Isolation and screening of potential biosurfactant-producing bacteria from used engine oil-contaminated soil

Abstract

Biosurfactants are compounds with surface activity and emulsification ability that are produced by an extensive variety of microorganisms such as bacteria, actinobacteria, algae and fungi. This study was done in order to isolate and screen for potential biosurfactant-producing bacteria from soil contaminated with used engine oil. Mineral salt medium (MSM) with used engine oil as the sole carbon source was used to isolate potential biosurfactant producing bacteria. The potential isolates were screened through drop collapse test, oil spread test and emulsification index test. There were 26 isolates that have been recovered from the enrichment culture. Three isolates namely 2c, 2k and 2m were further identified as the potential biosurfactant producers based on drop collapse, oil displacement and emulsification index tests. Then, the selected isolates were grown in MSM supplemented with used engine oil as sole carbon source to determine the production of biosurfactant. Isolate 2k produced 15.1 g/L biomass which was the highest as compared to the other isolates. In contrast, the highest yield of biosurfactant (0.029 g biosurfactant/g biomass) was produced from isolate 2m eventhough the biomass was lower than isolate 2k.