Trichloroethylene (TCE) and phenol were often found together as co-contaminants in the groundwater of industrial contaminated sites. An effective method to remove TCE was aerobic biodegradation by co-metabolism using phenol as growth substrates. However, the aerobic biodegradation process was easily limited by low concentration of dissolved oxygen (DO) in groundwater, and DO was improved by air blast technique with difficulty. This study enriched a bacterial community using hydrogen peroxide (H2O2) as the sole oxygen source to aerobically degrade TCE by co-metabolism with phenol in groundwater. The enriched cultures were acclimatized to 2-8mM H2O2 which induced catalase, superoxide dismutase and peroxidase to decompose H2O2 to release O2 and reduce the toxicity. The bacterial community could degrade 120mg/L TCE within 12 days by using 8mM H2O2 as the optimum concentration, and the TCE degradation efficiency reached up to 80.6%. 16S rRNA gene cloning and sequencing showed that Bordetella, Stenotrophomonas sp., Sinorhizobium sp., Variovorax sp. and Sphingobium sp. were the dominant species in the enrichments, which were clustered in three phyla: Alphaproteobacteria, Betaproteobacteria and Gammaproteobacteria. Polymerase chain reaction detection proved that phenol hydroxylase (Lph) gene was involved in the co-metabolic degradation of phenol and TCE, which indicated that hydroxylase might catalyse the epoxidation of TCE to form the unstable molecule TCE-epoxide. The findings are significant for understanding the mechanism of biodegradation of TCE and phenol co-contamination and helpful for the potential applications of an aerobic bioremediation in situ the contaminated sites.
Bibliographical noteFunding Information:
This work was supported jointly by National Natural Science Foundation of China (51378208, 41273109, 41003031), Specialized Research Fund for the Doctoral Program of Higher Education (20110074130002), Shanghai Rising-Star Program (12QA1400800), Fok Ying Tung Education Foundation (141077), Program for New Century Excellent Talents in University (NCET-13-0797), Innovation Program of Shanghai Municipal Education Commission (14ZZ059), Fundamental Research Funds for the Central Universities (222201313008). We also would like to thank the anonymous referees for their helpful comments on this paper.
- aerobic biodegradation
- bacterial community
- chlorinated hydrocarbon
- hydrogen peroxide