Abstract
The main organochlorinated compounds used on agricultural crops are often recalcitrant, affecting nontarget organisms and contaminating rivers or groundwater. Diuron (N-(3,4-dichlorophenyl)-N′,N′-dimethylurea) is a chlorinated herbicide widely used in sugarcane plantations. Here, we evaluated the ability of 13 basidiomycete strains of growing in a contaminated culture medium and degrading the xenobiotic. Dissipation rates in culture medium with initial 25 mg/L of diuron ranged from 7.3 to 96.8%, being Pluteus cubensis SXS 320 the most efficient strain, leaving no detectable residues after diuron metabolism. Pycnoporus sanguineus MCA 16 removed 56% of diuron after 40 days of cultivation, producing three metabolites more polar than parental herbicide, two of them identified as being DCPU and DCPMU. Despite of the strong inductive effect of diuron upon laccase synthesis and secretion, the application of crude enzymatic extracts of P. sanguineus did not catalyzed the breakdown of the herbicide in vitro, indicating that diuron biodegradation was not related to this oxidative enzyme.
Highlights
Worldwide ecosystems have received million tons of synthetic compounds, especially pesticides, since the development of chemical synthesis processes with agricultural and industrial purposes
The 13 basidiomycete strains evaluated here could not act upon diuron otherwise, since any of them could grow with the herbicide as the sole carbon and energy source (0 to 75 mg/L, 20 days—data not shown)
Diuron degradation ranged from 7.3% to 96.8%, being Pluteus cubensis SXS 320 the most active, followed by Hexagonia hirta MCA 131 (19.3%) and Pycnoporus sanguineus MCA16 (19.3%)
Summary
Worldwide ecosystems have received million tons of synthetic compounds, especially pesticides, since the development of chemical synthesis processes with agricultural and industrial purposes. Some basidiomycetes can be powerful tools for this purpose, because they produce enzymes, like laccases (Lac, EC 1.10.3.2), manganese-dependent peroxidases (MnP, EC 1.11.1.13), BioMed Research International and lignin peroxidases (LiP, EC 1.11.1.14); these enzymes have versatile catalytic mechanism, breaking down carbon linkages with aromatic ring fission, removing aryl-alkyl groups and lateral chains [6]. They can oxidize a wide range of phenolic and non-phenolic substrates, such as polycyclic aromatic hydrocarbons (PAHs) [7], dyes [8], pesticides [9], chlorophenols [10], and chlorolignin from residues of paper pulping [11]. We analyzed some aspects of the metabolism of tropical rainforest fungal strains with high capacity for diuron degradation, including possible relationships with ligninolytic enzyme production
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