| Research Abstract |
Polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) are ubiquitous environmental toxicants whose chemical stability and lipophilicity allow them to persist in the environment and in living organisms. White-rot fungi can degrade lignin, a complex high-molecular-weight aromatic polymer, and a wide spectrum of recalcitrant organopollutants, including polycyclic aromatic hydrocarbons, and polychlorinated biphenyls, polychlorinated phenols and PCDDs.
A degradation experiment on PCDDs and phylogenetical analyses were carried out on newly isolated 2,7-dichlorodibenzo-p-dioxin (2,7-diCDD)-degrading white-rot fungi. When these fungi were incubated with tri- or tetra-CDDs, the substrates were degraded efficiently, and hydroxylated metabolites were detected. Phlebia genera species were used for a degradation experiment on 2,7-diCDD and 1,3,6,8-tetraCDD. Phlebia acerina and Phlebia brevispora degraded 2,7-diCDD about 40% and 80%, respectively, over 14 days' incubation. It became cle
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ar that P. brevispora can degrade 1,3,6,8-tetraCDD and transform it to monohydroxy-tetraCDD, monomethoxy-tetraCDD, dimethoxy-tetraCDD, dimethoxy-triCDD and 3,5-dichlorocatechol in the treatment cultures.
Furthermore, we examined the effectiveness of the bioremediation method for the soil contaminated by dioxins. Results from this study were as follows:
1)The strain "Phlebia brevispora" can grow well in the soil environment.
2)The degradation of 2,7-DCDD by using P. brevispora in contaminated soil is confirmed, and decreasing rate is 50% in organic-poor soil and 42% in organic-rich soil respectively.
3)There has a possibility of inhibition of dioxin degradation by the existence of organic material in soil, but the addition of nutrients helps to facilitate to degrade dioxin by P. brevispora.
As a conclusion, there is a possibility to establish the remediation method for the soil by using "Phlebia brevispora" regardless of the soil property, however, it is important to control the amount of nutrient in the environment. Less
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