Screening and preliminary characterization of biosurfactants produced by Ochrobactrum sp. 1C and Brevibacterium sp. 7G isolated from hydrocarbon-contaminated soils

Biosurfactant-producing bacteria were isolated from a crude-oil-contaminated soil in Hassi Messaoud (southern Algeria). Isolates were screened for biosurfactant/bioemulsifier production on different carbon sources (glucose, olive oil, and hexadecane) on the basis of their ability to reduce the surface tension. The highest number of positive isolates (19) was obtained on a medium containing hexadecane as carbon source. Culture broth from all 19 isolates emulsified motor oil and 14 exhibited high emulsion-stabilizing capacity, maintaining 50% of the original emulsion volume for 48 h. The cell-free culture broth of the two best-performing isolates (identified as Ochrobactrum sp. 1C and Brevibacterium sp. 7G) reduced the surface tension below 31.5 mN m−1. Biosurfactant produced by strains 1C and 7G exhibited tolerance, with slight variations for heat, pH, and salinity, and based on spectral features, they were glycolipids. Furthermore, they exhibited antimicrobial activities against Pseudomonas aeruginosa and Staphylococcus aureus.

► The present study focused on the selection of biosurfactant-producing strains.
► Strains 1C and 7G showed high biosurfactant production.
► Biosurfactants showed high stability against temperature, pH and salinity variations.
► Emulsification activities and antimicrobial activities of biosurfactants were assessed.
► Structural analysis suggest that biosurfactants are glycolipids.