Role of phenanthrene in rhamnolipid production by P. putida in different media

Abstract

The role of phenanthrene in rhamnolipid production by P. putida in eight media with different culture conditions was investigated. Cultures using Fe2SO4.7H2O, KH2PO4, NH4Cl, yeast extract, glucose, and corn oil, with and without 200 mg l(-1) of phenanthrene, were evaluated under shaking for rhamnolipid production through a 2(7-4) fractional factorial experimental design. The biosurfactant production, decrease in the surface tension of the broth and the total cell growth in media without phenanthrene were affected significantly (p < 0.001) by yeast extract, glucose, corn oil and NH4Cl, and in media with phenanthrene by glucose and yeast extract. The non polar fraction of the biosurfactant in all media was composed of linoleic (C18:2), arachidic (C20:0) and behenic (C22:0) fatty acids. The medium with phenanthrene (200 mg l(-1)), Fe2SO4.7H2O (5 x 10(-4) g l(-1)), KH2PO4 (0.2 g l(-1)), glucose (50 g l(-1)), yeast extract (1 g l(-1)), corn oil (2% vol), and NH4Cl (1 g l(-1)), shaken at 150 rpm at 37 degrees C, and pH 7.0, presented the highest biosurfactant production. For this medium the surface tension decreased by 35.9 mN m(-1) in relation to the initial value, and only this medium showed an emulsion capacity of 20%. The polar fraction (Rhamnose) in media 1, 3, 7 and 8 with phenanthrene was c.a 100%, in contrast to those without phenanthrene where this fraction was undetectable.