Environmental Engineering Reference
In-Depth Information
6.4 Accomplishments of the flask evaluation
6.4.1 Designing and testing PCB-growing GEMs
6.4.1.1 Characterization of aerobic PCB metabolism by
biphenyl-degrading organisms
Analysis of the dechlorination patterns in anaerobic sediments resulted in
identification of eight ortho- and ortho- + para-chlorinated PCB congeners,
which account for up to 80% of the total Aroclor 1242 products in anaerobi-
cally dechlorinated sediments and are primary targets for the aerobic phase
of the PCB bioremediation scheme. Correspondingly, we have concentrated
on studying aerobic metabolism of these eight PCB congeners, both individ-
ual and given as defined mixtures M and C (Figure 6.6).
We characterized PCB cometabolism by biphenyl-degrading gram-pos-
itive
Rhodococcus erythreus
NY05 and
Rhodococcus
sp. RHA1, and gram-neg-
ative
Comamonas testosteroni
VP44 and
Burkholderia xenovorans
LB400. Metab-
olism of PCBs by these strains has been studied in detail for the range of
substrates, rates of PCB oxidation, intermediates, dead-end products, and
specificity of biphenyl ring oxidation (summarized in Maltseva et al., 1999).
The 2-, 4-, and 2,4-CBs were easily degraded via preferential oxidation of
the nonchlorinated ring of these CBs. Incomplete transformation of 2-CB by
50
A: Aroclor 1242
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B: Pattern M
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ยท
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C: Pattern C
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0
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Peak Number
Figure 6.6
Pattern M and C profiles compared to Aroclor 1242. See Quensen et al.,
1990b for cogeners represented by each peak number.
