Enhancement and Biological Characteristics Related to Aerobic Biodegradation of Toluene with Co-Existence of Benzene

摘要

The interaction between different volatile organic compounds (VOCs) is a critical issue associated with bioremediation of co-contaminated sites. Contradictory results have been reported on the effects of coexistence of VOCs on biodegradation of each VOC. These contradictions are thought to be caused by inter-study variability in microbial diversity. To examine the effects of co-existing VOCs on biodegradation of each VOC, a series of biodegradation tests were carried out with a microcosm capable of degrading all three VOCs: dichloromethane (DCM), benzene, and toluene. We added different combinations of the VOCs to the microcosm while monitoring VOC concentration and microbial community diversity. Degradation of DCM and benzene was minimally influenced by co-existence of other VOCs; however, degradation of toluene was dramatically enhanced by the co-existence of benzene. Propioniferax was identified in cultures exposed to benzene alone and cultures simultaneously exposed to benzene, toluene, and DCM. Propioniferax was dominant, but prior to this study, it was not known to degrade benzene, toluene, and DCM. In the cultures exposed to only toluene, Rhodanobacter, Mycobacterium, Bradyrhizobium, and Intrasporangium increased during the biodegradation. The former three bacteria increased more rapidly when benzene and DCM were also included. These results suggest that co-existence of benzene and DCM can enhance the activity of Rhodanobacter, Mycobacterium, and Bradyrhizobium and consequently accelerate the degradation of toluene.