Monocyclic Aromatic Hydrocarbons

The BTEX compounds (benzene, toluene, ethylbenzene, and the xylene isomers) are toxic components of liquid fuels (Ritchie et al. 2001). They are also commonly used in industry as solvents and chemical feedstocks. Toluene and ethyl-benzene support the growth of a few fungi, which have consequently been used for the bioremediation of the volatile components of toxic wastes (Prenafeta-Boldii et al. 2001). Benzene and xylenes do not appear to serve as carbon or energy sources for fungi, although there are reports of the fungal cometabolism of benzene to phenol (Griffin and Cooney 1979) and even of its mineralization to CO2 (Yadav and Reddy 1993).

Toluene is utilized as a carbon and energy source by Cladosporium sphaerospermum, Scedosporium apiospermum [the anamorph of P. boydii], Cladophialophora sp., Exophiala sp., and Pseudeurotium zonatum; these fungi may be used in biofilters to clean up toluene in waste gases (Garcia-Pena et al. 2001; Prenafeta-Boldu et al. 2001; Weber et al. 1995). In high-nitrogen media, P. chrysosporium cometabolizes toluene to CO2 (Yadav and Reddy 1993).

Ethylbenzene is used as a growth substrate by C. sphaerospermum, Cladophialophora sp., and Exophiala sp. (Prenafeta-Boldu et al. 2001) and is cometabolized by P. chrysosporium (Yadav and Reddy 1993). Fusarium moniliforme [F. verticillioides] oxidizes ethylbenzene and propylbenzene to (+ )-1-phenylethanol and (+)-1-phenyl-propanol, respectively (Uzura et al. 2001).

The o-, m-, and p-isomers of xylene are all cometabolized by P. chrysosporium but the products are unknown (Yadav and Reddy 1993). Several other dialkylbenzenes, such as 1,4-di-tert-butylbenzene, are hydroxylated on the methyl groups by Sporotrichum sulfurescens [B. bassiana] (Johnson et al. 1973).

Styrene (C6H5CH=CH2) serves as a growth substrate for Exophiala jeanselmei, C. sphaerospermum, and Cladophialophora sp. (Cox et al. 1996; Prenafeta-BoldU et al. 2001). In E. jeanselmei, it is oxidized by a cytochrome P450 monooxygenase to styrene oxide, which is converted to phenylacetaldehyde and phenylacetic acid (Cox et al. 1996). P. ostreatus oxidizes styrene to

Figure 3 Structures of several polycyclic aromatic hydrocarbons.

phenyl-1,2-ethanediol and other products (Braun-Lüllemann et al. 1997).

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