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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

Time course of PSS depolymerisation by whole cells G. trabeum DSM 1398.Cultures in regular Wetzstein medium (■) were compared to those supplemented with 500 μM 2,5-DMBQ (▲), without iron (♦), and cultures inactivated by sodium azide (control; ●). Symbols represent means ± standard deviations for triplicate cultures; standard deviations smaller than symbol size are not shown.
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pone.0131773.g002: Time course of PSS depolymerisation by whole cells G. trabeum DSM 1398.Cultures in regular Wetzstein medium (■) were compared to those supplemented with 500 μM 2,5-DMBQ (▲), without iron (♦), and cultures inactivated by sodium azide (control; ●). Symbols represent means ± standard deviations for triplicate cultures; standard deviations smaller than symbol size are not shown.

Mentions: Past research on Fenton chemistry-based degradative mechanisms of brown-rot fungi has yielded insight into various factors such as the presence of additional hydroquinones or mannitol, which either enhance or reduce their activity [24,27]. Several related conditions were tested with G. trabeum DSM 1398 in order to substantiate whether Fenton chemistry is operative during PSS depolymerisation by brown-rot fungi. Table 1 depicts the effects of these conditions on the molecular mass of PSS remaining after 20 days in liquid culture relative to the controls. The presence of the iron chelator oxalate, the known hydroxyl radical scavenger mannitol, as well as the omission of 20 μM FeSO4 from Wetzstein medium severely inhibited PSS depolymerisation. In contrast to these observations, the addition of 500 μM 2,5-dimethoxy-1,4-benzoquinone (2,5-DMBQ), naturally employed by Gloeophyllum to drive its Fenton chemistry [41], significantly speeded up PSS depolymerisation as depicted in Fig 2. To a lesser extent, it also reduced the final molecular mass of PSS fragments compared to non-supplemented cultures.


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)

Time course of PSS depolymerisation by whole cells G. trabeum DSM 1398.Cultures in regular Wetzstein medium (■) were compared to those supplemented with 500 μM 2,5-DMBQ (▲), without iron (♦), and cultures inactivated by sodium azide (control; ●). Symbols represent means ± standard deviations for triplicate cultures; standard deviations smaller than symbol size are not shown.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0131773.g002: Time course of PSS depolymerisation by whole cells G. trabeum DSM 1398.Cultures in regular Wetzstein medium (■) were compared to those supplemented with 500 μM 2,5-DMBQ (▲), without iron (♦), and cultures inactivated by sodium azide (control; ●). Symbols represent means ± standard deviations for triplicate cultures; standard deviations smaller than symbol size are not shown.
Mentions: Past research on Fenton chemistry-based degradative mechanisms of brown-rot fungi has yielded insight into various factors such as the presence of additional hydroquinones or mannitol, which either enhance or reduce their activity [24,27]. Several related conditions were tested with G. trabeum DSM 1398 in order to substantiate whether Fenton chemistry is operative during PSS depolymerisation by brown-rot fungi. Table 1 depicts the effects of these conditions on the molecular mass of PSS remaining after 20 days in liquid culture relative to the controls. The presence of the iron chelator oxalate, the known hydroxyl radical scavenger mannitol, as well as the omission of 20 μM FeSO4 from Wetzstein medium severely inhibited PSS depolymerisation. In contrast to these observations, the addition of 500 μM 2,5-dimethoxy-1,4-benzoquinone (2,5-DMBQ), naturally employed by Gloeophyllum to drive its Fenton chemistry [41], significantly speeded up PSS depolymerisation as depicted in Fig 2. To a lesser extent, it also reduced the final molecular mass of PSS fragments compared to non-supplemented cultures.

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