High-performance liquid chromatography method for the characterization of rhamnolipid mixtures produced by pseudomonas aeruginosa UG2 on corn oil

A HPLC method was developed to quantify rhamnolipid species in a bacterial biosurfactant mixture. The biosurfactant mixtures containing mainly 3-[3'-(L-rhamnopyranosyl-oxy)decanoyloxy]decanoic acid (RhC10C10), 3-[3'-(2'-O-alpha-L-rhamnopyranosyl-oxy)decanoyloxy]decanoic acid (Rh2C10C10), 3-[3'-(2'-O-alpha-L-rhamnopyranosyl-oxy)decanoyloxy]dodecanoic acid (Rh2C10C12), and a dehydrogenated variety of the latter, 3-[3'-(2'-O-alpha-L-rhamnopyranosyl-oxy)decanoyloxy]dodecenoic acid (Rh2C10C12-H2), were isolated from Pseudomonas aeruginosa UG2 cultures grown on corn oil as sole carbon. The rhamnolipid species were identified and quantified after their derivatization to the corresponding phenacyl esters. To confirm the reliability of the HPLC method, the biosurfactant mixtures and the HPLC isolated species were further analyzed. Mass spectroscopy (electrospray ionization and atmospheric pressure chemical ionization techniques) was used to confirm their molecular mass, gas chromatography to verify their fatty acid content, and a colorimetric assay to quantify the rhamnose content.