Aerobic dehalogenation

Figure 4 Reactions for aerobic dehalogenation ofhalocarbons by white-rot fungi.

Sharma PK, PL McCarty (1996) Isolation and characterization of a facultatively aerobic bacterium that reduc-tively dehalogenates tetrachloroethene to ciT-dichloroethene. Appl Environ Microbiol 62 761-765. 

Chlorobenzoates may be formed during the initial steps in the aerobic degradation of PCBs, and their further metabolism illustrates a number of pathways. There are several reactions that carry out dehalogenation including dioxygenation, hydrolysis, and reduction. 

Tetrachoroethylene (perchloroethylene, PCE) is the only chlorinated ethene that resists aerobic biodegradation. This compound can be dechlorinated to less- or nonchlorinated ethenes only under anaerobic conditions. This process, known as reductive dehalogenation, was initially thought to be a co-metabolic activity. Recently, however, it was shown that some bacteria species can use PCE as terminal electron acceptor in their basic metabolism i.e., they couple their growth with the reductive dechlorination of PCE.35 Reductive dehalogenation is a promising method for the remediation of PCE-contaminated sites, provided that the process is well controlled to prevent the buildup of even more toxic intermediates, such as the vinyl chloride, a proven carcinogen. 

Soil Under anaerobic conditions, pentachlorophenol may undergo sequential dehalogenation to produce /n-chlorophenol, tetra-, tri-, and dichlorophenols (Kobayashi and Rittman, 1982). In aerobic and anaerobic soils, pentachloroanisole was the major metabolite, with minor quantities of... 

Transformation and degradation of chlorinated compounds presumably via reductive dehalogenation and subsequent aerobic metaboAsm ... 

Much effort has been concentrated on the fate of chlorinated aliphatic hydrocarbons in aquifers (e.g., trichloroethylene, dichloroethylene). These chemicals undergo reductive dehalogenation under anaerobic conditions. By contrast, these compounds are degraded under aerobic conditions by methane-utilizing bacteria. For example, methan-otrophic bacteria can transform more than 50% of trichloroethane into CO2 and bacterial biomass. 

Table 3 Enzyme classes capable of transforming and dehalogenating organohalides under aerobic and...

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