(669i) Oil Spill Dispersion with Food-Grade Amphiphiles: Formation of Oil-Bacteria Agglomerates during Oil Biodegradation

Food grade amphiphilic molecules, such as soybean lecithin and polyethoxylated surfactants, have been shown to be effective emulsifiers and capable as substitutes for conventional surfactants (e.g. dioctyl sulfosuccinate or DOSS) in the design of new dispersant systems. A key requirement of a dispersant system is that it facilitate bacterial adhesion to dispersed oil droplets to promote oil biodegradation. We have employed a microplate-based approach coupled with respirometry and microscopy studies to examine the interfacial and colloidal behavior associated with the adhesion of Alcanivorax borkumensis, an oil-eating bacterium commonly found near oil spills, to oil dispersed by lecithin/Tween-80 mixtures. Using hexadecane as a model oil, we show that increasing oil concentration (50 to 1000 mg/L) and bacteria concentration drive the formation of oil-bacteria agglomerates that sediment over several days. Microscopy analysis shows that the bacteria remain viable (alive) once adhered to the oil-water interface and form a dense biofilm with a fibrous network of exopolymeric substances. This work complements our research on the dispersion effectiveness of lecithin and lecithin/Tween-80 mixtures, and confirms that such mixtures can promote oil biodegradation.