AllyMax is a widely
used herbicide formulation in wheat-rice cropping
areas of the world. The residues of its active ingredients, tribenuron
methyl (TBM) and metsulfuron methyl (MET), persist in soil and water
as co-contaminants, and cause serious threats to nontarget organisms.
This study was performed to assess the potential of a bacterial consortium
for the degradation and detoxification of TBM and MET individually
and as co-contaminants. A bacterial consortium (B2R), comprising
Bacillus cereus
SU-1,
Bacillus velezensis
OS-2, and
Rhodococcus rhodochrous
AQ1, capable of degrading TBM and MET in liquid cultures was developed.
Biodegradation of TBM and MET was optimized using the Taguchi design
of experiment. Optimum degradation of both TBM and MET was obtained
at pH 7 and 37 °C. Regarding media composition, optimum degradation
of TBM and MET was obtained in minimal salt medium (MSM) supplemented
with glucose, and MSM without glucose, respectively. The consortium
simultaneously degraded TBM and MET (94.8 and 80.4%, respectively)
in cultures containing the formulation AllyMax, where TBM and MET
existed as co-contaminants at 2.5 mg/L each. Mass spectrometry analysis
confirmed that during biodegradation, TBM and MET were metabolized
into simpler compounds. Onion (
Allium cepa
) root inhibition and Comet assays revealed that the bacterial consortium
B2R detoxified TBM and MET separately and as co-contaminants. The
consortium B2R can potentially be used for the remediation of soil
and water co-contaminated with TBM and MET.
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