Characterization of Biosurfactant Produced by a Novel Strain ofPseudomonas aeruginosa, Isolate ADMT1

Abstract

AbstractSeveral biosurfactant‐producing bacterial strains were isolated from petroleum‐contaminated soil. The isolate ADMT1, identified as a new strain ofPseudomonas aeruginosa, was selected for further studies on the basis of oil displacement test and emulsification index (E24). The optimal parameters for production, determined by employing Box–Behnken design, were temperature 36.5 °C and pH 7. The environmental isolate ADMT1 produced significant amount of biosurfactant (1.7 g L−1in 72 h) in minimal salt medium (MSM) using dextrose as the sole carbon source. The E24 value and critical micelle concentration (CMC) of the biosurfactant was 100% and 150 mg L−1, respectively. At CMC, the surface tension of water was reduced to 28.4 mN m−1. The biosurfactant exhibited hemolytic activity and antibacterial activity against 8 reference strains of pathogenic bacteria, including 2 methicillin‐resistantStaphylococcus aureusstrains (MRSA ATCC 562 and MRSA ATCC 43300), with minimum inhibitory concentration (MIC) of 0.4 and 0.2 mg mL−1, respectively. The structure of biosurfactant was characterized by FTIR,1H, and13C NMR spectroscopy. 7 di‐rhamnolipid (RL) congeners were identified in the biosurfactant by ultraperformance liquid chromatography–mass spectrometry analysis. The major congeners, which constituted 67% of the RL mixture, included Rha‐Rha‐C10‐C10, Rha‐Rha‐C12‐C10, and Rha‐Rha‐C12:1‐C10. The minor congeners were Rha‐Rha‐C10‐C8, Rha‐Rha‐C10:1‐C10, Rha‐Rha‐C10‐C14:1, and Rha‐Rha‐C10‐C14. The congener Rha‐Rha‐C10‐C14is being reported for the first time from any species ofPseudomonas. The high surface activity and E24 value make the ADMT1‐RL a potential candidate for its use in detergents, environmental bioremediation, and as an emulsifier in the food industry.