Biodegradation and toxicity reduction of nonylphenol, 4-tertoctylphenol and 2,4-dichlorophenol by the ascomycetous fungus Thielavia sp HJ22: Identification of fungal metabolites and proposal of a putative pathway

Abstract

Research on the biodegradation of emerging pollutants is gaining great focus due to their detrimental effects on the environment and humans. The objective of the present study was to evaluate the ability of the ascomycetes Thielavia sp. HJ22 to remove the phenolic xenobiotics nonylphenol (NP), 4-tert-octylphenol (4-tert-OP), and 2,4-dichlorophenol (2,4-DCP). The strain showed efficient degradation of NP and 4-tert-OP with 95% and 100% removal within 8 hours of incubation, respectively. A removal rate of 80% was observed with 2,4-DCP within the same time. Under experimental conditions, the degradation of the tested pollutants increased concomitantly with laccase production and cytochrome P450 monooxygenases inhibition. This study demonstrated the involvement of laccase in pollutants removal together with biosorption mechanisms. Additionally, results showed the participation of cytochrome P450 monooxygenase in the elimination of 2,4-DCP. Liquid chromatography-mass spectrometry analysis revealed several intermediates, mainly hydroxylated and oxidized compounds, with less harmful effects compared to the parent compounds. A decrease in the toxicity of the identified metabolites was observed using Aliivibrio fischeri as a bioindicator. The metabolic pathways of degradation were proposed based on the identified metabolites. The results point out the potential of Thielavia strains in the degradation and detoxification of phenolic xenobiotics.