Biodegradation of phenylurea herbicides by a novel degrading microbial consortium

Abstract

In the last decades, ecofriendly methods have emerged for remove contaminated environments using different microbial species. Bioremediation has demonstrated to be an efficient tool to decontaminate pesticides polluted sites in environment. Phenylureas herbicides attenuation in the environment is primarily achieved through microbial degradation processes. In this work, a novel phenylurea degrading bacterial consortium composed of three degrading strains, including; Arthrobacter sulfonivorans N2 purchased from the Institut Pasteur Collection, Variovorax soli SRS16, kindly provided by the Dr. Sebastian R. Sorensen from Geological Survey of Denmark and Greenland (GEUS) [1] and Advenella sp. JRO, isolated in our laboratory from a highly contaminated industrial site with polycyclic aromatic hydrocarbons (PAHs) [2], has been inoculated to enhance biodegradation. The application of microbial consortia improve the efficiency of biodegradation because the metabolic intermediate of one bacterium can be utilized by another as source carbon, thus accelerating biodegradation and avoiding potential toxic effects of the metabolites formed [3]. Enhanced degradation of phenylurea herbicides has encouraged research to isolate and characterize degrading bacteria from adapted soils. Studies emphasizing the importance of bacterial consortia with strains providing synergistic catabolic cooperation for the biodegradation of phenylurea herbicides have been lately reported [4]. Biodegradation of a given molecule could involve many types of microorganisms. This situation which is commonly found in environment and explains, at least partly, why biodegradation of many herbicides and others pollutants occurs in the presence of a consortium of microorganisms. When phenylurea herbicides biodegradation assays were conducted employing three degrader strains simultaneously (microbial degrading consortium, MDC), Arthrobacter sulfonivorans, Variovorax soli and Advenella sp. JRO, a high percentage of biodegradation could be observed in all cases (Table 1). All biodegradation curves fitted to a Hockey Stick kinetic model, except in the case of isoproturon, which was fitted to a single first order kinetic model. Fluometuron, chlorotoluron, linuron, diuron were capable to degrade 63.1%, 71.5%, 79.2% and 80.2% and the DT50 observed 2, 1, 15, 1 days, respectively. The most relevant result was obtained when the MDC was inoculated to biodegrade isoproturon, achieving an extent of isoproturon biodegradation of 99.2% and DT50 9 days.

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