REDUCTIVE DEHALOGENATION OF POLYCHLORINATED-BIPHENYLS BY ANAEROBIC MICROORGANISMS ENRICHED FROM DUTCH SEDIMENTS

The dehalogenation of PCBs by anaerobic microbial cultures enriched fr om Dutch sediments was investigated. One mixed culture originating fro m estuarine sediments of the River Rhine (the Chemie Harbour), dehalog enated 2,2',3,3',4,4'- and 2,2,',3,3',6,6'-hexachlorobiphenyls (HCB) t o yield penta- and tetrachlorobiphenyls, whereas no lower chlorinated biphenyls could be detected. Mainly ortho dehalogenated products were found, but meta and para dehalogenated products were also present. Ano ther anaerobic culture which had been enriched from River Rhine sedime nts with 2,3,6-trichlorobenzoate as selective substrate reductively de halogenated hexachlorobiphenyls without a lag-phase to give penta- tet ra- and trichlorobiphenyls. No dimono- or non-chlorinated biphenyls co uld be detected. Sulphidogenic conditions appeared to reduce the dehal ogenation rate. A mixture of the two enrichments described above dehal ogenated decachlorobiphenyl to give traces of nona-, hepta-, hexa-, pe nta-, tetra- and trichlorobiphenyls; with a hexachlorobiphenyl, tentiv ely identified as either 2,3,3',4,5,5'- or 2,3,3',4',5,5'-hexachlorobi phenyl, as major product. In contrast to other reports of anaerobic PC B dehalogenation, the presence of sediment was not necessary for dehal ogenation and low initial concentrations (+/- 1.5 mu M or 0.7 ppm) wer e dehalogenated. Copyright (C) 1996 Elsevier Science Ltd