Rhamnolipid production from waste cooking oil using newly isolated halotolerantPseudomonas aeruginosaM4

This study isolated a novel halotolerant Pseudomonas aeruginosa M4, that was able to degrade oil and produce rhamnolipids. Various carbon sources, nitrogen sources, inoculum ratio, pH, and temperature were tested to optimize the oil degradation conditions. The highest oil degradation rate of 85.20 % and lipase activity of 23.86 U/mL were obtained under the optimal conditions (5% inoculum at 35 °C and pH 8). The components of degradation products at different times were analyzed to explore the mechanism of oil degradation by GC-MS. Short chain fatty acid of acetic and n-butyric acids were the primary degradation intermediates. P. aeruginosa M4 had good salt tolerance up to 70 g/L. The maximum rhamnolipid concentration of 1119.87 mg/L was produced when P. aeruginosa M4 used waste cooking oil as the sole carbon source. Rhamnose precursors were synthesized from glycerol, a hydrolysis product of waste cooking oil. R-3-hydroxyalkanoate precursors were synthesized de novo using acetyl-CoA produced from β-oxidation of fatty acids. The findings show that P. aeruginosa M4 is a valuable biosurfactant producer in the treatment of waste cooking oil. Key Points P. aeruginosa isolation, oil degradation mechanism, rhamnolipid production from WCO