Construction of bioreactors for the degradation of volatile organic chlorinated solvents

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Tetrachloroethylene (or perchloroethylene, PCE) and trtichloerothylene (TCE) are known to be serious environmental pollutants in many countries. The present research aimed to develop strains which are able to degrade PCE and TCE efficiently, and construct bioreactors. Since PCE is not able to be degraded by aerobic bacteria, we attempted to isolate anaerobic bacteria and succesfully isolated strain Y51 which showed efficient dechlorination from PCE to cis-1,2-dichloroetnylene (DCE) via TCE.Y51 could grow up to 0.4 at O.D.660 nm in a minimum medium supplemented with 0,2% yeast extract, 50 mM sodium pyruvate and 5 mM fumarate, and dechlorinated PCE completely to DCE at a concentration of as high as 100 ppm. We have also constructed a hybrid dioxygenase from toluene dioxygenase and biphenyl dioxygenase, which showed tremendous degradation capability for TCE and DCE.We demonstrated total degradation of PCE by combining anaerobic Y51 and aerobic Pseudomonas strain D3 expressing the hybrid dioxygenase. The strain D3 could grow well to 1.2*10^9/ml in a glass colmn packed with sand, and degraded TCE (10 ppm) in 5 h. Anaerobic bioreactor using strain Y51, however, remained to be constructed.