## 3 Results and Discussion
### Pollutant Disappearance Experiments  
#### 3.1.1 Polycyclic Aromatic Hydrocarbons (PAHs)  
The considerable interest in biodegradation mechanisms and environmental fate of PAHs is due to their wide distribution, resistance to degradation, accumulation in soils and sediments, and toxic, mutagenic, and carcinogenic properties [15]. Many reviews on the biodegradation of this class of pollutant are available. The corresponding quinones (e.g., 9,10-anthraquinone, phenanthrene-9,10-quinone, and benzo[a]anthracene-7,12-quinone) are discussed as the main metabolites [38; 49]. The three-ring PAHs used in our experiments (phenanthrene, anthracene, and fluorene) are not mutagenic or carcinogenic to humans [15]. However, they are often used as model compounds for the study of the biodegradation of PAHs. They are found in PAH-containing samples, and many PAH derivatives are carcinogenic. In our experiments, all fungi actively removed PAHs, as evidenced by the decrease in their concentration after 14 days of cultivation (Table 1). Previous experiments showed that PAH sorption by living fungal mats was significantly lower than that by heat-killed ones. This finding agrees with the data of [PERSON] and [PERSON] [50]. According to the data obtained, we used two consistent extraction procedures: (1) extraction from full contents of the flasks; (2) the cultivation medium was separated from mycelia, and the mycelium was extracted again. Insignificant sorption of the studied PAHs to mycelia (5-7%) was shown. In general, the basidiomycetes removed these compounds more actively than did the ascomycetes (Table 1). Anthracene was the least available to all fungi. The disappearance of this compound varied from 16 to 91% with the basidiomycetes. Anthracene was inaccessible to the ascomycetes _F. oxysporum_ and _G. candidium_. Phenanthrene and fluorene were removed by both basidio- and ascomycetes (17.7-100 and 16.8-100%, respectively) (Table 1). The degradative activity towards PAHs showed both strain and species differences. Within the species _Pleurotus ostreatus_, the most active was _P. ostreatus_ D1 (the disappearance of phenanthrene and fluorene reached 100%). Within the genus _Trametes_, both _T. versicolor_ and _T. maximua_ strains were active degraders, whereas _T. gibbosa_ was not very active. One of the most active degraders was the ascomycete _C. herbarum_ which showed a removal efficiency of about 100% with all PAHs used. The literature has a single report on the degradation of PAHs by another member of this genus, _C. spharososperm_. However, in that study, the disappearance of three-ring PAHs did not exceed 35% [44]. GC analysis revealed the presence of additional peaks of products of degradation of anthracene, phenanthrene, and fluorene by the studied fungi. These products were identified as 9,10-anthraquinone (RT = 4.51 min), phenanthrene-9,10-quinone (RT = 5.04 min), and 9-fluorenone (RT = 4.33 min) in the case of anthracene, phenanthrene, and fluorene oxidation, respectively. The products of deeper PAH degradation, such as 2-carboxybenzaldehyde, 2,2\({}^{\prime}\)-diphenic and phthalic acids, were identified with all studied members of the genera _Trantes_ and _Pleutrotus_, and with _S. commune_. When the growth time was extended, these compounds disappeared, which suggests their involvement in the basal metabolism [51]. It should be noted that the revealed metabolites of three-ring PAH degradation by the basidio- and ascomycetes were identical. The most active degraders of three- and four-ring PAHs were the basidiomyectes _B. adusta, P. ostreatus_ (all strains used), _S. commune, T. maxima_, and _T. versicolor_ (both strains used), and two ascomycetes _C. herbarum_ and _L. aphanocladii_ (Table 1). Although _S. murashkinskyi_ revealed a high degradative activity towards PAHs, it was a slowly growing fungus that can complicate its following practical use. However, despite its average degradative activity, the litter-decomposing _S.