Studies On The Application Of Metabolic Engineering To Degradation Of Hexachlorobenzene

Hexachlorobenzene (C6Cl6, HCB) was listed as one of the twelve persistent organic pollutants (POPs) in the Stockholm Convention for its tendency to accumulate along food chain and its recalcitrance to degradation, together with its harmful effects on human beings and environment. Microbial degradation is a promising effective approach to bioremediate environmental pollutants, including POPs. However, a pure culture capable of completely catabolizing HCB has not yet been isolated. Therefore, constructing an HCB-degrading strain via metabolic engineering may be a practical alternative to eliminate HCB in the environment.First, the possibility of degradation of hexachlorobenzene via co-culture was investigated.To convert Sphingobium chlorophenolicum ATCC 39723 to a hexachlorobenzene degrader by metabolic engineering,the gene cassette (camA+ camB+ camC) encoding a cytochrome P-450cam variant was integrated into non-essential gene pcpM of the pentachlorophenol degrader Sphingobium chlorophenolicum ATCC 39723 by homologous recombination (double crossover) under control of a tac-tac double tandem promoter. Although the recombinant failed to grow on hexachlobenzene as the sole carbon source, gas chromatography (GC) equipped with an electron capture detector (ECD) analysis showed that the recombinant strain could degrade 4.3μM HCB almost completely within 6 hours with...