Abstract: Biosurfactant-producing bacteria were isolated from transformer oil-contaminated soil. The strain was identified as Pseudomonas aeruginosa PU1 based on its molecular characterization by 16S rRNA gene sequencing. The extraction of biosurfactant was done by acid precipitation method using 2 N hydrochloric acid and further purified by silica-gel column chromatography. The highest rhamnolipid biosurfactant production (8.92 ± 0.08 g/L) was obtained using molasses (6%, w/v) and ammonium nitrate (5%, w/v). The purified biosurfactant showed a reduction in surface tension of water from 70.23 mN/m to 29.77 mN/m at a concentration of 30 mg/L. The degradation of various oils by P. aeruginosa PU1 through gravimetric method showed maximum degradation of used transformer oil (95.55 ± 2.70%) followed by diesel oil (94.36 ± 1.86%), kerosene (76.17 ± 1.62%) and petroleum oil (66.03 ± 2.91%) in 10 days of the incubation period. The functional groups were characterized by Fourier transform infrared spectroscopy (FT-IR) and proton nuclear magnetic resonance (1H NMR). The liquid chromatography-mass spectrometry (LC-MS) analysis showed six different rhamnolipid congeners with pseudomolecular ions (m/z) of 305, 361, 451, 505, 532, and 621. X-ray diffraction (XRD) analysis and the thermal analysis showed crystalline nature and thermal stability of the biosurfactant. The stability study of the biosurfactant reveals that the emulsifying activity was much stable at various ranges of temperature (4–120 ○C), pH (2–12), and NaCl concentration (2–10%, w/v) even on the 7th day. The purified biosurfactant PU1 was found to be effective in oil recovery and showed 68.53 ± 3.07% of oil recovery in the sand pack column under saline condition, which was higher than anionic surfactant sodium dodecyl sulfate (SDS). The physico-chemical properties and the stability studies of the biosurfactant suggested that it has enormous potential in oil recovery in the soil contaminated with the oils.
Keywords: Pseudomonas aeruginosa PU1, biosurfactant, rhamnolipid, emulsifying activity, oil recovery.
Title: Physico-chemical characterization of biosurfactant secreted by Pseudomonas aeruginosa PU1 with its stability studies and application in microbial enhanced oil recovery
Author: Latha Domdi, Avinash Kant Lakra, Younus Mohd Tilwani, Venkatesan Arul
International Journal of Life Sciences Research
ISSN 2348-313X (Print), ISSN 2348-3148 (online)
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