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BIODEGRADATION OF DICHLORONITROBENZENES
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BIODEGRADATION OF DICHLORONITROBENZENES

Mallory Lynne Palatucci
University of West Florida
Master of Science (MS), University of West Florida
2017

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Abstract

Dichloronitrobenzenes (DCNB) are intermediates in the production of dichloroanilines, which are key feedstocks for synthesis of diuron and other herbicides. Despite the fact that it is a major contaminant at certain chemical manufacturing sites, there are no reports of DCNB biodegradation. Therefore, such sites are not candidates for bioremediation. Selective enrichment with samples from a contaminated site in Brazil led to the isolation of bacteria able to mineralize either 2,3-dichloronitrobenzene (2,3-DCNB) or 3,4-dichloronitrobenzene (3,4-DCNB). Both isolates released nitrite during growth on the respective DCNB isomers under aerobic conditions. The genome sequence of Acidovorax sp. JS3050 grown on 3,4-DCNB revealed the presence of putative nitroarene dioxygenase genes, which would be consistent with initial attack by a dioxygenase analogous to the initial steps in degradation of nitrobenzene and dinitrotoluenes. When enrichments from the contaminated site were used as inoculum in a fluidized bed bioreactor (FBR), 3,4-DCNB, 2,3-DCNB, 1,2-dichlorobenzene (o-DCB), and chlorobenzene (CB) were biodegraded simultaneously. Biodegradation of the mixtures was complete even when the reactor was operated at high flow rates and bacteria with the ability to degrade each of the contaminants were readily isolated from the reactor. The results indicate clearly that DCNB isomers are candidates for natural attenuation/bioremediation.
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