Towards a hexachlorobenzene bioreactor
Hexachlorobenzene (HCB) is highly persistent environmental pollutant due to its chemical stability. It has been used in the production of rubber, as wood preserving agent and as pesticide and it is considered a possible human carcinogen. HCB is particularly relevant in Australia, since it holds the largest HCB stockpile in the world (Botany Bay Industrial Park, NSW). So far only physic-chemical technologies have been applied for the destruction of HCB; however, these methods do not ensure full destruction and may lead to the generation of more harmful compounds, such as dioxins. On the other hand, it is well known that obligate anaerobic bacteria are able to reductively dechlorinate HCB to less chlorinated congeners. Therefore, a biological approach seems to be a more suitable and environmental friendly solution.
In this study we present a microbial community, taken from a site contaminated with chlorinated solvents, capable of reductively dechlorinating HCB and 1,2,4,5- Tetrachlorobenzene (TeCB). Cultures were established using acetate and H2 or lactate as carbon source and electron donor, respectively. 1,3- and 1,4- dichlorobenzenes were the main breakdown products in the cultures supplied with 1, 2, 4, 5- TeCB, monochlorobenzene was also observed in a lower extent. Cultures with HCB only showed 1, 3, 5-Trichlorobenzene as breakdown product. Quantitative PCR, targeting Dehalococcoides´ 16S (a well-known dechlorinating bacterium) showed high abundance of this species in the cultures.