| In this series of studies, Trametes villosa laccase as a model enzyme, birnessite, ferrihydrite and aluminum hydroxide as model metal oxides, 2,4-dichlorophenol (2,4-DCP) as a model xenobiotic, and catechol as a model humic precursor were used for this study.; The capacity of biotic and abiotic catalysts to incorporate chlorophenols and the potential of both catalysts to remediate soil polluted with chlorophenols were also determined. Two soils from Pennsylvania with 2.8 or 7.4% organic matter contents (Soils 1 and 2, respectively) were amended with 14 C-labeled 2,4-DCP and 4-chlorophenol (4-CP) incubated with a laccase (free or immobilized on montmoriilonite), or three poorly crystalline metal oxides. After treatment with laccases, 2,4-DCP was either transformed to methanol-soluble polymeric products (11--32%) or covalently bound to soil organic matter (53--85%); unaltered 2,4-DCP could be recovered from soil by methanol extraction (0--38%) at the completion of a 14-day incubation period. In Soil 1, both free and immobilized laccase removed 100% of 2,4-DCP without regard for moisture conditions. In Soil 2, immobilized laccase removed more 2,4-DCP than free enzyme. Binding of 2,4-DCP in the humin fraction was nearly the same for free and immobilized laccase. In general, immobilized laccase performed better than free laccase.; After a 3-d incubation with birnessite, up to 77% of 4-CP was transformed and covalently bound to Soil 1, while up to 71% of 2,4-DCP was disappeared from Soil 1. There was no significant difference in bound residue of 2,4-DCP between Soil 1 and 2. Binding of both chlorophenols in soil occurred on the humin fraction. Ferrihydrite and aluminum hydroxide showed significantly less ability to remove both chlorophenols from Soil 1 and 2 than birnessite.; To investigate the interaction between Trametes villosa laccase, poorly crystalline metal oxides, and a naturally occurring phenolic compound (catechol), these three components were monitored during incubation period. Birnessite had an inhibitory effect on the disappearance (transformation and adsorption) of catechol from solutions in the presence of laccase, while aluminum hydroxide and ferrihydrite had additive effects. (Abstract shortened by UMI.)... |
