Cometabolic degradation of dichloroethenes by Comamonas testosteroni RF2.

An environmental isolate Comamonas testosteroni strain RF2, which has been found to cometabolize trichloroethene (TCE) in the presence of phenol and sodium lactate as growth substrates, was tested to investigate its capacity for degrading 1,2-cis-dichloroethene (cDCE), 1,2-trans-dichlorothene (tDCE), and 1,1-dichloroethene (1,1DCE). Degradation assays were performed for single DCEs, as well as for a mixture of DCEs with TCE, which resembled contaminated plume in groundwater. RF2 was capable of efficiently removing all three dichloroethenes (DCEs) at the initial aqueous concentrations of 6.01 mg L-1 for cDCE, 3.80 mg L-1 for tDCE and 0.65 mg L-1 for 1,1DCE, with a removal efficiency of 100% for cDCE, 65.8% for tDCE, and 46.8% for 1,1DCE. Furthermore, complete removal of TCE, cDCE and 1,1DCE (122.5 μg L-1, 84.3 μg L-1 and 51.4 μg L-1, respectively) was observed in a mixture sample that also contained 72.33 μg L-1 of tDCE, which was removed to the amount of 72.3%. Moreover, degradation of cDCE (6.01 mg L-1) led to a 93.8% release of inorganic chloride, and 2,2-dichloroacetaldehyde was determined as the first intermediate of cDCE transformation. The findings of this study suggest that the strain RF2 exhibits the potential to remediate groundwater contaminated with less chlorinated ethenes.