Microbial degradation of chlorinated benzenes

Abstract

Chlorinated benzenes are important industrial intermediates and solvents. Their widespread use has resulted in broad distribution of these compounds in the environment. Chlorobenzenes (CBs) are subject to both aerobic and anaerobic metabolism. Under aerobic conditions, CBs with four or less chlorine groups are susceptible to oxidation by aerobic bacteria, including bacteria (Burkholderia, Pseudomonas, etc.) that grow on such compounds as the sole source of carbon and energy. Sound evidence for the mineralization of CBs has been provided based on stoichiometric release of chloride or mineralization of (14)C-labeled CBs to (14)CO(2). The degradative attack of CBs by these strains is initiated with dioxygenases eventually yielding chlorocatechols as intermediates in a pathway leading to CO(2) and chloride. Higher CBs are readily reductively dehalogenated to lower chlorinated benzenes in anaerobic environments. Halorespiring bacteria from the genus Dehalococcoides are implicated in this conversion. Lower chlorinated benzenes are less readily converted, and mono-chlorinated benzene is recalcitrant to biotransformation under anaerobic conditions.

Dechlorination and organohalide-respiring bacteria dynamics in sediment samples of the Yangtze Three Gorges Reservoir

“…There are several groups of bacteria which are able to dehalogenate chlorinated aliphatic and aromatic hydrocarbons under anaerobic conditions. Remarkably, similar groups of bacteria have been reported to be capable of dechlorination of CBs (Field and Sierra-Alvarez 2008;Taş et al 2011), PCBs (Bedard 2008), and chlorinated ethenes (Löffler et al 2000;Schmidt et al 2006). In this study, chloroethenes were used as model compounds.…”

Biodiversity of Dehalorespiring Bacteria with Special Emphasis on Polychlorinated Biphenyl/Dioxin Dechlorinators

“…However, while microbial reductive dehalogenation of haloaliphatic compounds has been studied extensively, less information is available on haloaromatic-dehalogenating microorganisms. There have in recent years been excellent review articles on the processes of microbial reductive dehalogenation of halo-aromatics 4,44,45,49,132) . The present review article focuses on up-to-date knowledge of the biodiversity of dehalorespiring bacteria and reductively dehalogenating microbial consortia with particular emphasis given to those capable of transforming polychlorinated biphenyls/dioxins (PBDs).…”

Compound-Specific Isotope Analysis (CSIA) Application for Source Apportionment and Natural Attenuation Assessment of Chlorinated Benzenes

“…As a consequence of their intense use as solvents, industrial intermediates, and pesticides (in the past, dichlorodiphenyltrichloroethane, DDT, was also produced from chlorinated aromatics), these compounds, and particularly chlorinated benzenes (CBs), are frequently encountered as soil and groundwater contaminants [3]. The characterization and remediation of contaminated sites involves high costs, estimated from 500 to 5 million euros on average per site (European Union (EU) data [1]); hence the application of the polluter pays principle (PPP) may become essential.…”

“…Conversely, lower CBs such as monochlorobenzene (MCB) preferentially degrade via oxidative processes to complete mineralization [21]. Anaerobic degradation such as reductive dehalogenation appears to be up to 10 times faster than aerobic oxidation processes [3]; however, it may have the disadvantage of generating benzene as a final product of the biodegradation, which in turn is more toxic than the starting products [22]. In contrast to compounds such as chlorinated ethenes, for which there is a well-developed literature on CSIA applications, only few studies are available for CBs.…”