Chemical and physical characterization of four interfacial-active rhamnolipids from pseudomonas spec. dsm 2874 grown on ƞ-alkanes

Abstract

Four extracellular glycolipids produced under growth-limiting conditions were isolated from the culture broth of Pseudomonas spec. DSM 2874.After purification by column and thick-layer chrom atography they were identified as anionic rhamnolipids.1H and 13C-NMR studies showed that two of these,β(β(2-0-β -L -rhamnopyran osyloxy)decanoyl)decanoic acid and β(β (2-0-α -L - rhamnopyranosyl-x-L -rhamnopyranosyloxy)decanoyloxy)decanoic acid, were identicalwith compounds described previously, while the other more hydrophilic compounds, β (2 -0 -α -L-rhamno- pyranosyloxy)decanoic acid and β (2-0-α-L-rhamnopyranosyl-α -L -rhamnopyran osyloxy)decanoic acid, were new com pounds. Surface and interfacial activity of the organic crude extract and of the purified components were determined in different aqueous solutions. The pH-dependence of surface and interfacial properties of the two previously described rhamnolipids (4, 20. 23) were exam ined in Teorell- Stenhagen-buffer (supplemented with 10% NaCl) at pH 3.0 and pH 9.0. All rham nolipids reduced the surface-tension from 72 to about 30 mN/m and the interfacial-tension from 42 to about 1mN / m.The critical micelle concentrations were of the order of 5 to 200 mg/1 depending on the structure of the molecule. © 1985, Walter de Gruyter. All rights reserved.