Biosurfactan Production by Bacillus sp. Isolated from Petroleum Contaminated Soils of Sirri Island

Abstract

Problem statement: Biosurfactants are active surface components produced by some bacteria and fungi. These molecules reduce surface and interfacial tension in aqueous solutions and hydrocarbon mixtures. The most important application of biosurfactants is in oil industry to enhance oil quality and facilitate oil extraction. The aim of this study was to isolate biosurfactant producing bacteria and optimize the conditions like temperature and pH for maximum biosurfactant production. Approach: Samples were collected from 8 selected points of oil contaminated soils in Sirri Island-Iran. Primary screening tests including hemolytic activity, Drop collapse technique and Oil Spreading method were preformed and species with the best results were picked for complementary screening tests like emulsification activity, foaming and surface tension measurement. Results: Totally, 160 bacteria species were isolated. During primary and complementary screening tests, 59 species showed hemolytic activity, 46 had drop collapsing ability and 18 species showed positive results in emulsification, foaming and surface tension reduction. Finally, two Bacillus sp. were found to be able to reduce surface tension more than 30 mNm^-1. Conclusion: Two strains with a high amount of biosurfactant production and emulsification ability were resulted from the present study. According to the high potential of Bacillus sp. especially for Microbial Enhanced Oil Recovery (MEOR) and Bioremediation of oil contamination we can hope that further study of the isolates characteristics and looking for new local strains can play an important role in their application in oil industry.