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This paper describes the development of a protein-based foam formulation and subsequent investigations into its suitability to enhance the degradation of a model hydrocarbon (n-hexadecane) using novel bench-scale soil microcosms. High-density protein-based foam concentrates based upon those developed by the fire-fighting industry were selected for experimental investigation. Using crude protein hydrolysate as a starting material, a foam formulation was developed with properties suitable for bioremediation studies. This formulation incorporated eight hydrocarbondegrading bacteria that had been selected for their ability to degrade hexadecane. In addition to their ability to utilize n-hexadecane, the bacteria were tested for compatibility with the foam formulation and each other. Seven individual Acinetobacter spp. and a Pseudomonas species were selected for use in the consortium based on these criteria. The use of this "bioactive foam" led to enhanced n-hexadecane degradation when compared to controls without foam. Following 7-d incubation, 60% of the n-hexadecane remained in the soil column using a foamed formulation, as compared to 90% with a nonfoamed control. In a subsequent experiment over a 15-d time course, the authors observed significantly greater n-hexadecane degradation in response to oxygenated bioactive foam treatment.

Aims: A microbe‐colonized gas–liquid foam formulation has been previously shown to provide enhanced biodegradation capabilities in soil microcosms. The present study considers the reservoir properties of this foam and how this affects hydrocarbon degradation rates. Methods and Results: Oxygen solubility in protein hydrolysate solutions draining from aerated and oxygenated foams was measured. The suitability of oxygenated foam to enhance the degradation of n‐hexadecane in soil microcosms was assessed. Sorption of bacterial isolates at the gas–liquid interface was also investigated using a range of microscopy techniques. Conclusions: Oxygenated bioactive foam enhanced biodegradation rates by improving oxygen availability and transfer. Biodegradation of n‐hexadecane was also stimulated by the protein hydrolysate used and by the inclusion of known bacterial hydrocarbon‐degrading bacteria. The interaction of bacteria with the gas–liquid interface was shown to be a significant factor governing the drainage of the bacteria from the bioactive foam. Significance and Impact of the Study: Protein hydrolysate‐based bioactive foam may be a suitable treatment technology to enhance the biodegradation of petroleum hydrocarbons in soil.

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