Selection of biosurfactan/bioemulsifier-producing bacteria from hydrocarbon-contaminated soil

Viramontes-Ramos, SabinaPortillo-Ruiz, Martha CristinaBallinas-Casarrubias, María de LourdesTorres-Muñoz, José VinicioRivera-Chavira, Blanca EstelaNevárez-Moorillón, Guadalupe Virginia

Petroleum-derived hydrocarbons are among the most persistent soil contaminants, and some hydrocarbon-degrading microorganisms can produce biosurfactants to increase bioavailability and degradation. The aim of this work was to identify biosurfactant-producing bacterial strains isolated from hydrocarbon-contaminated sites, and to evaluate their biosurfactant properties. The drop-collapse method and minimal agar added with a layer of combustoleo were used for screening, and positive strains were grown in liquid medium, and surface tension and emulsification index were determined in cell-free supernantant and cell suspension. A total of 324 bacterial strains were tested, and 17 were positive for the drop-collapse and hydrocarbon-layer agar methods. Most of the strains were Pseudomonas, except for three strains (Acinetobacter, Bacillus, Rhodococcus). Surface tension was similar in cell-free and cell suspension measurements, with values in the range of 58 to 26 (mN/m), and all formed stable emulsions with motor oil (76-93% E24). Considering the variety of molecular structures among microbial biosurfactants, they have different chemical properties that can be exploited commercially, for applications as diverse as bioremediation or degradable detergents.

1. hydrocarbon contamination
2. bioemulsifiers
3. soil microbiota
4. biosurfactants