Biosurfactant Production by Strains of Azospirillum Isolated from Petroleum-Contaminated Sites

Some microorganisms can produce biotensoactive when in contact with hydrocarbons, which favours micelle formation, allowing microbial cells to metabolise them effectively. In this study, we evaluated the capacity of nitrogen-fixing (NFB) and hydrocarbonoclastic bacterial strains to generate biotensoactive. The sampling site was in a flood plain of the Chico Zapote River, on the low basin of the Tonalá River in Tabasco, Mexico. Rhizospheres and soil contaminated by oil were collected, and the concentration of oil and botanic samples were determined for their taxonomic classification. The collected rhizosphere oil was seeded into Congo red cultures to obtain Azospirillum (NFB) bacteria. The NFB strain was placed in liquid mineral medium with oil as the only carbon source to identify the hydrocarbonoclastic strains. Biochemical and physiological evaluations determined that the species were Azospirillum brasilense and Azospirillum lipoferum. The strains were placed into Kim medium for generating a biosurfactant. The biosurfactant produced by A. brasilense showed an emulsion stability of 229 min, yield of 0.1375 g L−1, emulsion capacity of 80 % and superficial tension of 38 mN m−1, and while the biotensoactive produced by A. lipoferum had an emulsion stability of 260 min, yield of 0.22 g L−1, emulsion capacity of 90 % and superficial tension of 35.5 mN m−1.