الفهرس 
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Abstract
A field survey was conducted in El Sharkia and Port Said to collect
soil samples from previously herbicides sprayed soils. Soil samples were
investigated on herbicides containing media to isolate bacterial strains
capable of degrading herbicides and utilized them as carbon and nitrogen
source. About 65 bacterial strains were isolated on clodinafop-propargyl
(CF) and tribenuron-methyl (TBM) containing media.
Only, two bacterial strains named HT31 and HT44 and identified
as Bacillus sp. and Bacillus cereus, respectively, utilize clodinafoppropargyl
as a carbon source and nitrogen source and degraded 88.7%
and 87.5%, respectively, of 80 mg/L CF within 12 h.
With the degradation process the bacterial biomass and the
chloride ion were increased with the time. The bacterial strain HT31 was
higher than the strain HT44 in growth biomass and also in release of
chloride ion as a result to clodinafop-propargyl biodegradation.
In the same time four bacterial strains were named HT9, HT12,
HT16 and HT25 identified, respectively, as Acinetobacter lwoffii,
Bacillus thuringiensis, Lysinibacillus sp. and Bacillus sp. Those bacterial
isolates utilize tribenuron-methyl when grown on glucose mineral salt
medium and degraded 87.8, 85.4, 81.4 and 79.2%, respectively, of initial
50 mg/L TBM within 12 h.
The degradation of clodinafop-propargyl and tribenuron-methyl
was investigated by HPLC. Whereas, the clodinafop propargyl did not
appear in HPLC chromatogram of inoculated media as compared to control (uninoculated media), while the metabolite of clodinafop
propargyl appear.
The growth of bacterial strain increased with time and the
concentrations of herbicides clodinafop-propargyl and tribenuron-methyl
decreased. In the same time, the derivatives of herbicides increased with
the time. The growth conditions for bacterial isolates indicated that the
degradation of herbicides depend on initial herbicide concentration and
increasing the herbicide concentration decreased the degradation process.
The results indicated that glucose, glycerol and sucrose were the
best carbon source for TBM degradation and also NH4Cl was the best
nitrogen source for the degradation of TBM.
from the results the optimum temperature for the growth of
selected isolates to degrade CF and TBM, were between 30 and 35ºC for
all strains. Also, the optimum pH for all strains to degrade CF or TBM
were between 7 and 8.
The selected strains in this study exhibited esterase activities after
12 and 24 hours of incubation in media supplemented with 80 mg/L CF
or 50 mg/L TBM. However the esterase activities at 24 hr were less than
at 12 hr and this decrease was insignificant with all bacterial strains.
The results of this study indicated that those isolated bacterial
strains will be subjected to further studies to be used in bioremediation of
herbicides residues in contaminated soils to overcome the pollution
problem.