Toxicología ambiental y analítica

Biodegradation of DDE and DDT by Bacterial Strain Stenotrophomonas sp. DXZ9

Abstract

Hui Xie, Lusheng Zhu, Jun Wang, Jinhui Jiang and Jinhua Wang

Bacterial strain DXZ9, which is able to degrade DDE, was isolated from the sludge of a pesticide factory. The sludge had been contaminated with DDT during an enrichment culture technique. The bacteria was identified as a Stenotrophomonas sp. The effects of various factors, such as pH, temperature and the concentration of the initial substrate on the degradation portion of DDE were investigated. The results showed that the DDE biodegradation proportion was 39.4% at the end of the 5th day, and the biodegradation proportion increased slightly and reached 41.9% at the end of the 10th day. Optimally, the pH, the concentration of the substrate, and the cultivation temperature were 7, 10 mg/l and 30°C, respectively, within 5 days and based on experimental optimization. DDT, the parent compound of DDE, could also be degraded by this bacterium; the biodegradation proportion of DDT was 55.0% and 57.6% at the end of the 5th and 10th days, respectively. The metabolites were analyzed by gas chromatography/mass spectrometry (GC/MS). DDT is dehydrochlorinated to DDE by bacterium DXZ9, and the metabolites of DDE were multipler undefined substances. These results indicate that DXZ9 has the ability to metabolize DDE and its parent compound, and it shows tremendous potential for use in field applications for the bioremediation of contaminated soil.