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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

SEC elution profiles of samples from culture supernatants.Samples were taken over the course of incubation of a single representative G. trabeum culture containing ultrafiltrated PSS in regular Wetzstein medium. Samples from the start of cultivation ( — ), and from culture day 7 ( - - ), 14 (∙ ∙ ∙), and 20 ( - ∙ - ) were analysed.
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pone.0131773.g003: SEC elution profiles of samples from culture supernatants.Samples were taken over the course of incubation of a single representative G. trabeum culture containing ultrafiltrated PSS in regular Wetzstein medium. Samples from the start of cultivation ( — ), and from culture day 7 ( - - ), 14 (∙ ∙ ∙), and 20 ( - ∙ - ) were analysed.

Mentions: Further insight into the depolymerisation mechanism was gained from comparisons of SEC chromatograms recorded at different times of cultivation (Fig 3). With increasing time, the peak corresponding to the major PSS fraction continuously moved to longer retention times indicating lower molecular masses. Concomitantly, two new peaks with intensities increasing over time appeared at retention times in the range of mono- and dimeric compounds (i.e. approximately 200 and 400 Da). The increase in intensities of these peaks apparently was a continuous process (S1 Fig). Unfortunately, certain fractions of the partially degraded PSS showed a considerably higher absorbance than the undegraded polymer at around 250 nm, which hampered a direct comparison and quantification (compare especially S2A and S2B Fig).


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)

SEC elution profiles of samples from culture supernatants.Samples were taken over the course of incubation of a single representative G. trabeum culture containing ultrafiltrated PSS in regular Wetzstein medium. Samples from the start of cultivation ( — ), and from culture day 7 ( - - ), 14 (∙ ∙ ∙), and 20 ( - ∙ - ) were analysed.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0131773.g003: SEC elution profiles of samples from culture supernatants.Samples were taken over the course of incubation of a single representative G. trabeum culture containing ultrafiltrated PSS in regular Wetzstein medium. Samples from the start of cultivation ( — ), and from culture day 7 ( - - ), 14 (∙ ∙ ∙), and 20 ( - ∙ - ) were analysed.
Mentions: Further insight into the depolymerisation mechanism was gained from comparisons of SEC chromatograms recorded at different times of cultivation (Fig 3). With increasing time, the peak corresponding to the major PSS fraction continuously moved to longer retention times indicating lower molecular masses. Concomitantly, two new peaks with intensities increasing over time appeared at retention times in the range of mono- and dimeric compounds (i.e. approximately 200 and 400 Da). The increase in intensities of these peaks apparently was a continuous process (S1 Fig). Unfortunately, certain fractions of the partially degraded PSS showed a considerably higher absorbance than the undegraded polymer at around 250 nm, which hampered a direct comparison and quantification (compare especially S2A and S2B Fig).

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