Biodegradation of s-triazine herbicide: Atrazine by native soil bacterial isolates employing nanoparticles
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Date
2018-12
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
In present study a popular herbicide viz. atrazine degradation potential of two soil bacterial strains isolated from Crop research centre at G.B.P.U.A. & T., Pantnagar, Uttarakhand in year 2017 was investigated under optimized laboratory conditions. Based on cultural,morphological, biochemical and 16S rRNA gene sequencing, these bacterial isolates were identified as Bacillus badius ABP6 and Bacillus encimensis ABP8. All the isolates performed best at pH 7, 30ºC temperature and 150 rpm shaking speed. Supplementation of additional carbon and nitrogen sources in liquid medium enhanced degradation rate of atrazine by bacterial isolates. In an in vitro comparative biodegradation study conducted in minimal medium, soil slurry and soil microcosm, maximum degradation (84.80%, 86.40% and 87.70%) of atrazine was observed in treatment inoculated with bacterial consortium after 20 days. The atrazine degradation kinetics indicated that the degradation rate constant has ranged from 0.01 to 0.09 (minimal medium), 0.011 to 0.095 (soil slurry) and 0.012 to 0.138 (soil microcosm) for all the treatments. Immobilization of bacterial cells on sodium alginate beads, sugarcane baggase, nanozeolite and synthesized α-Fe2O3 nanoparticles showed maximum atrazine degradation in minimal medium, soil slurry and soil microcosm under consortium treatment, after 20 days as compare to free bacterial cells. SEM analysis revealed successful immobilization of bacterial cells on different immobilizing carriers. Rhizoremediation study conducted in maize (Zea mays) rhizosphere, further confirmed the siginificance of bacterial isolates in atrazine degradation. All bacterial treatments resulted in enhancement of maize growth response, chlorophyll and protein content, significantly over control. However carotenoid content was found to decrease in response to inoculation. Atrazine dissipation in soil and accumulation by Zea mays was observed in different time period and maximum accumulation was observed in roots while least was in leaves for all treatments. As compared to monoculture, consortium performed better in case of all the experiments conducted. HPLC, FTIR and GC-MS analysis confirmed the formation of metabolites as a result of biodegradation. Utilization of dynamic microorganisms is an efficient and economical strategy, while microbial immobilization gives a breakthrough in the restricted application of microbes in in-situ. The study clearly demonstrated that B. badius ABP6 and B. encimensis ABP8 were able to metabolize atrazine effectively and thus could be employed profitably for field scale bioremediation technology.
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