Biodegradation of nonylphenol polyethoxylates by litter-basidiomycetous fungi

Abstract

Nonylphenol polyethoxylates (NPnEOs) are widely used surfactants whose degradation products are a matter of concern due to their greater persistence in the environment, toxicity and endocrine-disrupting effects in wildlife and humans. The saprotrophics Gymnopus luxurians and Hypholoma fasciculare, and the ectomycorrhizal Xerocomellus chrysenteron were selected among nineteen litter-decomposing fungi due to their capacity to tolerate up to 10 g L-1 of NP10EO. While X. chrysenteron was unable to remove NP10EO when amended to agar medium at 1 g L-1, G. luxurians and H. fasciculare were efficient degraders, reaching 37.5 ± 3.1% and 74.4 ± 4.4% of elimination after 15 days, respectively. Under solid-state fermentation using Ligustrum lucidum leaf-litter as substrate, G. luxurians and H. fasciculare removed correspondingly 71.3 ± 3.8% and 96.3 ± 1.4% of the surfactant after 90 days. Fungal degradation ability was related to the secreted titers of the ligninolytic enzymes laccase and manganese peroxidase. Degradation pathway involved the elimination of the shorter homologues (n ≤ 7) while carboxylated products were not detected, consequently potentially toxic metabolites did not accumulate. Therefore, these litter-basidiomycetous fungi showed as promising tools for detoxifying nonylphenol polyethoxylates and other related chemical compounds with endocrine disrupting activity (such as nonylphenol).