Inhibitory activity of Rhamnolipid produced by Pseudomonas aeruginosa NH22 against Rhizoctonia solani

In the present study, isolation and identification of microorganisms from rhizospher of garden soil with biosurfactant producing ability and characterization of biosurfactants were studied. The results exhibited capability of four isolates for biosurfactant production among six isolates. The isolate Pseudomonas aeruginosa NH22 showed a better emulsifier producer, therefore it selected for biosurfactant production and antifungal activity in the present study. Biochemical analysis of partially purified bioemulsifier demonstrated that the biosurfactant contains mono, and di- rhamnolipid with Rf values of 0.82 and 0.32 respectively. Rhamnolipid efficiency tested for antifungal activity by determination percentage reduction of radial growth, fresh and dry weight and laccase activity of fungus. Maximum reduction in radial growth 76%, and reduction of biomass obtained at rhamnolipid concentration of 1000 μg/ ml. Maximum laccase activity obtained 0.921 U/ml also at rhamnolipid concentration of 1000 μg/ ml, while reduction about 21% of the enzyme activity recorded at higher rhamnolipih concentration of 1500 μg/ ml. The critical micelle concentration estimated to be 200 mg/l, which led to reduce surface tension value of the culture to34 mN/m.