ENHANCEMENT OF BIODEGRADABILITY OF POLYCHLORINATED DIBENZO-p-DIOXINS

Abstract

Enhancement of biodegradability of polychlorinated dibenzo-p-dioxins (PCDDs) was studied with new isolated bacterial strains from soil and oxic-sediments contaminated by PCDDs. The results indicated that mono- and di-chlorinated dibenzo-p-dioxins could be utilized as a sole carbon source and degraded by isolated bacterial strains, but tri-chlorinated dibenzo-p-dioxin (TrCDD) was hardly degraded. The biodegradability of TrCDD and tetra-chlorinated dibenzo-p-dioxin (TCDD) by the strain Pseudomonas sp. EE41, a new isolated one, could be enhanced through primary nutrient of co-metabolism of o-dichlorobenzene (o-DCB). In this case, TrCDD (1.2 mg/l for 3 weeks) was degraded by 33.1% and the degradation rate enhanced more than 2 fold; also TCDD (0.1 mg/l for 3 weeks) biodegraded by 37.8%. Most highly chlorinated, Penta-, Hexa-, Hepta-, and Octa-chlorinated, dibenzo-p-dioxins (p-CDD, H₆₋, H₇-CDD and OCDD) tested in this study could not be degraded while accumulated in bacterial cells.

Keywords:

• Polychlorinated dibenzo-p-dioxins (PCDDs)
• Microbial degradation
• Co-metabolism
• Enhancement of biodegradability

ACKNOWLEDGMENTS

This work was supported by National Natural Sciences Foundation of China under contract No.29837180. We are grateful to Kangsheng Zhang in particular for improving the English.