Development of hexachlorobenzene-dechlorinating mixed cultures using polysorbate surfactants as a carbon source.

The use of three nonionic polysorbate surfactants--Tween 60, 61 or 65--as the sole carbon source to sustain methanogenesis and dechlorination, as well as the effect of long-term exposure of enriched cultures to these surfactants, was investigated through the development of three sediment-derived cultures. Over a one-year period, the carbon source in these cultures was gradually switched from glucose and methanol to surfactant only, while the surfactant concentration was increased from an initial concentration of 100 mg/L to 400 mg/L. In each feeding cycle, the surfactants were partially degraded and converted to methane. Transition from glucose to Tween surfactants as the electron donor did not affect the rate, extent, and pathway of HCB transformation. These surfactants sustained the reductive dechlorination of HCB even after one year of continuous addition to the enriched cultures. This study demonstrated that reductive dechlorination of HCB sustained by the fermentation of Tween surfactants is feasible. The results support the use of anaerobically degradable Tween surfactants for the biotransformation of polychlorinated organic compounds. In principle, these surfactants could be used to simultaneously increase the bioavailability of subsurface contaminants while serving as the carbon and electron source for microbial reductive dechlorination.