Phytodegradation of p,p '-DDT and the enantiomers of o,p '-DDT

The reductive dechlorination of p,p'- and o,p'-DDT at the mu g/mL level in the presence of the aquatic plant Elodea (Elodea canadensis) and the terres trial plant kudzu (Pueraria thunbergiana) is described; studies included an alysis of the enantiomers of chiral o,p'-DDT and its chiral degradation pro duct, o,p'-DDD, to determine whether the reaction was enantioselective. The degradation process was followed by GC using a gamma-cyclodextrin-based ch iral phase. The half-lives for degradation of both o,p'- and p,p'-DDT by El odea and kudzu ranged from 1 to 3 days, apparently depending on growth cond itions of the plants. The only products identified were o,p'- and p,p'-DDD; no DDE or DDA were detected. Phytodegradation experiments using Elodea and carbon-14 labeled p,p'-DDT indicated that up to 22% of DDT analogues were covalently bound within the plant. DDT degradation by Elodea was only about 40% slower after gamma irradiation at 300 krads, indicating the major proc ess not to be dependent upon live microbes. Dead Elodea was shown to mainta in reductive activity at about the same rate as fresh plants. The reactions with Elodea and kudzu were not enantioselective in the formation of o,p'-D DD from o,p'-DDT. Reductive dehalogenation of o,p'-DDT by a partially purif ied extract of Elodea, by the porphyrin hematin, and by human hemoglobin wa s also shown to be nonenantioselective, with reaction rates similar to that for the whole plant. This evidence suggests that the phytodegradation proc ess may be catalyzed by an achiral enzyme cofactor or other achiral biomole cule.