Demulsifying properties of extracellular products and cells of Pseudomonas aeruginosa MSJ isolated from petroleum-contaminated soil

A strain of Pseudomonas aeruginosa isolated from a site contaminated with refined oil products exhibited demulsification capabilities against Tween 80–Span 80 stabilized oil-in-water (O/W), Tween 80-stabilized water-in-oil (W/O) model emulsions (kerosene–water), and an industrial emulsion (Daido Dairoll PA-5A). GC–MS analysis confirmed the presence of fatty acids and carbohydrates in the extracellular biodemulsifier. The demulsifying activity of cells and culture supernatants was favored by growth in media containing 1% diesel oil. There was a correlation between culture age, de-emulsification and cellular hydrophobicity, and highest activities were observed for cells and supernatants from 96-h cultures. Activity increased with addition of up to 60 mg cells or 300 μL supernatant to emulsions. The activity was relatively stable at 20–40 °C and to freezing, but was reduced by 69% by washing the cells with chloroform–methanol-water. This demulsifier has potential for application in biotreatment of emulsified oily wastewaters to promote recovery and/or degradation of oil.