Glucose-induced biodegradation of cis-dichloroethylene under aerobic conditions

The capability of the simple carbohydrate, glucose, to stimulate aerobic biodegradation of cis-dichloroethylene (cis-DCE) was tested using a river sediment. Greater reductions in cis-DCE were observed in aerobic microcosms incubated with glucose than in either killed controls, bottles incubated with oxygen and no glucose, or bottles containing glucose and no oxygen. Two aquifer sediments from different geographic locations also showed similar trends in dichloroethylene reduction. A sediment-free transfer culture from the original river sediment was further tested for cis-DCE degradation. Results indicate that cis-DCE losses coincide with an increase in chloride-ion concentration. The increase was equivalent to the amount of chloride that would be expected from the measured reduction in dichloroethylene and the release of two chlorides per cis-DCE. The possibility that methanotrophic or ammonia-oxidizing bacteria mediated dichloroethylene destruction was eliminated, because the sediment-free suspension culture showed no evidence of either activity. Hence, it appears that a new type of activity mediated the observed dichloroethylene transformation. The implications of these results on in situ bioremediation of chloroethylenes are discussed.