Nagaraj Nagabalaramesh Sirisha Mallula Lakshmi Krishnan Kannabiran Department of Biotechnology, School of Bio Sciences and Technology Vellore Institute of Technology, Vellore - 632014, Tamil Nadu, India Proceedings of the International Academy of Ecology and Environmental Sciences ISSN 2220-8860 http://www.iaees.org/publications/journals/piaees/online-version.asp 2025 15 1 1 9 International Academy of Ecology and Environmental Sciences Hong Kong 6 June 2024 15 July 2024 1 March 2025 bioremediation biosurfactant marine bacteria petroleum hydrocarbons salinity Petroleum hydrocarbons (PHCs) are one of the most hazardous pollutants affects human and animal health and alters the nature of the ecosystem. The aim of this study is to isolate the PHCs degrading bacteria and to assess its degrading potential. Used engine oil (UEO) was used as a sole carbon source for the growth of the bacteria isolated from marine soil sample. Biodegradation efficiency of bacterial isolates on UEO was determined by gravimetric analysis. Biosurfactant production by the PHC degrading isolate was assessed by drop collapse test, oil displacement assay and emulsification index measurement. The isolate was identified by morphological and biochemical characterization. Salt tolerance of the isolate on UEO biodegradation was studied by gravimetric analysis. Gravimetric analysis revealed that the isolates VITSK5 and VITSK6 showed 51.35% and 63.5% degradation of UEO respectively. The isolate VITSK6 showed comparatively higher biosurfactant production than VITSK5. VITSK5 showed increased UEO degrading efficiency with increase in salt concentration. Biofilm formation test showed that VITSK5 is a moderate biofilm producer and VITSK6 is a weak biofilm producer. http://www.iaees.org/publications/journals/piaees/articles/2025-15(1)/biosurfactant-mediated-degradation.pdf