Abstract
Most of the commercially available surfactants are produced from petroleum but concern about the environment has stimulated the search for microbially produced surfactants for the industrial utilization and bioremediation of hydrocarbons. Biosurfactants are more effective, environmentally friendly, and stable than many synthetic surfactants. In previous work, we determined that biosurfactantproducing microorganisms were naturally present at contaminated soil of automobile workshops. In this study, we examine the potential of biosurfactant producers to tolerate other contaminants including heavy metals and antimicrobial compounds for the effective utilization of such microorganisms for the bioremediation of hydrocarbons at heavy metal and antimicrobial contaminated regions. For the present study seven heavy metals (NiCl2, CuSO4, CdCl2, CoCl2, CrSO4, PbSO4, ZnSO4) and four different antimicrobial compounds (Ampicillin, Streptomycin, Erythromycin, Chloremphenicol) were tested. Biosurfactant-producing bacteria were found to constitute a significant proportion (up to 35%) of heavy metal tolerant and up to 25% were found to resist antimicrobial compounds. Isolates were further characterized for colonial and cellular morphologies and analyzed through different screening methods such as oil spreading method, drop collapse method, CTAB agar plate method, BATH assay and emulsification capacity methods. Resistance against heavy metals and antibiotics has made these isolates ideal for bioremediation under stressful environmental conditions.
