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Applied and Environmental Microbiology, June 2001, p. 2404-2409, Vol. 67, No. 6
INRS-Institut Armand-Frappier,
Université du Québec, Laval, Québec, Canada H7V 1B7
Received 29 November 2000/Accepted 16 March 2001
Enterobacter cloacae strain EM was isolated from a
commercial dietary mineral supplement stabilized by a mixture of
methylparaben and propylparaben. It harbored a high-molecular-weight
plasmid and was resistant to high concentrations of parabens. Strain EM was able to grow in liquid media containing similar amounts of parabens
as found in the mineral supplement (1,700 and 180 mg of methyl and
propylparaben, respectively, per liter or 11.2 and 1.0 mM) and in very
high concentrations of methylparaben (3,000 mg liter
0099-2240/01/$04.00+0 DOI: 10.1128/AEM.67.6.2404-2409.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Hydrolysis of 4-Hydroxybenzoic Acid Esters
(Parabens) and Their Aerobic Transformation into Phenol by the
Resistant Enterobacter cloacae Strain EM
1, or
19.7 mM). This strain was able to hydrolyze approximately 500 mg of
methyl-, ethyl-, or propylparaben liter
1 (3 mM) in less
than 2 h in liquid culture, and the supernatant of a sonicated
culture, after a 30-fold dilution, was able to hydrolyze 1,000 mg of
methylparaben liter
1 (6.6 mM) in 15 min. The first step
of paraben degradation was the hydrolysis of the ester bond to produce
4-hydroxybenzoic acid, followed by a decarboxylation step to produce
phenol under aerobic conditions. The transformation of 4-hydroxybenzoic
acid into phenol was stoichiometric. The conversion of approximately
500 mg of parabens liter
1 (3 mM) to phenol in liquid
culture was completed within 5 h without significant hindrance to
the growth of strain EM, while higher concentrations of parabens
partially inhibited its growth.
*
Corresponding author. Mailing address: INRS-Institut
Armand-Frappier, 531 boul. des Prairies, Laval, Québec, Canada,
H7V 1B7. Phone: (514) 687-5010. Fax: (514) 686-5501. E-mail:
francois_lepine{at}inrs-iaf.uquebec.ca.
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