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Potential of Wood-Rotting Fungi to Attack Polystyrene Sulfonate and Its Depolymerisation by Gloeophyllum trabeum via Hydroquinone-Driven Fenton Chemistry.

Krueger MC, Hofmann U, Moeder M, Schlosser D - PLoS ONE (2015)

Bottom Line: Up to 80% reduction in Mn of PSS where observed when fungal cultures were additionally supplemented with 2,5-dimethoxy benzoquinone, the oxidized from of 2,5-DMHQ.In contrast, white-rot fungi were unable to cause substantial depolymerising effects despite the expression of lignin-modifying exo-enzymes.Our results indicate that brown-rot fungi might be suitable organisms for the biodegradation of recalcitrant synthetic polymeric pollutants.

View Article: PubMed Central - PubMed

Affiliation: Department Environmental Microbiology, Helmholtz Centre for Environmental Research-UFZ, Leipzig, Germany.

ABSTRACT
Synthetic polymers often pose environmental hazards due to low biodegradation rates and resulting accumulation. In this study, a selection of wood-rotting fungi representing different lignocellulose decay types was screened for oxidative biodegradation of the polymer polystyrene sulfonate (PSS). Brown-rot basidiomycetes showed PSS depolymerisation of up to 50 % reduction in number-average molecular mass (Mn) within 20 days. In-depth investigations with the most efficient depolymeriser, a Gloeophyllum trabeum strain, pointed at extracellular hydroquinone-driven Fenton chemistry responsible for depolymerisation. Detection of hydroxyl radicals present in the culture supernatants showed good compliance with depolymerisation over the time course of PSS degradation. 2,5-Dimethoxy-1,4-hydroquinone (2,5-DMHQ), which was detected in supernatants of active cultures via liquid chromatography and mass spectrometry, was demonstrated to drive the Fenton processes in G. trabeum cultures. Up to 80% reduction in Mn of PSS where observed when fungal cultures were additionally supplemented with 2,5-dimethoxy benzoquinone, the oxidized from of 2,5-DMHQ. Furthermore, 2,5-DMHQ could initiate the Fenton's reagent-mediated PSS depolymerisation in cell-free systems. In contrast, white-rot fungi were unable to cause substantial depolymerising effects despite the expression of lignin-modifying exo-enzymes. Detailed investigations with laccase from Trametes versicolor revealed that only in presence of certain redox mediators limited PSS depolymerisation occurred. Our results indicate that brown-rot fungi might be suitable organisms for the biodegradation of recalcitrant synthetic polymeric pollutants.

No MeSH data available.


Related in: MedlinePlus

Concentration of 2,5-DMBQ in supernatants of actively depolymerising G. trabeum cultures in regular Wetzstein medium.Symbols represent means ± standard deviation of triplicate cultures.
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pone.0131773.g005: Concentration of 2,5-DMBQ in supernatants of actively depolymerising G. trabeum cultures in regular Wetzstein medium.Symbols represent means ± standard deviation of triplicate cultures.

Mentions: Fungal production of quinones potentially contributing to extracellular Fenton chemistry in G. trabeum [27,41] was evidenced by analysis of fungal culture supernatants, using UPLC coupled to UV/vis detection where 2,5-DMBQ shows a much stronger absorption in the UV range than 2,5-DMHQ does. 2,5-DMBQ present in fungal culture supernatants eluted around 0.44–0.45 min (authentic 2,5-DMBQ used as a standard: 0.445 min) and produced a distinct peak in the chromatograms. The UV/vis spectrum of this peak was in good agreement with authentic 2,5-DMBQ standards (maximum absorbance for both compounds at approximately 282 nm). In Fig 5, the development of 2,5-DMBQ concentration over the time course of a cultivation in regular Wetzstein medium is shown. 2,5-DMBQ concentration increased during the first half of cultivation and slightly declined thereafter. 2,5-DMHQ could not be detected in any sample via UPLC, most likely due to its relatively weak absorbance. However, after extraction of the aqueous samples and enrichment of the analytes, 2,5-DMHQ could be detected by GC-MS. The GC-MS analysis of an extract prepared from a sample after 10 days of incubation provided the chromatogram shown in Fig 6. The cut in Fig 6 exhibits the magnified region of the chromatogram indicating the 2,5-DMHQ (signal no.1) and the monoacetate of 2,5-DMHQ (no.2), which is formed during the fungal treatment. The structure of the monoacetylated 2,5-DMHQ was proven by a synthesised reference compound. The corresponding mass spectra and GC-MS data are presented in the S1 File. 2,5-DMBQ („*”in Fig 6) seems to co-elute with 2,5-DMHQ monoacetate but due to the inferred mass spectra, an unambiguous identification in full scan mode was difficult.


