## 3 Results and Discussion
### Pollutant Disappearance Experiments
#### 3.1.4. Surfactant Degradation  
The use of different surfactants can stimulate desorption of hydrophobic pollutants from soil and increase their bioavailability [16; 17]. Often Tween-40, Tween-80, and Triton X-100 are used. For example, PAH degradation in polluted soil by _P. ostreatus_ can be increased with Tween-40, Tween-80, and Triton X-100 [59; 60]. Tweens do not affect the growth of fungi and are catabolized by them [61]. Significant range of the surfactants (such as oxyethylated alkylphenols) often more effectively increases the solubility of hydrophobic compounds. However, some surfactants themselves are very difficult to degrade, resulting in the formation of stable and toxic end products and their accumulation in the environment [18; 19]. The possibility of practical use of these compounds in bioremediation processes can be limited by their resistance to degradation. In addition, a result of their degradation can be the formation of stable and toxic alkylphenols as final products. Bacterial degradation of this class of compounds has been studied quite well, but the information on their degradation by fungi is limited [62]. We used neonol AF9-12 as an example of oxyethylated alkylphenols. Although it was not toxic for all the fungi studied, only 17 fungi metabolized this compound, and the degree of degradation and the site of the attack of its molecule are different (Figure 4). The use of spectrophotometric methods [28; 29] revealed that basidiomycetes _P. ostreatus_ f. Florida, _P. ostreatus_ MUT977, _P. ostreatus_ 336, _P. ostreatus_ LE-BIN0432, _B. adusta, 7--Len. betulina_, and ascomycete _C. herbarum_ attacked the oxyethyl chain, while the aromatic ring remained intact. _S. rugososanmulata_ and _T. ochracea_ degraded the aromatic ring. Figure 4: The disappearance of neonol AF9-12 by studied fungi: 1—_P. ostreatus_ f. Florida, 2—_P. ostreatus_ MUT2977, 3—_P. ostreatus_ 336, 5—_P. ostreatus_ LE-BIN0432, 6—_B. adusta, 7—Len. betulina_, 9—_Sch. commune_, 10—_Str. rugososanmulata_, 11—_T. versicolor_ DSM11372, 12—_T. versicolor_ MUT3403, 13—_T. hirsuta_, 14—_T. maxima_, 15—_T. ochracea_, 16—_T. gibbosa_, 18—_F. oxysporum_, 19—_G. candidatum_, 20—_C. herbarum_; \(\blacksquare\)—oxyethyl chain, \(\blacksquare\)—aromatic ring. Finally, another nine species of the fungi, including basidiomycetes _L. betulina, T. versicolor_ DSM, _T. versicolor_ MUT, _T. hirsuta, T. maxima_, and _T. gibbosa_, and ascomycetes _L. aphanocladii, F. oxysporum_, and _G. candidum_, destroyed both parts of the neonol molecule (Figure 4). The cleavage of the oxyethyl side chain leads to the formation of the alkylphenols. In our work we used issonylphenol as model of alkylphenols to study the activity of fungi. Issonylphenol decreased the growth of the most studied fungi, as evidenced by the significant decrease of the amount of biomass compared to the control treatment (Figure 5A). The exceptions were fungi _S. murashkinskyi, T. hirsuta, T. ochracea, F. oxysporum_, and _G. candidum_. The amounts of the mycelium of these fungi in the control treatments and in the presence of issonylphenol were approximately the same. An increase (by 1.5 times) of biomass of _F. oxysporum_ in the presence of this pollutant was found. Among 20 studied fungi, only six species of basidiomycetes (_T. versicolor_ MUT, _L. betulina, P. ostreatus_ f. Florida, _S. rugosoanulata_, _S. commune_) and one ascomycete (_C. herbarum_) could degrade isonylphenol. The most active degrader of the isonylphenol was _S. commune_; the disappearance was 61% after 14 days of cultivation at the start concentration of 200 mg/L (Figure 5A). Infrared spectroscopy is widely used to study the fine structural changes in molecules of various chemical compounds and materials. This method is widely used in studying the ways of degradation of various alkylphenols [63; 64; 65]. We used fungi to study changes in surfactant structure during fungal degradation: _P. ostreatus_ Florida (attacked the oxyethyl chain), _S. rugosoanulata_ (degraded the aromatic ring), _T.