Atrazine biodegradation by a monoculture of Raoultella planticola
isolated from a herbicides wastewater treatment facility
abstract
This research describes indigenous Raoultella planticola bacterial cells which were isolated from the
wastewater treatment plant of a herbicide factory. The optimum conditions for degrading atrazine were
at pH ¼ 7 and 28 C, with a degradation rate of 10 mg L1 h1
. Biodegradation was observed at temperatures
of 45 and 4 C and partial degradation was also observed at extreme pH values (3 and 10). The
degradation rates to reach 50% depletion of atrazine were 9.42, 7.42 and 5.42 mg L1 h1 in the presence
of acetonitrile, phenol or toluene, respectively. Successful inoculation of R. planticola into the original
sludge from the herbicide factory led to atrazine degradation within 3 h, instead of 3 days without the
inoculation. R. planticola developed a massive biofilm when exposed to atrazine. The results indicate that
the isolated R. planticola strain can be added to the arsenal of atrazine-degrading bacterial cells that have
the ability to degrade this substance under unfavorable conditions, such as those existing in the sludge of
herbicide factories. In addition, the isolated strain showed an ability to form a biofilm, which can be
utilized for improving the wastewater treatment.
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4. Conclusions
In this study, the isolated R. planticola showed high atrazine
degradation ability at pH 7 and 28 C. However, partial atrazine
degradation occurred even under extreme pH values such as 3 and
10. At extreme temperatures, such as 45 C, atrazine degradation
was even faster than at 28 C, but lasted only 3 cycles, and slow
degradation was observed even at 4 C. Atrazine degradation was
also observed in the presence of toxic organic solvents. Inoculation
of R. planticola into the original sludge from a herbicide factory
wastewater treatment facility showed good acclimation for atrazine
degradation which lasted the same period as in the MMA
experiments. Thus, enrichment of the indigenous bacterial cells in
wastewater treatment sludge with the isolated R. planticola may
lead to improve atrazine degradation and may reduce its risks to
the environment. The phenomenon of the isolated R. planticola
bacterial cells to grow on substratum as biofilm may enable the
development of a facility composed of particles covered with the
biofilm for maintaining atrazine bioremediation for a long period.
Ac