Production and characterization of a new biosurfactant from Pseudomonas cepacia grown in low-cost fermentative medium and its application in the oil industry

Abstract

The production of a biosurfactant by Pseudomonas cepacia CCT6659 was studied in a low-cost medium formulated with 2% waste frying oil, 3% corn steep liquor and 0.2% NaNO3 for 60 hs at 28 °C and 250 rpm. Biosurfactant production was growth associated, as indicated by the growth and biosurfactant production kinetics. The surface tension of the medium was reduced from 65 mN/m to less than 25.5 mN/m. The properties of the biosurfactant that was separated by acid precipitation and solvent extraction were investigated and its critical micelle concentration was determined as 600 mg/L. Preliminary chemical characterization revealed the anionic nature of the biosurfactant. The biosurfactant was characterized by Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1 H NMR) and gas chromatography and mass spectroscopy (CG-MS). Biosurfactant demonstrated good surface tension reduction capacity and emulsifying activity with motor oil (up to 90%). The biosurfactant also demonstrated stability during exposure to high temperatures (up to 120 °C for 15 min), high salinity (12% NaCl) and a wide pH range (2–12). The crude biosurfactant was not toxic to the microcrustacean Artemia salina or two Brassica oleracea plant species. The crude biosurfactant was effective at recovering up to 75% of the residual oil from sand samples, at displacing oil (81%) and recovering up to 90% of motor oil from the walls of beakers. These results indicate the potential value of this biosurfactant for application in the oil industry, especially in enhanced oil recovery, tank cleaning and the bioremediation of spills at sea and soil.