Biodegradation of phthalate esters using efficient microorganisms
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Date
2019
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DIVISION OF MICROBIOLOGY ICAR- INDIAN AGRICULTURAL RESEARCH INSTITUTE, NEW DELHI
Abstract
The present study was carried out for isolation, identification and characterization of
DEP and DEHP degrading bacteria from Centre for Cultivated Protection
Technology (CPCT) IARI, New Delhi. Phthalate esters are categorized according to
their molecular weight. DEHP is classified as higher molecular weight esters while
DEP as low molecular weight. Both the PAEs are well-known xenobiotics and
recalcitrant nature. Phthalate esters and their metabolites are known to exhibit
carcinogenic action and also found to be endocrine disruptors and produce adverse
reproductive, neurological and immune effect in both human and wildlife.
In solving the serious problems of pollution caused by phthalate esters, it is
important to assess the potential of bacterial strains indigenous to sites, contaminated
with phthalate esters for their ability to degrade DEP and DEHP. The eleven
bacterial isolates were identified through 16S rDNA sequencing, which grew well at
500 ppm of DEP and DEHP as sole carbon source in minimal salt medium.
However, reduction in their growth was observed at 700 ppm both DEP and DEHP.
Out of eleven isolates, ten isolates belonged to class γ Proteobacteria, matched with
sequences of Pseudomonas and Enterobacter. One isolate Achromobacter belonged
to β- Proteobacteria. DEP degradation by Achromobacter xylosoxidans strain
DEPA3 is reported for the first time in the present study and these might represent
new DEP-degrading taxa.
HPLC studies revealed decrease in the residual DEP and DEHP and
formation of intermediates such as Phthalic acid by selected isolates. The three
isolates viz Pseudomonas sp. DEHPA2, Pseudomonas sp. DEHPB2 and
Pseudomonas sp. DEHPC2 were inoculated individually and also as consortium in
MS broth containing 300 mg L-1 DEHP as sole carbon source.
The most efficient degradation was observed when the three bacteria were
inoculated as consortium. The DEHP percentage degradation was observed 79.8 -
87.8% after 10 days, 87.1- 91.3% after 20 days and 88.7 to 96.6% after 30 days of
incubation in MS broth. Also, study in soil microcosm and the variation in
percentage DEHP degradation among the bacterial isolates from 72.2 to 88.5% from
10 days to 30 days of incubation but a good DEHP percentage degradation was
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observed with consortium of three bacteria. Three bacterial isolates namely viz.
Achromobacter xylosoxidans strain DEPA3, Pseudomonas plecoglossicida strain
DEPB3 and Enterobacter cloacae strain DEPC1 were selected for the degradation of
DEP in MS broth and soil microcosm in different time interval by individuals and
consortium of three bacteria. In MS broth (84.91 - 96.14%) observed more DEP
degradation than soil microcosm (81.16-92.39%). The potential isolates obtained in
the present study can be used for developing consortium which can be tested further
at larger scale to strengthen the findings of the study.
Description
T-10152
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