## 6 Types and Mechanisms of Removing Xenobiotics from Water
### Types of Lacase- Assisted Removing Xenobiotics from Water
#### 6.1.2 PAHs (Polycyclic Aromatic Hydrocarbons)
Bioremediation, due to the relatively low cost and greater efficiency for compounds with a high degree of structural complexity, is one of the widely used technologies in the removal of pollutants [200]. The most promising class of enzymes for PAH detoxification are oxidoreductaseases [206, 207, 208, 209]. Oxidoreductase include lacases, which catalyze reactions with a wide range of aromatic impurities, such as phenols and PAHs as substrates [201]. The fungus _Trematophoma_ sp. UTMC5003 isolated from soil in Iran could, in the future, be used in the bioremediation of oil-contaminated soils and water. The isolate obtained by [PERSON] et al. (2017) is capable of producing biosurfactant and lacase. The fungus degraded 70% of crude oil and 90% of aliphatic compounds and down to 56, 87 and 90% of pyren, anthracen, phenanthrene respectively, within 15 days. _Trematophoma_ sp. UTMC 5003 produced 4U/L of lacases in the appearance of petroleum as a carbon source [179]. The lacases produced by _Leucoapericus gongylophorus_ FF-2006, from _Atta sexdens rubropilosa_, were tested for their ability to degrade several PAHs, which are important in aquatic degradation. Degradation reactions were carried out in an aqueous buffer solution at pH 6.0 in the presence of Tween-20 and 50 U/L lacase preparation at 30 \({}^{\circ}\)C, with constant magnetic stirring without mediators. Over 70% of the anthracene, 40% of the fluorene and 25% of the phenanthrene were biodegraded within 24 h. The enzyme degraded anthracene to anthrone and anthraquinone. It should be noted that anthraquinones have significant biological activity, such as laxative, anti-inflammatory and anticancer, as well as antimalarial, antiviral and antifungal properties. No metabolites degrading other PAHs were observed, probably due to their water solubility and low concentration [201]. Using _P. ostreatus_ lacase, it was possible to completely remove naphthalene and more than 90% of anthracene and 1,10-phenanthroline from the reaction mixture during 5, 11 and 14 days of incubation, respectively. Naphthalene was selected as a model compound for the analysis of the metabolic pathway of PAH degradation. Based on the obtained metabolites,the researchers proposed the course of naphthalene degradation using _P. ostratus_ and its enzymes, naphthalene dioxygenase and lacases. The final product of the reaction was benzoic acid [212], the simplest aromatic carboxylic acid with low toxicity and antibacterial and antifungal activity, most often used in the food industry and cosmetics. In addition, a higher level of the degradation of naphthalene was observed compared to anthracene and 1,10-phenanthroline, further supporting the idea that low molecular weight PAHs are more easily degraded due to their higher solubility and greater bioavailability. It should also be noted that macromolecular organic compounds, such as PAHs, are degraded not by single enzymes but by the cooperation of two or more enzymes. This is confirmed in studies by [PERSON] et al. (2018) in which the authors suggest that lacase can catalyze the initial attack on the PAH molecule, which leads to the formation of quinones, and their further oxidation is provided by the peroxidase, which ultimately leads to PAH mineralization [213]. [PERSON] et al. (2017) investigated the potential of extracellular crude enzyme extracts of _Ganoderma_ sp., a white rot fungus (WRF), from urban ecosystems in Havana, Cuba, to degrade PAHs and noted that _Ganoderma_ strains degraded three PAHs (naphthalene, phenanthrene and fluorene) with different efficiency. The presence of HBT, a synthetic mediator, significantly increased the degradation of the studied PAHs. Nevertheless, one strain, _Ganoderma_ sp. UH-M, was able to degrade PAHs with the same efficiency with and without a redox mediator, which is advantageous in practical applications [214]. In contrast to the degradation pathway proposed by [PERSON] et al. (2019) led by _P.