Production and characterization of rhamnolipids from bioconversion of palm oil mill effluent by the halophilic bacterium Pseudomonas stutzeri BK-AB12: Production and Characterization of Rhamnolipids

This study aims to produce and characterize rhamnolipids via bioconversion of palm oil mill effluent (POME) by the halophile Pseudomonas stutzeri BK-AB12. The bacterial strain was grown in a pre-optimized mineral salt medium (MSM) containing 20%(v/v) POME, 0.2%(w/v) urea, and 5% (w/v) NaCl, at pH 7.5. Biosurfactant was produced when bacterial growth reached the end of the stationary phase to the death phase, around 96 h. In order to verify that the biosurfactant produced by P. stutzeri BK-AB12 was a rhamnolipid, a qualitative test on blue agar medium containing cethyltryacetyl bromide-methylene blue was performed. Characterization of the physicochemical properties of the purified biosurfactant revealed that it had its maximum emulsification index of about 71.4%, under the following conditions: pH 9, 15% (w/v) NaCl, and at 55 degrees C. The critical micelle concentration (CMC) of this biosurfactant was about 390 mg/L with a decrease in surface tension of water about 16 dynes/cm. Structural analysis using Fourier transform infrared and 1-D H-1 NMR reaffirmed that the biosurfactant spectrum profile was similar to rhamnolipids. Further structural analysis using high-resolution mass spectrophotometry successfully identified several new structures of rhamnolipids produced by P. stutzeri BK-AB12. (c) 2018 American Institute of Chemical Engineers Environ Prog, 38:e13007, 2019