Submitted to: Journal of Chromatography
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/1/1999
Publication Date: N/A
Citation: Interpretive Summary: Chemicals with the properties of detergents are sometimes used to aid in the cleanup of soil and water using biological processes. These compounds act by helping to bring chemicals that are not water soluble into solution so that microbes can attack them. Most detergents are synthetic chemicals. Rhamnolipids are a class of natural compounds with detergent-like properties. They are produced by numerous strains of bacteria and help those bacteria degrade difficult substrates. The rhamnolipids produced by bacteria can have several forms, differing in the number of rhamnose moities attached to the molecule (they can have 1 or 2) or in the form of the fatty acid moities attached. Since the different rhamnolipid forms can differ in their detergent properties it is important to have an analytical technique that can be used to determine the composition of rhamnolipid mixtures produced by bacteria. This paper describes the development of a technique that uses a High-Performance Liquid Chromatograph to characterize the composition of complex rhamnolipid mixtures. This information will be useful to scientists and engineers involved in the cleanup of soil and water and to the cosmetic and food industries where rhamnolipids are used.
Technical Abstract: An 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 (RhC10:C10), 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 this last one, 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(ESI and APCI) was used to confirm their molecular weight, GC to verify their fatty acid content, and a colorimetric assay to quantify the rhamnose content.