Degradation of the xenoestrogen nonylphenol by aquatic fungi and their laccases

Abstract

Degradation of technical nonylphenol (t-NP), known as an endocrine-disrupting compound mixture, was assessed, using the mitosporic fungal strain UHH 1-6-18-4 isolated from nonylphenol-contaminated river water, and a strain of the aquatic hyphomycete Clavariopsis aquatica. GC-MS analysis could resolve 12 peaks attributable to nonyl chain-branched t-NP isomers. All were degraded, to individual extents. Analysis of degradation metabolites suggested intracellular hydroxylation of the nonyl moieties of individual t-NP isomers. Further metabolites also indicated shortening of branched nonyl chains, and 4-hydroxybenzoic acid was identified as a t-NP breakdown product in UHH 1-6-18-4. The t-NP degradation efficiency was higher in UHH 1-6-18-4 than in C. aquatica, and a lower specificity in degradation of individual t-NP constituents in UHH 1-6-18-4 than in C. aquatica was observed. Strain UHH 1-6-18-4 concomitantly produced extracellular laccase under degradation conditions. A mixture of CuSO 4 and vanillic acid considerably enhanced laccase production in both fungi. Laccase preparations derived from UHH 1-6-18-4 and C. aquatica cultures also converted t-NP. Laccase-catalysed transformation of t-NP led to the formation of products with higher molecular masses than that of the parent compound. These results emphasize a role of fungi occurring in aquatic ecosystems in degradation of water contaminants with endocrine activity, which has not previously been considered. Furthermore, the results are in support of two different mechanisms employed by fungi isolated from aquatic environments to initiate t-NP degradation: hydroxylation of individual t-NP isomers at their branched nonyl chains and further breakdown of the alkyl chains of certain isomers; and attack of t-NP by extracellular laccase, the latter leading to oxidative coupling of primary radical products to compounds with higher molecular masses. INTRODUCTIONNonylphenols have increasingly gained attention because of their potential to mimic the action of natural hormones in vertebrates (Ying et al., 2002). They result from incomplete biodegradation of nonylphenol polyethoxylates (NPEOs), which have been widely used as non-ionic surfactants in industrial processes and households (Braun et al., 2003;Ying et al., 2002). Both nonylphenols and NPEOs are discharged into the environment, mainly due to incomplete removal in wastewater treatment facilities (Ying et al., 2002). Nonylphenols are more resistant to biodegradation than their parent compounds and hence are found worldwide in wastewater treatment plant effluents and rivers in concentrations of up to the mg l 21 range (Heemken et al., 2001;Kolpin et al., 2002;Stachel et al., 2003;Ying et al., 2002). Due to their hydrophobicity, they tend to adsorb onto surface water particles and sediments and accumulate in aquatic organisms (Heemken et al., 2001;Ying et al., 2002). Consequently, nonylphenols represent a serious environmental and human health risk. The assessment of biodegradative processes affecting the environmental...

Isolation of a Nonylphenol-degrading Microbial Consortium

“…하지만, 수생환경에 잔류하는 난분해 성 물질의 제거 및 분해에 대한 연구는 대부분 수생식물을 이 용한 화학물질 흡착 및 수생 생태 환경의 복원에 대한 연구이 다 (Liao and Chang, 2004;Jayaweera and Kasturiarachchi, 2004). 하지만 nonylphenol의 생물학적 분해에 관하여서는 국 외에서도 nonylphenol 분해 미생물의 분리에 대한 보고만 되 어있는 정도이며 국내에서는 이에 대한 연구가 아직 이루어 지고 있지 않다 (Tanghe et al, 1999;Fujii et al, 2000;Fujii et al, 2001;Corvini et al, 2004;Junghanns et al, 2005;Shi and Bending, 2007 Table 2).…”

Intracellular proteome expression during 4-n-nonylphenol biodegradation by the filamentous fungus Metarhizium robertsii

“…Proteomic studies of filamentous fungi have only recently begun to appear in the literature, despite the prevalence of these organisms in the fields of biotechnology, industry and environmental protection and their importance as both human and plant pathogens (Kim et al 2007;Doyle 2011;Bregar et al, 2012;Salvachúa et al 2013;Kroll et al 2014). Although the fungal biodegradation pathways of 4-NP have been proposed for several fungal organisms (Junghanns et al 2005;Gabriel et al 2008;Girlanda et al 2009;Różalska et al 2010;Krupiński et al 2013), little is known about the proteomic background of these processes. In the current work, the 4-n-NP biodegradation pathway in the filamentous fungus, Metarhizium robertsii, which leads to the complete removal of the xenobiotic through consecutive oxidations of the alkyl chain followed by aromatic ring oxidation and the initial proteome background of 4-n-NP removal, was described.…”

Role of P450 Monooxygenases in the Degradation of the Endocrine-Disrupting Chemical Nonylphenol by the White Rot Fungus Phanerochaete chrysosporium

“…Recent studies have shown the abilities of selected fungi, including white rot fungi, to degrade this chemical, albeit to various extents (33). Extracellular oxidases (laccases) have been implicated in the fungal oxidation of NP (2,19).…”