|495-1||Diuron degradation and N-demethylated metabolites production by Ganoderma lucidum|
|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) |
Herbicides are among the most important pollutants used in crops worldwide. Diuron is a phenylurea herbicide used mainly in sugar-cane cultivation in Brazil. The slow degradation of pesticides can lead to environmental contamination of water, soil and humans. White-rot fungi are Basidiomycetes with a great potential to degrade highly pollutant molecules, such as pesticides and this characteristic has been attributed to the action of intracellular (as cytochrome P450) and extracellular (as laccases) enzymes. Laccase production and diuron degradation by the white-rot fungi Ganoderma lucidum were studied in liquid stationary cultures using two medium types: 1) with glucose at 1% as the sole carbon source and 2) using a corn corb extract at 3% to stimulate ligninolytic enzyme production. All the media types contained diuron (30 μM) at the beginning of the cultivation. Control cultures were performed without diuron. The diuron degradation was evaluated by HPLC. Laccase production was significantly enhanced in corn cob cultures (1,370 U/L ±426 in corn cob medium and 670 ±20.3 U/L in glucose medium, p≤0.05). The presence of diuron slightly inhibited the laccase production and had no effect on mycelial growth compared with the controls. Corn cob cultures were more efficient in diuron degradation (46%) than glucose cultures (22%) after 25 days. The degradation was accompanied by the appearance of N-demethylated metabolites in the filtrate of both corn cob and glucose cultures. On day 5 it was possible to detect the appearance of the first N-demethylated metabolite DCPMU [1-(3,4-Dichlorophenyl)-3-methylurea] and the second metabolite DCPU [(3,4-Dichlorophenyl)urea] was detected in a smaller concentration on day 15. During the first 15 days, the production of these metabolites from diuron in corn cob cultures was faster than in glucose cultures, suggesting the participation of laccases in the degradation process. For example, in corn cob cultures 0.5 and 1.02μg/ml of DCPMU were produced on 5 and 15 day, respectively. In contrast, in glucose cultures 0.18 and 0.5μg/ml of DCPMU were detected at the same times. Both degradation products remained in the culture filtrates until the end of the experiments. These results show that G. lucidum is able to degrade the diuron molecule by a demethylation process and has the potential to be applied to diuron contaminated environments.
Palavras-chave: diuron, ganoderma lucidum, herbicida, lacases