Biochemical activities of 1,2-dichloroethane (DCA) degrading bacteria
One of the most widely produced industrial solvents is 1,2-dichloroethane (DCA), a known carcinogen, toxic to both terrestrial and aquatic ecosystems. Annual production in the United States, Japan and Europe alone are in excess of thirteen thousand metric tons. Entry into the environment is mainly due to poor handling, accidental spillages and illegal dumping. Five indigenous DCA degrading bacterial isolates capable of completely degrading DCA under aerobic conditions recently isolated from South African waste water treatment facilities, were found to belong to the genus Ancylobacter. The specific activities of the enzymes in DCA catabolism were compared with previously characterized DCA degrading bacterial isolates using crude cell lysates and different intermediates within the catabolic route as substrates. The catabolic route by which DCA is degraded was found to be similar to previously characterized isolates of Ancylobacter as well as Xanthobacter autotrophicus GJ10. The specific activities of all the enzymes within the catabolic route of the South African isolates were found to be lower when compared with previously characterized isolates. Polyacrylamide gel electrophoresis of crude cell lysates did not indicate over-expression of the hydrolytic dehalogenase as observed in a previously characterized isolate of Ancylobacter. Although, the overall specific activities of each of the enzymes in the DCA catabolic route were found to be lower in this study, these isolates may still have potential use in the bioremediation of DCA contaminated sites in South Africa.
Key words: 1,2- Dichloroethane, halogenated hydrocarbon, dehalogenase.