Characterization of rhamnolipids produced by a Pseudomonas aeruginosa mutant strain grown on waste oils

Pseudomonas aeruginosa EBN-8 mutant rhamnolipids produced on waste oils were investigated using normal-phase thin layer chromatography and fast atom bombardment mass spectrometry. Negative ion mode mass spectra yielded [M - H](-) ions and their fragment ions, which gave some indications on the sequence of rhamnolipid biosynthesis. Five rhamnolipid homologs [viz. RC10C10 (m/z 503), RC12C10 or RC10C12 (531), RRC10C8 or RRC8C10 (621), RRC10C10 (649) and RRC12C10 or RRC10C12 (677)] were detected in four rhamnolipid combinations under the different carbon sources. The prevalence of rhamnolipids was confirmed by Fourier transform infrared and one-dimensional proton nuclear magnetic resonance. We also observed some correlations between the tensioactive characteristics and structural chemistry of the rhamnolipid surfactants.