BIOTRANSFORMATION OF THE MAJOR FUNGAL METABOLITE 3,5-DICHLOROP-P-ANISYL ALCOHOL UNDER ANAEROBIC CONDITIONS AND ITS ROLE IN FORMATION OF BIS(3,5-DICHLORO-4-HYDROXYPHENYL)METHANE

Higher fungi have a widespread capacity for biosynthesis of organohalo gens, Commonly occurring chloroaromatic fungal metabolites can end up in anaerobic microniches at the boundary of fungal colonies and wetlan d soils. The aim of this study was to investigate the environmental fa te of a major fungal metabolite, 3,5-dichloro-p-anisyl alcohol, under anaerobic conditions. This compound was incubated with methanogenic sl udge to study its biotransformation reactions. Initially, 3,5-dichloro -p-anisyl alcohol was readily demethylated in stoichiometric quantitie s to 3,5-dichloro-4-hydroxybenzyl alcohol. The demethylated product wa s converted further via two routes: a biotic route leading to the form ation of 3,5-dichloro-3-hydroxybenzoate and 2,6-dichlorophenol, as wel l as an abiotic route leading to the formation of bis (3,5-dichloro-4- hydroxyphenyl) methane. In the first route, the benzyl alcohol moiety on the aromatic ring was oxidized, giving 3,5-diehloro-4-hydroxybenzoa te as a transient or accumulating product, depending on the type of me thanogenic sludge used. In sludge previously adapted to low-molecular- weight lignin from straw, a part of the 3,5-dichloro-4-hydroxybenzoate was decarboxylated, yielding detectable levels of 2,6-dichlorophenol, In the second route, 3,5-dichloro-4-hydroxybenzyl alcohol dimerized, leading to the formation of a tetrachlorinated bisphenolic compound, w hich was identified as bis (3,5-dichloro-4-hydroxyphenyl) methane. Sin ce formation of this dimer was also observed in incubations with autoc laved sludge spiked with 3,5-dichloro-4-hydroxybenzyl alcohol, it was concluded that its formation was due to an abiotic process. However, d emethylation of the fungal metabolite by biological processes was a pr erequisite for dimerization, The most probable reaction mechanism lead ing to the formation of the tetrachlorinated dimer in the absence of o xygen is presented, and the possible environmental implications of its natural occurrence are discussed.