|495-3||Degradation of the herbicide diuron by Phanerochaete chrysosporium|
|Autores:||Jaqueline da Silva Coelho-moreira (UEM - Universidade Estadual de Maringá) ; Caroline Aparecida Vaz de Araújo (UEM - Universidade Estadual de Maringá) ; Cristina Giatti Marques de Souza (UEM - Universidade Estadual de Maringá) ; Adelar Bracht (UEM - Universidade Estadual de Maringá) ; Rosane Marina Peralta (UEM - Universidade Estadual de Maringá) |
Diuron is a persistent phenylurea herbicide widely used to control broad-leaf weeds mainly in sugar-cane cultivation. In soil, diuron has a half-life of 90-180 days being able to contaminate water and groundwater. The most studied white-rot fungi, Phanerochaete chrysosporium, has been shown a great ability to degrade diverse group of pollutants, including pesticides. This characteristic has been attributed to the action of intracellular (cytochrome P450) and extracellular (peroxidases) enzymes. In this work we report the rapid degradation of diuron by P. chrysosporium as well as the main metabolites formed from the herbicide. An attempt was also done to correlate the production of ligninolytic enzymes (lignin peroxidase (LiP), and Mn peroxidase (MnP), with the capability of fungus to degrade diuron. The degradation experiments were performed in stationary liquid medium at 28ºC in the dark. The fungus was inoculated in liquid medium containing corn cob extract, mineral solution, 1% glucose and 1.2 mM ammonium tartrate with or without 30 μM diuron. The mycelia were collected to determine the dry weight and to extract diuron possibly adsorbed or uptaken by the cells. The presence of diuron in the cultures significantly increased the lignin peroxidase activity (88 U/L) but had no effect on MnP activity (26.4 U/L) when compared to the control cultures (47 U/L and 22.4 U/L, to LiP and MnP, respectively). The dry biomass reached 136.3 mg at the 10 day of cultivation and was not changed by the presence of diuron. Diuron was almost completely removed within 10 days, which was accompanied by a sharp biomass and ligninolytic enzymes enhance. In addition, the removal of diuron was also accompanied by the formation of metabolites, which were detected by HPLC. The concentration of DCPMU [1-(3,4-Dichlorophenyl)-3-methylurea] reached 0.74 μg/ml on day 5 and decreased to 0.08 μg/ml at the end of the experiment. Just traces of the metabolite DCPU [(3,4-Dichlorophenyl)urea] were observed not exceeding 0.06 μg/ml and no 3,4-DCA (3,4-Dichloroaniline) production was detected. A content of 13, 23.2 and 25% of diuron, DCPMU and DCPU were founded on mycelial extracts, respectively. These data suggest the participation of an intracellular enzymatic system, probably the fungal cytochrome P450, in degradation of diuron by P. chrysosporium.
Palavras-chave: herbicide, Phanerochaete chrysosporium, lignin peroxidase, manganese peroxidase