(2,4,8-triCDF) at different extents (lower than for dichlorodibenzo-p-dioxins), but it
was completely unable to transform 1,3,6,8-, 1,3,7,8-, and 1,2,8,9-tetraCDDs during
the same incubation period.
22.5 Non-chlorinated Aromatic Pollutants
22.5.1 Polycyclic Aromatic Hydrocarbons
Polycyclic aromatic hydrocarbons (PAHs), unlike the contaminants (PCBs, PCDDs,
and PCDFs) described so far, are natural compounds. However, most of them arise
from the incomplete combustion of fossil fuels and biomasses associated with
different industrial activities. From a chemical viewpoint, PAHs consist of two or
more fused benzene rings arranged either in a linear or a cluster mode. They are
included among priority pollutants owing to their toxic, mutagenic, and, in some
cases, carcinogenic properties (Haritash and Kaushik 2009). Their hydrophobicity,
toxicity, and recalcitrance to biodegradation processes increase as the molecular
weight increases making PAHs particularly persistent in the environment.
To overcome bacterial degradation limitations, fungal transformation of PAHs
has extensively been studied over the last decades. Ligninolytic fungi, mostly WRFs
such as Trametes, Pleurotus, Phanerochaete, Bjerkandera, Irpex, Phlebia,
Nematoloma, and Lentinus spp. were demonstrated to efficiently metabolize PAHs
in model liquid cultures or in soils (Sack et al. 1997; Pointing 2001; D’Annibale
et al. 2005; Valentín et al. 2006; Giubilei et al. 2009; Novotný et al. 2009; Covino
et al. 2010a, b; Lladó et al. 2013).
Concerning the mycoremediation of PAH-contaminated soil, one of the first
studies dealt with the treatment of a historically aromatic hydrocarbonscontaminated soil (D’Annibale et al. 2005). Two WRFs, namely P. chrysosporium
NRRL 6361 and P. pulmonarius CBS 664.97 were tested for their ability to grow
under non-sterile conditions and to degrade various hydrocarbons. In the case of
naphthalene, both fungi completely removed this contaminant within 30 days of the
incubation. Fungal strains belonging to genera of Phanerochaete, Polyporus,
Stereum, Lentinus, Bjerkandera, Irpex, Pleurotus, and Phlebia were also screened
for their ability to degrade a mixture of PAHs (phenanthrene, fluoranthrene, pyrene,
and chrysene) in artificially spiked forest and marsh soils (Valentín et al. 2006).
Marsh soil test revealed that all fungi, with the exception of Phlebia ssp., were
capable of degrading the mixture of PAHs to some extent after 30 days of the
incubation. In particular, Pleurotus eryngii, B. adusta, and I. lacteus were the most
outstanding strains with an average degradation of PAHs being 67, 55, and 53%,
respectively. Furthermore, these three fungal strains partially degraded PAHs also
under saline conditions (marsh soil test).
A few years later, Covino and colleagues deeply investigated the effect of both
lignocellulosic substrate (inoculum carrier) and contaminant bioavailability on the
degradation performance of different fungal strains (L. tigrinus, I. lacteus,
452
T. Stella
was completely unable to transform 1,3,6,8-, 1,3,7,8-, and 1,2,8,9-tetraCDDs during
the same incubation period.
22.5 Non-chlorinated Aromatic Pollutants
22.5.1 Polycyclic Aromatic Hydrocarbons
Polycyclic aromatic hydrocarbons (PAHs), unlike the contaminants (PCBs, PCDDs,
and PCDFs) described so far, are natural compounds. However, most of them arise
from the incomplete combustion of fossil fuels and biomasses associated with
different industrial activities. From a chemical viewpoint, PAHs consist of two or
more fused benzene rings arranged either in a linear or a cluster mode. They are
included among priority pollutants owing to their toxic, mutagenic, and, in some
cases, carcinogenic properties (Haritash and Kaushik 2009). Their hydrophobicity,
toxicity, and recalcitrance to biodegradation processes increase as the molecular
weight increases making PAHs particularly persistent in the environment.
To overcome bacterial degradation limitations, fungal transformation of PAHs
has extensively been studied over the last decades. Ligninolytic fungi, mostly WRFs
such as Trametes, Pleurotus, Phanerochaete, Bjerkandera, Irpex, Phlebia,
Nematoloma, and Lentinus spp. were demonstrated to efficiently metabolize PAHs
in model liquid cultures or in soils (Sack et al. 1997; Pointing 2001; D’Annibale
et al. 2005; Valentín et al. 2006; Giubilei et al. 2009; Novotný et al. 2009; Covino
et al. 2010a, b; Lladó et al. 2013).
Concerning the mycoremediation of PAH-contaminated soil, one of the first
studies dealt with the treatment of a historically aromatic hydrocarbonscontaminated soil (D’Annibale et al. 2005). Two WRFs, namely P. chrysosporium
NRRL 6361 and P. pulmonarius CBS 664.97 were tested for their ability to grow
under non-sterile conditions and to degrade various hydrocarbons. In the case of
naphthalene, both fungi completely removed this contaminant within 30 days of the
incubation. Fungal strains belonging to genera of Phanerochaete, Polyporus,
Stereum, Lentinus, Bjerkandera, Irpex, Pleurotus, and Phlebia were also screened
for their ability to degrade a mixture of PAHs (phenanthrene, fluoranthrene, pyrene,
and chrysene) in artificially spiked forest and marsh soils (Valentín et al. 2006).
Marsh soil test revealed that all fungi, with the exception of Phlebia ssp., were
capable of degrading the mixture of PAHs to some extent after 30 days of the
incubation. In particular, Pleurotus eryngii, B. adusta, and I. lacteus were the most
outstanding strains with an average degradation of PAHs being 67, 55, and 53%,
respectively. Furthermore, these three fungal strains partially degraded PAHs also
under saline conditions (marsh soil test).
A few years later, Covino and colleagues deeply investigated the effect of both
lignocellulosic substrate (inoculum carrier) and contaminant bioavailability on the
degradation performance of different fungal strains (L. tigrinus, I. lacteus,
452
T. Stella