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Degradation of the herbicide bentazon as related to enzyme production by Phanerochaete chrysosporium in two solid substrate fermentation systems
Authors:del Pilar Castillo  Maria  Ander  Paul  Stenström  John  Torstensson  Lennart
Affiliation:(1) Department of Microbiology, Swedish University of Agricultural Sciences, Box 7025, S-750 07 Uppsala, Sweden;(2) Department of Wood Science, Swedish University of Agricultural Sciences, Box 7008, S-750 07 Uppsala, Sweden
Abstract:
Enzyme production and degradation of the herbicide bentazon by Phanerochaete chrysosporium growing on straw (solid substrate fermentation, SSF) and the effect of nitrogen and the hydraulic retention time (HRT) were studied using a small bioreactor and batch cultures. The best degradation of bentazon was obtained in the low nitrogen treatments, indicating participation of the ligninolytic system of the fungus. The treatments that degraded bentazon also had manganese peroxidase (MnP) activity, which seemed to be necessary for degradation. Pure MnP (with Mn(II) and H2O2) did not oxidize bentazon. However, in the presence of MnP, Mn(II) and Tween 80, bentazon was slowly oxidized in a H2O2-independent reaction. Bentazon was a substrate of pure lignin peroxidase (LiP) and was oxidized significantly faster (22,000–29,000 times) as compared to the MnP-Tween 80 system. Although LiP was a better enzyme for bentazon oxidation in vitro, its role in the SSF systems remains unclear since it was detected only in treatments with high nitrogen and high HRT where no degradation of bentazon occurred. Inhibition of LiP activity may be due to phenols and extractives present in the straw.
Keywords:Bentazon  herbicides  lignin peroxidase  manganese peroxidase  Phanerochaete chrysosporium  solid substrate fermentation  white rot fungus
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