Sudies were carried out to evaluate the surface active properties of rhamnolipid B [2-O- (2-O- α-decenoyl-α-L-rhamnopyranosyl) - α -L-rhamnopyranosyl-β-hydroxydecanoyl- β-hydroxydecanoic acid] and its precursor A as microbial biosurfactants produced by the hydro-carbon-assimilating bacterium, Pseudomonas aeruginosa BOP 100. The micelle formation of the sodium salts of rhamnolipids was confirmed by the detection of critical micelle concentration s (cmc) of A : 6.22 × 10-5, B : 1.50 × 10-4M (fluorescence intensity of ANS) and by micellar weight determinations of A : 38000, B : 7000 (light scattering), in spite of the bulky and complicated structures of the micelles, consisting of alternate hydrophobic and hydrophilic portions in contrast to synthetic surfactants. The γ cmc values of the sodium salts of A and B were 28 mN/m, while their interfacial tension was 0.2 and 3.2 mN/m at the interface between 0.1% solution and kerosene. Moreover, highly efficient gross effects were also noted particularly in dispersing, emulsifying, foaming and penetrating action. From these findings rhamnolipids may be concluded to have large surface activity and polyfunctionality on the basis of the amphiphiles as membranous constituents.
