Microbial Transformation of Phthalate Esters: Diversity of Hydrolytic Esterases - Environmental Contamination: Health Risks and Ecological Restoration - page 332

COOCH 3

COOCH 3

COOCH 3

COOH

(I) (II)

COOH

COOH

Meta- cleavage

OH

COOH

OH

(III)

(IV)

FIGURE 15.5
The. pathway. of. DMTP. biodegradation. by. A. niger .. (I). dimethyl. terephthalate;. (II). mono-
methyl.terephthalate;.(III).terephthalic.acid;.and.(IV).protocatechuate..(From.Ganji,.S.H..et.al.,.
Biodegradation ,.6,.61,.1995.)

3-carboxymuconate. cycloisomerase,. 4-carboxymuconolactone. decarboxyl-
ase,.and.β-ketoadipate.enol-lactone.hydrolase.in. Pseudomonas putida .
For. the. nonluorescent. strain. P. testosteroni ,. protocatechuate. was. trans-
formed. by. meta -cleavage. by. protocatechuate. 4,5-dioxygenase. to. yield.
intermediate. 2-hydroxy-4-carboxymuconic. semialdehyde. as. a. product. of.
the. ring. cleavage.. The. 2-hydroxy-4-carboxymuconic. semialdehyde. was.
oxidized. to. form. three. carboxyl. groups. (Keyser. et. al.. 1976).. The. process.
was. explained. in. detail. in. other. articles,. for. different. species. of. bacteria.
utilizing.protocatechuate.(Eaton.2001).(Figure.15.5)..In.these.further.oxida-
tions,.4-oxalomesaconate.was.produced.by.enzymes.and.then.transformed.
to.pyruvate.
Although. most. of. the. evidence. gathered. indicated. that. P. luorescens . can.
utilize.DMP. as. the.sole. carbon. and. energy.source,. there.is.one. report. that.
showed. contradictory. results. (Chauret. et. al.. 1995).. It. was. found. that. this.
strain.indeed.transformed.di- n -butyl.phthalate.(DBP).to.phthalate;.however,.
no.degradation.of.substrate.PA.was.observed,.whereas.the.fragment.of.buta-
nol.was.utilized.as.the.sole.carbon.source..The.most.interesting.part.of.the.
report.was.that.the.addition.of.respiration.inhibitor,.sodium.azide,.and.a.cat-
ionic.agent,.polymyxin.B,.increased.the.permeability.of.the.outer.membrane.
of. cells.. As. a.result,. the. organic. chemical. entered. into. the. cell.more. easily,.
resulting.in.a.sharp.increase.of.the.primary.degradation.
Meanwhile. P. luorescens . was. demonstrated. to. degrade. terephthalic.
acid. (TA). (Karpagam. and. Lalithakumari. 1999).. According. to. the. report,.