Abstract:

In this study, a biosurfactant production and oil-degrading bacteria strain, Pseudomonas aeruginosa STQ-2, was isolated from waste cooking oil (WCO) derived from kitchen waste. The fermentation conditions were optimized to enhance the surfactant production by this strain, with the structural analysis of the products conducted by using Fourier transform infrared spectroscopy, nuclear magnetic resonance hydrogen spectroscopy, and liquid chromatography-electrospray ionization-mass spectrometry. It was shown that the optimal reaction conditions for this strain were as follows: temperature of 30 ℃, pH value of 7, WCO mass concentration of 25 g·L^-1, and ammonium chloride as the nitrogen source. When WCO was utilized as the sole carbon source, the yield of biosurfactant produced by strain STQ-2 reached 600 mg·L^-1, and the WCO degradation rate was 21.1% after 7 days of incubation under these conditions. These results demonstrated that Pseudomonas aeruginosa STQ-2 was capable of degrading WCO while simultaneously producing biosurfactant utilizing WCO as its sole carbon source. Furthermore, it was identified that the primary component of the surfactant produced by this strain was rhamnolipid, and the biosurfactant exhibited chemical stability across a pH value range of 6 to 12, NaCl mass concentrations of 20 to 140 g·L^-1, and temperature ranging from 4 to 121 ℃.

Key words: biosurfactant, rhamnolipid, Pseudomonas aeruginosa, waste cooking oil