Production and characterization of rahamnolipid from strain Pseudomonas aeruginosa san ai

The production and characteristics of rhamnolipid biosurfactant obtained by the strain Pseudomonas aeruginosa san-ai were investigated. With regard to the carbon and nitrogen sources, several media were tested to enhance the production of rhamnolipids. Phosphate-limited proteose peptone–ammonium salt (PPAS) medium supplemented with sunflower oil as a source of carbon and mineral ammonium chloride and peptone as nitrogen sources greatly improved the production of rhamnolipid, from 0.15 on basic PPAS (C/N ratio 4.0) to 3 g L-1 on optimized PPAS medium (C/N ratio 7.7). Response surface methodology analysis was used for testing the effect of three factors, i.e., temperature, concentration of carbon and nitrogen source (mass %), in the optimized PPAS medium on the production of rhamnolipid. The isolated rhamnolipids were characterized by infrared (IR) spectroscopy and electrospray ionization mass spectrometry (ESI–MS). The IR spectra confirmed that the isolated compound corresponded to the rhamnolipid structure, whereas MS indicated that the isolated preparation was a mixture of mono-rhamno-mono-lipidic, mono-rhamno-di-lipidic and di-rhamno-di-lipidic congeners.