another strain of Phanerochaete (P. sordida) was studied for its capability of
degrading a mixture of 10 tetra- to octachlorodibenzo-p-dioxins and furans (Takada
et al. 1996). Moreover, strains belonging to Phlebia and Bjerkandera genera were
also proved to be efficient in metabolizing both polychlorinated dibenzo-p-dioxins
and furans (Mori and Kondo 2002; Kamei and Kondo 2005; Kamei et al. 2005;
Manji and Ishihara 2004). Other WRFs were also studied for their ability to degrade
dibenzo-p-dioxins as reviewed by Pinedo-Rivilla et al. (2009): several studies
reported the capability of Trametes sp. CH2, Irpex sp. W3, and Pleurotus
pulmonarius to mediate the hydroxylation and methoxylation of PCDDs
(Yamaguchi et al. 2007; Nam et al. 2008).
Due to the promising results achieved in liquid fungal cultures, a recent study
focused on the feasibility of treating actual PCDD- and PCDF-contaminated soils by
fungi. Anasonye et al. (2015) firstly performed a 30-day screening of six fungal
strains to assess their ability to grow on historically contaminated soils. Pine bark
was used as lignocellulosic substrate to inoculate the soils. Two strains, namely
Phanerochaete velutina and Stropharia rugosoannulata, were then selected to carry
out the treatment of a PCDD- and PCDF-contaminated soil from a sawmill site: glass
bioreactors were filled with contaminated soil mixed with fungal inoculum grown on
pine bark. Bioreactors were incubated for 90 days and continuously aerated with
moist air. Bioaugmentation with P. velutina and S. rugosoannulata brought about
62% and 64% of PCDD and PCDF degradation, respectively.
On the other hand, a limited number of studies dealt with PCDDs and PCDFs
degradation by non-ligninolytic fungi. A dioxin-degrading organism was isolated
from the activated sludge of a landfill treatment plant and identified as Acremonium
sp. (Nakamiya et al. 2002). This fungus (later identified as Pseudallescheria boydii)
was tested for the degradation of a mixture of highly chlorinated dioxins (2 ng/mL):
this fungal culture was able to remove up to 82% of the mixture with respect to the
initial concentration in one day under denitrifying conditions. Due to these promising results, P. boydii was further used in a slurry bioreactor system for the treatment
of dioxin-contaminated soils (Ishii and Furuichi 2007). However, P. boydii was not
able to remove the dioxins up to the environmental standard level, and, thus, the
mycoremediation treatment was coupled with a physicochemical process (ethanol
extraction) to reach the required quality standard. Two years after, the same authors
demonstrated that this fungus requires glucose as carbon source to grow and degrade
2,3,7,8-tetraCDD through a co-metabolic process (Ishii et al. 2009).
Among ascomycetes, the cyclic ether degrading fungus Cordyceps sinensis was
proved to degrade not only non-chlorinated dioxins, but also 2,3,7-trichlorodibenzop-dioxin and octachlorodibenzo-p-dioxin (Nakamiya et al. 2005). Chemical analyses
revealed that the concentration of chlorinated dioxins halved after 50 days of
incubation with the fungus leading to the formation of chlorocatechols as biotransformation products. A few years later, another strain of Cordyceps (C. militaris) was
tested in liquid cultures for di-, tri-, and tetra-CDD degradation activity (Mori et al.
2015). In this case, only 55% of 2,7-diCDD was degraded after 30 days of incubation in glucose-basal salt medium. This fungus was also able to degrade 2,3,7trichlorodibenzo-p-dioxin (2,3,7-triCDD) and 2,4,8-trichlorodibenzo-p-furan
22 Mycoremediation of Contaminated Soils
451
degrading a mixture of 10 tetra- to octachlorodibenzo-p-dioxins and furans (Takada
et al. 1996). Moreover, strains belonging to Phlebia and Bjerkandera genera were
also proved to be efficient in metabolizing both polychlorinated dibenzo-p-dioxins
and furans (Mori and Kondo 2002; Kamei and Kondo 2005; Kamei et al. 2005;
Manji and Ishihara 2004). Other WRFs were also studied for their ability to degrade
dibenzo-p-dioxins as reviewed by Pinedo-Rivilla et al. (2009): several studies
reported the capability of Trametes sp. CH2, Irpex sp. W3, and Pleurotus
pulmonarius to mediate the hydroxylation and methoxylation of PCDDs
(Yamaguchi et al. 2007; Nam et al. 2008).
Due to the promising results achieved in liquid fungal cultures, a recent study
focused on the feasibility of treating actual PCDD- and PCDF-contaminated soils by
fungi. Anasonye et al. (2015) firstly performed a 30-day screening of six fungal
strains to assess their ability to grow on historically contaminated soils. Pine bark
was used as lignocellulosic substrate to inoculate the soils. Two strains, namely
Phanerochaete velutina and Stropharia rugosoannulata, were then selected to carry
out the treatment of a PCDD- and PCDF-contaminated soil from a sawmill site: glass
bioreactors were filled with contaminated soil mixed with fungal inoculum grown on
pine bark. Bioreactors were incubated for 90 days and continuously aerated with
moist air. Bioaugmentation with P. velutina and S. rugosoannulata brought about
62% and 64% of PCDD and PCDF degradation, respectively.
On the other hand, a limited number of studies dealt with PCDDs and PCDFs
degradation by non-ligninolytic fungi. A dioxin-degrading organism was isolated
from the activated sludge of a landfill treatment plant and identified as Acremonium
sp. (Nakamiya et al. 2002). This fungus (later identified as Pseudallescheria boydii)
was tested for the degradation of a mixture of highly chlorinated dioxins (2 ng/mL):
this fungal culture was able to remove up to 82% of the mixture with respect to the
initial concentration in one day under denitrifying conditions. Due to these promising results, P. boydii was further used in a slurry bioreactor system for the treatment
of dioxin-contaminated soils (Ishii and Furuichi 2007). However, P. boydii was not
able to remove the dioxins up to the environmental standard level, and, thus, the
mycoremediation treatment was coupled with a physicochemical process (ethanol
extraction) to reach the required quality standard. Two years after, the same authors
demonstrated that this fungus requires glucose as carbon source to grow and degrade
2,3,7,8-tetraCDD through a co-metabolic process (Ishii et al. 2009).
Among ascomycetes, the cyclic ether degrading fungus Cordyceps sinensis was
proved to degrade not only non-chlorinated dioxins, but also 2,3,7-trichlorodibenzop-dioxin and octachlorodibenzo-p-dioxin (Nakamiya et al. 2005). Chemical analyses
revealed that the concentration of chlorinated dioxins halved after 50 days of
incubation with the fungus leading to the formation of chlorocatechols as biotransformation products. A few years later, another strain of Cordyceps (C. militaris) was
tested in liquid cultures for di-, tri-, and tetra-CDD degradation activity (Mori et al.
2015). In this case, only 55% of 2,7-diCDD was degraded after 30 days of incubation in glucose-basal salt medium. This fungus was also able to degrade 2,3,7trichlorodibenzo-p-dioxin (2,3,7-triCDD) and 2,4,8-trichlorodibenzo-p-furan
22 Mycoremediation of Contaminated Soils
451