(669j) The Role of Bacterial Biofilm in Particle-Stabilized Oil-in-Water Emulsions: Implications to the Biodegradation of Oil Spills

The formation of oil-in-water emulsions from spilled oil and produced water has been attributed to the presence of natural suspended particles that stabilize the oil-water interface. While this phenomenon has been well-studied, the role of biofilm produced by oil degrading bacteria in these systems is yet to be fully understood. We use a model system of flat sheet clays (kaolinite) to form particle stabilized emulsions and contact the oil droplets with a hydrocarbon degrading bacterial organism (Alcanivorax borkumensis). Optical microscopy and cryo-SEM imaging of the microbial biofilm in the presence of particles shows a dense aggregate of cells embedded in the biofilm and evidence of biofilm bridging between particles. Surface engineering of the clay sheets through carbonization to optimize the contact angle, improves emulsion stability. It is found that the biofilm bridging that lead to particle and droplet aggregation leads to the natural phenomenon of “marine snow” and a partial sinking of oil that has been reported in the environment of oil spills. We thus conclude that natural and engineered particulates adhere at oil-water interface resulting in significant and rapid sedimentation only upon microbial activity, specifically due to biofilm formation on oil surface decorated by particles. The results of our work provide insight into interactions between oil degrading biofilm producing marine organisms and clay particles at solid stabilized oil interfaces.