contaminants by non-specific radical-based reactions. WRFs are endowed also with
an intracellular enzymatic system involving cytochrome P450 monooxygenase
enzymes (Črešnar and Petrič 2011; Stella et al. 2013). This intracellular pathway,
which occurs in all eukaryotic organisms, mainly regulates the bioconversion
of hormones and the detoxification of drugs and xenobiotics (Bernhardt 2006).
In WRFs, CYP450 is implied as well as the ligninolytic system in the degradation
of xenobiotics (van den Brink et al. 1998; Stella et al. 2013). Moreover, as mentioned above, WRFs evolved a spatially extensive hyphal growth enabling them to
penetrate across air-filled soil pores, air-water interfaces, and even rock matrices
(Bornyasz et al. 2005) and act as dispersion vectors of bacteria (Kohlmeier et al.
2005; Bonfante and Anca 2009). Fungi can also tolerate high concentrations of
organic contaminants and heavy metals without deleterious effects on their enzyme
activities (Baldrian et al. 2000; Baldrian 2003; Tuomela et al. 2005).
Unlike bacteria, fungi cannot assimilate contaminants as a source of carbon and
energy; thus, they use the lignocellulosic residues as amendments to support their
growth in the co-metabolic process of contaminant degradation (Singh 2006).
Furthermore, fungi are involved in a soil humification process leading to decontamination and also to reuse of the soil for agricultural purposes (Bollag 1992;
Michels 1998). Therefore, from the circular economy strategy point of view, the
use of these organisms in soil remediation is highly recommended.
Nevertheless, mycoremediation has not been considered yet as a method for
consistently recovering contaminated soils or sediments at pilot-scale level, but the
number of bench-scale studies is increasing over time in view of their potential
applications. Within this frame, a number of laboratory studies and also semi- and
pilot-scale studies concerning the mycoremediation of soils contaminated by recalcitrant organic pollutants will be presented in the following sections.
22.4 Chlorinated Aromatic Pollutants
22.4.1 Polychlorinated Biphenyls
Polychlorinated biphenyls (PCBs) are synthetic compounds the structure of which
consists of a biphenyl molecule that carries from one to ten chlorine atoms. In the
past, chemical, petrochemical, paint and coating industries widely used PCB mixtures because of their thermal and chemical stability, flame resistance, and dielectric
properties. Consequently, their use led to an extensive environmental contamination
either through accidental releases or inappropriate methods of disposal. Owing to
their aforementioned inertness, PCBs are still present in those areas where industrial
activities based on their use had been carried out for decades, although their
production and application were banned long time ago. PCBs rank among the
most hazardous contaminants in the world; thus, they are at the forefront of public
health concern. Indeed, the teratogenic, carcinogenic, and endocrine-disrupting
effects of these xenobiotics have been widely reported in the literature (Crinnion
448
T. Stella
an intracellular enzymatic system involving cytochrome P450 monooxygenase
enzymes (Črešnar and Petrič 2011; Stella et al. 2013). This intracellular pathway,
which occurs in all eukaryotic organisms, mainly regulates the bioconversion
of hormones and the detoxification of drugs and xenobiotics (Bernhardt 2006).
In WRFs, CYP450 is implied as well as the ligninolytic system in the degradation
of xenobiotics (van den Brink et al. 1998; Stella et al. 2013). Moreover, as mentioned above, WRFs evolved a spatially extensive hyphal growth enabling them to
penetrate across air-filled soil pores, air-water interfaces, and even rock matrices
(Bornyasz et al. 2005) and act as dispersion vectors of bacteria (Kohlmeier et al.
2005; Bonfante and Anca 2009). Fungi can also tolerate high concentrations of
organic contaminants and heavy metals without deleterious effects on their enzyme
activities (Baldrian et al. 2000; Baldrian 2003; Tuomela et al. 2005).
Unlike bacteria, fungi cannot assimilate contaminants as a source of carbon and
energy; thus, they use the lignocellulosic residues as amendments to support their
growth in the co-metabolic process of contaminant degradation (Singh 2006).
Furthermore, fungi are involved in a soil humification process leading to decontamination and also to reuse of the soil for agricultural purposes (Bollag 1992;
Michels 1998). Therefore, from the circular economy strategy point of view, the
use of these organisms in soil remediation is highly recommended.
Nevertheless, mycoremediation has not been considered yet as a method for
consistently recovering contaminated soils or sediments at pilot-scale level, but the
number of bench-scale studies is increasing over time in view of their potential
applications. Within this frame, a number of laboratory studies and also semi- and
pilot-scale studies concerning the mycoremediation of soils contaminated by recalcitrant organic pollutants will be presented in the following sections.
22.4 Chlorinated Aromatic Pollutants
22.4.1 Polychlorinated Biphenyls
Polychlorinated biphenyls (PCBs) are synthetic compounds the structure of which
consists of a biphenyl molecule that carries from one to ten chlorine atoms. In the
past, chemical, petrochemical, paint and coating industries widely used PCB mixtures because of their thermal and chemical stability, flame resistance, and dielectric
properties. Consequently, their use led to an extensive environmental contamination
either through accidental releases or inappropriate methods of disposal. Owing to
their aforementioned inertness, PCBs are still present in those areas where industrial
activities based on their use had been carried out for decades, although their
production and application were banned long time ago. PCBs rank among the
most hazardous contaminants in the world; thus, they are at the forefront of public
health concern. Indeed, the teratogenic, carcinogenic, and endocrine-disrupting
effects of these xenobiotics have been widely reported in the literature (Crinnion
448
T. Stella