Environmental Engineering Reference
In-Depth Information
(a)
Zn
-
O
HO
HO
HO
HO
O
P
O
P
H
HO
X
Zn
HO
Zn
x = o
-
O
(b)
(c)
-
HO
H
x = s
S
Zn
HO
HO
HO
P
Zn
P
S
HO
HO
O
Zn
-
O
Zn
H
Zn
-
O
H
-
E
(e)
(d)
-
S
-
Zn
Zn
-
S
HO
-
-
HO
HO
O
P
O
Zn
H
P
P
O
O
HO
HO
HO
H
O
H
H
HO
HO
HO
Zn
Zn
O
Zn
H
FIGURE 6.5
(a-e)Laststepofthemechanismofactionof Flavobacterium sp.PTE.Phosphoricacidisobtainedastheinal
productofpesticidehydrolysis,andtheactivesiteof Flavobacterium sp.PTEisregenerated.TheE represents
any electrophilic species naturally occurring in the microambient. (From Ortiz-Hernández, M. L., Quintero-
Ramírez, R., Nava-Ocampo, A. A., and Bello-Ramírez, A. M., Study of the mechanism of Flavobacterium sp.
forhydrolyzingorganophosphatepesticides. Fundam. Clin. Pharmacol., 2003,17:717-723.CopyrightWiley-VCH
VerlagGmbH&Co.KGaA.Reproducedwithpermission.)
andthioformaldehydewerenotidentiied.Theirabsencemaybeduetoanumberoffac-
tors; however, it seems most likely that ethion and its degradation products were rap-
idly utilized for microbial growth (Foster et al. 2004). Factors inluencing the ability of
Pseudomonas putida strains (epI and epII) to degrade the organophosphate ethoprophos
were described (Karpouzas and Walker 2000). Degradation of ethoprophos was most
rapid when bacterial cultures were incubated at 25°C and 37°C. Pseudomonas putida epI
was capable of completely degrading ethoprophos at a slow rate at 5°C compared with
Pseudomonas putida epII,whichcouldnotcompletelydegradeethoprophosatthesamerate.
Degradationby Pseudomonas putida epIinamineral-saltmediumplusnitrogenwasaccom-
paniedbyconcurrentbacterialgrowth,suggestingthat Pseudomonas putida epIwasgrow-
ingattheexpenseofethoprophos(KarpouzasandWalker2000).Bothisolateswereableto
rapidlydegradeconcentrationsofethoprophosashighas50mg/l,whichis10timesthe
recommendedieldrate,inlessthan3days.Severalstudieshavepreviouslyreportedthe
isolation of microorganisms capable of rapid degradation of other pesticides at similar
concentrations (Parekh et al. 1994; Struthers et al. 1998). Another factor that, according
to Zaidi et al. (1988), can inluence the degradation activity of microorganisms capable
of degrading pesticides is the pH value. Ethoprophos-degrading isolates were capable
ofrapidlydegradingethoprophosintherangeof5.5-7.6.Similardatawereobtainedby
Mandelbaum et al. (1993), who reported that degradation of atrazine by a Pseudomonas
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