Potential of Wood-Rotting Fungi to Attack Polystyrene Sulfonate and Its Depolymerisation by Gloeophyllum trabeum via Hydroquinone-Driven Fenton Chemistry.

Krueger MC, Hofmann U, Moeder M, Schlosser D - PLoS ONE (2015)

Concentration of 2,5-DMBQ in supernatants of actively depolymerising G. trabeum cultures in regular Wetzstein medium.Symbols represent means ± standard deviation of triplicate cultures.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4493105&req=5

pone.0131773.g005: Concentration of 2,5-DMBQ in supernatants of actively depolymerising G. trabeum cultures in regular Wetzstein medium.Symbols represent means ± standard deviation of triplicate cultures.
Mentions: Fungal production of quinones potentially contributing to extracellular Fenton chemistry in G. trabeum [27,41] was evidenced by analysis of fungal culture supernatants, using UPLC coupled to UV/vis detection where 2,5-DMBQ shows a much stronger absorption in the UV range than 2,5-DMHQ does. 2,5-DMBQ present in fungal culture supernatants eluted around 0.44–0.45 min (authentic 2,5-DMBQ used as a standard: 0.445 min) and produced a distinct peak in the chromatograms. The UV/vis spectrum of this peak was in good agreement with authentic 2,5-DMBQ standards (maximum absorbance for both compounds at approximately 282 nm). In Fig 5, the development of 2,5-DMBQ concentration over the time course of a cultivation in regular Wetzstein medium is shown. 2,5-DMBQ concentration increased during the first half of cultivation and slightly declined thereafter. 2,5-DMHQ could not be detected in any sample via UPLC, most likely due to its relatively weak absorbance. However, after extraction of the aqueous samples and enrichment of the analytes, 2,5-DMHQ could be detected by GC-MS. The GC-MS analysis of an extract prepared from a sample after 10 days of incubation provided the chromatogram shown in Fig 6. The cut in Fig 6 exhibits the magnified region of the chromatogram indicating the 2,5-DMHQ (signal no.1) and the monoacetate of 2,5-DMHQ (no.2), which is formed during the fungal treatment. The structure of the monoacetylated 2,5-DMHQ was proven by a synthesised reference compound. The corresponding mass spectra and GC-MS data are presented in the S1 File. 2,5-DMBQ („*”in Fig 6) seems to co-elute with 2,5-DMHQ monoacetate but due to the inferred mass spectra, an unambiguous identification in full scan mode was difficult.

Bottom Line: Up to 80% reduction in Mn of PSS where observed when fungal cultures were additionally supplemented with 2,5-dimethoxy benzoquinone, the oxidized from of 2,5-DMHQ.In contrast, white-rot fungi were unable to cause substantial depolymerising effects despite the expression of lignin-modifying exo-enzymes.Our results indicate that brown-rot fungi might be suitable organisms for the biodegradation of recalcitrant synthetic polymeric pollutants.

View Article: PubMed Central - PubMed

Affiliation: Department Environmental Microbiology, Helmholtz Centre for Environmental Research-UFZ, Leipzig, Germany.

ABSTRACT
Synthetic polymers often pose environmental hazards due to low biodegradation rates and resulting accumulation. In this study, a selection of wood-rotting fungi representing different lignocellulose decay types was screened for oxidative biodegradation of the polymer polystyrene sulfonate (PSS). Brown-rot basidiomycetes showed PSS depolymerisation of up to 50 % reduction in number-average molecular mass (Mn) within 20 days. In-depth investigations with the most efficient depolymeriser, a Gloeophyllum trabeum strain, pointed at extracellular hydroquinone-driven Fenton chemistry responsible for depolymerisation. Detection of hydroxyl radicals present in the culture supernatants showed good compliance with depolymerisation over the time course of PSS degradation. 2,5-Dimethoxy-1,4-hydroquinone (2,5-DMHQ), which was detected in supernatants of active cultures via liquid chromatography and mass spectrometry, was demonstrated to drive the Fenton processes in G. trabeum cultures. Up to 80% reduction in Mn of PSS where observed when fungal cultures were additionally supplemented with 2,5-dimethoxy benzoquinone, the oxidized from of 2,5-DMHQ. Furthermore, 2,5-DMHQ could initiate the Fenton's reagent-mediated PSS depolymerisation in cell-free systems. In contrast, white-rot fungi were unable to cause substantial depolymerising effects despite the expression of lignin-modifying exo-enzymes. Detailed investigations with laccase from Trametes versicolor revealed that only in presence of certain redox mediators limited PSS depolymerisation occurred. Our results indicate that brown-rot fungi might be suitable organisms for the biodegradation of recalcitrant synthetic polymeric pollutants.

No MeSH data available.


Related in: MedlinePlus