Abstract
The current study aimed to examine 271 bacterial isolates from the plant rhizosphere and oil-contaminated soil for the ability to produce extracellular bioemulsifiers. The bacterial isolates were screened for bioemulsifier production using several tests, including oil displacement, parafilm M destabilization, droplet collapse, and the emulsification index (E-24). The most effective strains were characterized by 8 isolates displaying an E-24 index greater than 60%. Among these, 6 strains isolated from plant rhizospheres demonstrated the ability to form mucus on solid media. The remaining two strains, Z2 and D1, were isolated from oil-contaminated soils and exhibited robust growth in a medium supplemented with oil and diesel. Surface tension was measured using the Wilhelmy plate method, finding low surface tension values of 57.6 ± 0.6 and 55.6 ± 0.6 mN/m for the culture supernatants of strains Z2 and D1, respectively. Further, a study on the cell hydrophobicity of strains Z2 and D1 revealed values above 70%, indicating high hydrophobicity. Strains Z2 and D1 were selected for their high emulsifying activity in the presence of edible oils and petroleum hydrocarbons, suggesting their potential as bioemulsifier producers.