Isolation and production of biosurfactant from Pseudomonas aeruginosa   isolated from Iranian southern wells oil

In this study one hundred and fifty two bacterial strains were isolated from oil contaminated. Hemolysis was used as a criterion for the primary isolation of biosurfactant producing-bacteria. Fifty five strains had haemolytic activity, among -them twelve strains were good biosurfactant producers by measuring surface tension and emulsification activity. Two microorganisms showed the highest biosurfactant production when grown on paraffin and glycerol as sole carbon source. As a result of biosurfactant synthesis the surface tension of the medium were reduced from 73 mN/m to values below 32 mN/m.A rhamnolipid producing bacterium, P.aeruginosa isolate from oil wells in the southern of Iran. Isolated strain was identified by morphological, biochemical, physiological. The identified Pseudomonas aeruginosa

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confirmed by Persian type culture collection. Glycolipid production by isolated bacterium using different carbon (gasolin, paraffin oil, glycerol, whey) and nitrogen sources (NaNO₃, (NH₄)₂SO₄ and CH₄N₂O) was studied. Biosurfactant production was quantified by surface tension reduction, critical micelle dilution (CMD), emulsification capacity (EC), and ThinLayerChromatogeraphy. The best result were obtained when using glycerol as a C/N ratio of 55/1 and use of sodium nitrate as nitrogen source resulted in higher production of the rhamnolipid, expressed by rhamnose (4.2 g/l) and by the yield in relation to biomass (Yp/x = 0.65 g/g). Additionally, physical-chemical characteristics of the spent broth with and without cells were studied, providing a low critical micelle concentration of 19 mg/l and surface tension was reduced to 20 mN/m (%).

Keywords
production of biosurfactants, wild type, glycolipids, rhamnolipids, Pseudomonas aeruginosa, surface-active substances