Characterization of Biosurfactants Produced by a Novel Hydrocarbonoclastic Bacterial Strain Rhodococcus ruber N19 Isolated From River Sediment

Biosurfactants are eco-friendly, surface-active compounds produced by microorganisms that have significant industrial and environmental applications due to their biodegradability and low toxicity. This study focuses on the production and characterization of biosurfactants by bacterial strain N19, a novel hydrocarbonoclastic bacterium isolated from Soummam River sediment. The bacterium was cultured in mineral salt medium supplemented with crude oil to stimulate biosurfactant production. Surface tension reduction (23.14 ± 0.12 mN/m), emulsification index (72.13% ± 1.15%), and oil displacement (4.2 ± 0.75 cm) tests confirmed the presence of an effective biosurfactant. Further phenotypic and molecular identification methods, including 16S rRNA sequencing, established the strain's identity as Rhodococcus ruber N19. This strain produced 7.92 ± 0.02 mg/mL biosurfactant. Structural characterization using thin layer chromatography (TLC), Fourier-transform infrared (FTIR) spectroscopy, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS), and liquid chromatography–tandem mass spectrometry (LC–MS/MS), and nuclear magnetic resonance (NMR) analyses revealed that the biosurfactant produced by this strain is a lipopeptide. The nonhemolytic properties, combined with the ability to lower surface tension and exhibit strong emulsification and oil displacement activities, highlight the potential of this biosurfactant for bioremediation, petroleum industry applications, and biomedical use.