DDE Remediation and Degradation - Reviews of Environmental Contamination and Toxicology - page 59

III Aerobic Degradation and Remediation

The aerobic degradation pathway for DDT and DDE (Fig. 1), as presented by the
University of Minnesota Biocatalysis/Biodegradation Database (Ellis et al. 2006),
is one of several different pathways. Other variations have been suggested from
several sources (Quensen et al. 1998; Hay and Focht 1998; Nadeau et al. 1998).
The University of Minnesota Biocatalysis /Biodegradation Database (UMBBD)
proposed degradation pathway is not fully verified; thus, each boxed letter and
bracketed compound in Fig. 1 represent unknowns. To quote the UMBBD web-
site: “The steps labeled A, B, C, D, E are mutiple steps whose intermediates are
not identified yet. All descriptions as follows were proposed based on other simi-
lar experiments. In A , DDE is attacked by a dioxygenase at the ortho and meta
positions. Such an attack would give rise to a 2,3-dihydrodiol-DDE intermediate.
In B and D , 2-(4'-chlorophenyl)-3,3-dichloropropenoate may proceed via decar-
boxylation to yield 1,1-dichloro-(4'-chlorophenyl)ethane. The latter will undergo
oxidation of the aliphatic side chain to yield 1,1-dichloro-(4'-chlorophenyl)ethanol
which is further oxidized to yield 4-chloroacetophenone. The terminal ethyl
group of 1,1-dichloro-(4'-chlorophenyl)ethane may also undergo oxidation to
yield phenylacetic acid. In C , the transformation of 4-chloroacetophenone to
4-chlorobenzaldehyde may be via complete oxidation and subsequent decarboxy-
lation of the terminal methyl group. In E , the ring-cleavage product would be
further degraded to either a C-6- or C-5-chlorinated acid, depending on where the
hydrolytic cleavage takes place.”

Table 3 The five most effective microorganisms assessed in bioremediation studies and their
associated reductions in DDE

Percent reduction

Microorganism of DDE (time) Conditions Reference

Terrabacter sp. 38 (10 d) Soil-free aerobic Aislabie et al. 1999

(aerobic bacterium) liquid culture with

biphenyl

Phanerochaete 48 (18 d) Nitrogen-limited Bumpus et al. 1993

chrysoporium liquid culture

(fungus)

Pleurotus 78 (60 d) Sterile soil with Gong et al. 2006

plumonarius sawdust compost

(fungus)

Alcaligenes ~26 (14 d) Soil-free anaerobic Ahuja et al. 2001

denitrificans liquid culture

(facultative
bacterium)

Psuedomonas 42 (25 d) Soil-free aerobic liquid Hay and Focht 1998

acidovorans culture with biphenyl

(aerobic bacterium)