Aug. 2, 2012
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Bioremediation Consulting Inc., Watertown MA announced the completion of a research project funded by a Small Business Innovation Research (SBIR) grant from the National Science Foundation to develop a bacterial culture that biodegrades Polychlorinated Biphenyls (PCBs). Under the lead of its senior scientist, Dr. Margaret Findlay, a team of microbiologists at Bioremediation Consulting succeeded in developing a PCB-degrading bacterial culture which extensively dechlorinated Aroclor 1260 and 1254, two persistent PCB mixtures, in 18 weeks. BCI submitted its final report on June 12th showing the successful results of this project.
BCI presented its research findings on dechlorination of PCBs at the Battelle Conference - 'Remediation of Chlorinated and Recalcitrant Compounds', on May 23, 2012 in Monterey, California. The topic of BCI's research was 'PCB Biodegradation by a Dehalococcoides (Dhc) Culture Grown on Trichlorobenzenes'
PCBs are toxic pollutants that pose a threat to the health of ecosystems and to humans. BCI's product is the first and only commercially available culture of PCB-degrading bacteria. This proprietary accomplishment is remarkable in that historically other scientists have not succeeded in culturing PCB-degrading bacteria from environmental samples. It also has the potential to allow thousands of cubic yards of stockpiled PCB-contaminated sediments to be cost-effectively biologically treated.
Historically, scientists have observed only very slow degradation of PCBs in anoxic river sediments. The persistence of PCBs in the environment is likely explained by the low solubility of these contaminants, resulting in slow growth of the PCB-degrading bacteria. The dream of researchers has been to 'capture' these bacteria, grow them in water culture, and then apply large numbers of the bacteria to the contaminated soil.
In the past, failure of researchers to 'capture' these bacteria has been due to the bacteria's strong attachment to sediments. BCI, however, has developed a way to obtain water-borne PCB-degrading bacteria and has cultured them in an anoxic water medium by growing them with a water-soluble 'food'. BCI scientists selected trichlorobenzene (TCB), similar in structure to PCBs but 1000 times more soluble, as a PCB surrogate to support the bacteria's energy metabolism. After many cycles of growth on TCBs, the chlorinated benzenes were removed, and the culture was used to treat different PCB mixtures.
The PCB-degrading bacteria in the BCI culture are anaerobes, members of the Dehalococcoides genus. This genus also contains the dechlorinating bacteria which dechlorinate toxic chlorinated solvents, such as TCE (trichloroethene), by the enzymatic process of anaerobic reductive dechlorination, in which hydrogen atoms are substituted for chlorine atoms. The biodegradation of PCBs (two-ring aromatic compounds containing up to 10 chlorine atoms) by Dehalococcoides also involves substitution of hydrogen atoms for chlorine atoms.
BCIs culture was tested for its ability to degrade Aroclor 1260, a commercial PCB mixture of about 60 similar PCBs containing mainly 6 to 8 chlorines per molecule. Within 18 weeks, 44% of the 6, 7, and 8 chloro- PCBs were converted to new PCBs that had only 4, 5, or 6 chlorines. The culture also degraded Aroclor 1254, a commercial mixture of PCBs containing mainly 4 to 6 chlorines per molecule. Within 10 weeks, 33 % of these chlorines were removed with the formation of PCBs containing mainly 3 and 4 chlorines per molecule.