carbon and nitrogen sources on Burkholderia gladioli pv. agaricicola strain ICMP11096 growth and bioactivity of produced secondary metabolites against gram-positive bacterium Bacillus megaterium and plant pathogenic fungi Rhizoctonia solani. The additional carbon sources were sucrose, fructose and lactose whereas, the additional nitrogen sources were, urea, potassium nitrate and ammonium nitrate. The results demonstrated that the addition of new carbon and nitrogen sources to the minimal mineral nutrient media lead to decreasing the growth rate of studied bacterial strain and increasing the production of bioactive substances. The maximum production of bioactive substances of studied bacterial strain was obtained using ammonium nitrate and lactose. The purified filtrate of the studied bacterial strain was fractionated by High Performance Liquid Chromatography (HPLC) and the antimicrobial activity of five isolated single peaks was evaluated against gram positive bacteria B. megaterium ITM100 and gram negative bacteria Escherichia coli ITM103. The most bioactive peak was number two with 12800 and 6400 Ua.ml-1 against B. megaterium and E. coli, respectively. The obtained results suggested that the nutrient amendments can increase the production of antimicrobial substances and this may be a useful strategy for improving the biocontrol efficiency.