Isolation of Biosurfactantproducing Bacteria from Petroleum-contaminated Soils of the Sirri Island

Biosurfactants are active surface components produced by some bacteria and fungi. These molecules reduce surface and interfacial tension in aqueous solutions and biphasic systems respectively. The most important application of biosurfactants is in oil industry to enhance oil recovery. The aim of this study is to isolate biosurfactant-producing bacteria and optimize the conditions such as temperature and pH for maximum biosurfactant production. Samples were collected from 8 selected points of oil-contaminated soils in the Sirri Island. Overall, 160 strains of bacteria were investigated in terms of isolation and morphological and gram stain. 59 strains had hemolytic activity and 46 strains had oil collapsing ability. Also, the results of oil displacement test were positive for 20 strains. Afterwards, 18 strains were selected and complementary tests such as foam formation and emulsification activity and surface tension were performed on them. Finally, two strains were found to be able to reduce surface tension more than 30 mNm-1 at 37 °C and a pH value of 7.0. Two strains with a high amount of biosurfactant production and emulsification ability were obtained in the present study. Regarding the high potential of the biosurfactant produced, it is suggested that it should be used in commercial applications such as enhanced oil recovery, bioremediation of soil and marine environments, and food industries.