HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC DETERMINATION OF THE RHAMNOLIPIDS PRODUCED BY PSEUDOMONAS-AERUGINOSA

The bacterial biosurfactants 3-[3'-(L-rhamnopyranosyloxy)decanoyloxyl acid (RL-1) and 3-[3'-(2''-O-alpha-L-rhamnopyranosyl-alpha-L-rhamnopyranosyloxy)decanoic acid (RL-2) were isolated from Pseudomonas aeruginosa DSM 2659 cultures. An HPLC method was developed for the p-bromophenacyl esters of the rhamnolipids. Separation was obtained within 25 min on a RP C-18 column using a linear gradient of water-acetonitrile (30:70 to 0:100) and UV detection (265 and 320 nm). Linearity of response existed for 1.2-25 mu g of the RL-1- and 1.8-25 mu g of the RL-2-p-bromophenacyl ester (0.9-19.2 mu g RL-1 and 1.3-18.0 mu g RL-2). The reproducibility of the entire analytical method (extraction, derivatisation) was tested.