title: Evaluation of screening methods for demulsifying bacteria and characterization of lipopeptide bio-demulsifier produced by Alcaligenes sp.
abstract: In this paper, surface tension measurement, oil-spreading test and blood-plate hemolysis test were attempted in the screening of demulsifying bacteria. After the comparison to the screening results obtained in demulsification test, 50 mN/m of surface tension of culture was proposed as a preliminary screening standard for potential demulsifying bacteria. For the identification of efficient demulsifying strains, surface tension level was set at 40 mN/m. The detected strains were further verified in demulsification test. Compared to using demulsification test alone as screening method, the proposed screening protocol would be more efficient. From the screening, a highly efficient demulsifying stain, S-XJ-1, was isolated from petroleum-contaminated soil and identified as Alcaligenes sp. by 16S rRNA gene and physiological test. It achieved 96.5% and 49.8% of emulsion breaking ratio in W/O and O/W kerosene emulsion within 24h, respectively, and also showed 95% of water separation ratio in oilfield petroleum emulsion within 2h. The bio-demulsifier was found to be cell-wall combined. After soxhlet extraction and purification through silicon-gel column, the bio-demulsifier was then identified as lipopeptide biosurfactant by TLC and FT-IR.
authors.affiliation: College of Environmental Science and Engineering, State Key Laboratory of Pollution Control and Resource Reuse, Tongji University, Shanghai, China. hxf@mail.tongji.edu.cn
authors.forename: Xiang-Feng
authors.initials: XF
authors.lastname: Huang
authors.forename: Jia
authors.initials: J
authors.lastname: Liu
authors.forename: Li-Jun
authors.initials: LJ
authors.lastname: Lu
authors.forename: Yue
authors.initials: Y
authors.lastname: Wen
authors.forename: Jing-Cheng
authors.initials: JC
authors.lastname: Xu
authors.forename: Dian-Hai
authors.initials: DH
authors.lastname: Yang
authors.forename: Qi
authors.initials: Q
authors.lastname: Zhou
mesh_terms: D000421:Alcaligenes / Q000145:classification / Q000302:isolation & purification* / Q000378:metabolism*; D045703:Emulsifying Agents / Q000737:chemistry*; D004655:Emulsions / Q000737:chemistry; D006461:Hemolysis / Q000502:physiology*; D006801:Humans; D055666:Lipopeptides / Q000737:chemistry*; D013500:Surface Tension; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: D045703:Emulsifying Agents; D004655:Emulsions; D055666:Lipopeptides; D013501:Surface-Active Agents