Characterization of 2,3,7,8-tetrachlorodibenzo-p-dioxin biodegradation by extracellular lignin-modifying enzymes from ligninolytic fungus

Anh T.N. Dao, Sander J. Loenen, Kees Swart, Ha T.C. Dang, Abraham Brouwer, Tjalf E. de Boer*

*Corresponding author for this work

    Research output: Contribution to JournalArticleAcademicpeer-review

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    Abstract

    Ligninolytic fungi secrete extracellular lignin-modifying enzymes (LME) that degrade plant polymers for fungal nutrition but that are, because of their broad substrate specificity, also applicable for the degradation of many hazardous pollutants. Laccase is one of the most well characterized LME and is involved in the removal and degradation of recalcitrant aromatic compounds with or without the assistance of laccase-mediators. The Ligninolytic fungus Rigidoporus sp. FMD21 can degrade 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) with a half-life of 6.2 days. Using Rigidoporus sp. FMD21 crude extracellular enzyme extract (ExE) that mainly consisted of laccase, 77.4% of 2,3,7,8-TCDD was degraded within 36 days. The degradation rate did not depend on the 2,3,7,8-TCDD concentration in the tested range between 0.005 and 0.5 pgTEQ/μL. 2,3,7,8-TCDD was analysed by DR-CALUX® bioassay and the degradation was confirmed by GC-HRMS. In this study, we found evidence for cleavage of the diaryl ether bond in the 2,3,7,8-TCDD molecule and here we propose a new degradation mechanism in which 3,4-dichlorophenol is the main metabolite of 2,3,7,8-TCDD degradation by FMD21’s ExE. Six laccase-mediators were tested. Three of them 1-hydroxybenzotriazole (HBT), syringaldehyde (Syr) and violuric acid (Vio) showed an equipotent added effect on 2,3,7,8-TCDD degradation by ExE, however only in case of Vio a level of significance was reached. The others showed no effect or negatively impacted degradation. In conclusion, we have shown that Rigidoporus sp. FMD21 produces extracellular enzymes, mainly laccases that apparently are able to degrade the highly recalcitrant and most toxic 2,3,7,8-congener of TCDD via diaryl bond cleavage into 3,4-dichlorophenol.

    Original languageEnglish
    Article number128280
    Pages (from-to)1-10
    Number of pages10
    JournalChemosphere
    Volume263
    Early online date12 Sept 2020
    DOIs
    Publication statusPublished - Jan 2021

    Funding

    This work is supported by a BE-Basic Foundation grant from the Ministry of Economic Affairs from the Netherlands and by a grant from the project (code 826/QD-BKHCN, DTDLCN 13/14) of Ministry of Science & Technology Vietnam ( MOST ). The authors would like to thank to Thierry K.S. Janssens for all his help in the early stages of this research.

    FundersFunder number
    Ministry of Science & Technology Vietnam
    Ministry of Science and Technology
    Ministerie van Economische ZakenDTDLCN 13/14
    Ministry of Science and Technology, Taiwan
    BE-Basic Foundation

      Keywords

      • 2,3,7,8-Tetrachlorodibenzo-p-dioxin
      • Fungal biodegradation
      • Laccase
      • Laccase-mediators
      • Lignin-modifying enzymes
      • Ligninolytic fungi

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