Biotransformation of the polycyclic musks HHCB and AHTN and metabolite formation by fungi occurring in freshwater environments.

Micropollutants found in aquatic environments have increasingly raised concerns with respect to their uncertain environmental fate and potentially adverse effects on human health and the environment. The biodegradability of two major representatives of the polycyclic musk fragrances, Galaxolide (HHCB) and Tonalide (AHTN), and the formation of biotransformation metabolites, were investigated with Myrioconium sp. strain UHH 1-13-18-4 and Clavariopsis aquatica, two mitosporic fungi derived from freshwater environments. A particular focus was to assess the effects of extracellular oxidoreductases such as laccases, which are produced by the investigated fungi under certain conditions, on HHCB and AHTN. The fungi converted HHCB and AHTN into various products via initial hydroxylation at different carbon positions. Further metabolism resulted in the subsequent formation of diketone, peroxide, and O-methylated derivatives. Isolated laccases of the investigated fungi were able to oxidize HHCB and AHTN and catalyzed the formation of the metabolite HHCB-lactone from HHCB. At particular environmental situations also specified within the present study, biotransformations catalyzed by fungi occurring in freshwater environments may be considered when addressing the fate of polycyclic musks in freshwater systems and potential biological effects of their degradation metabolites.