Production and characterization of rhamnolipids from Pseudomonas aeruginosa san-ai

Abstract

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. Copyright 2012 (CC) SCS.