SEC elution profiles of samples from culture supernatants.

<p>Samples were taken over the course of incubation of a single representative <i>G</i>. <i>trabeum</i> culture containing ultrafiltrated PSS in regular Wetzstein medium. Samples from the start of cultivation ( — ), and from culture day 7 ( - - ), 14 (∙ ∙ ∙), and 20 ( - ∙ - ) were analysed.</p

Hydroxyl radical generation by <i>G</i>. <i>trabeum</i> under varied culture conditions.

<p>Production of TBARS from 2-deoxyribose monitored at 530 nm was used as an indicator. Conditions shown: culture in regular Wetzstein medium (■); azide-inactivated (●); no iron (♦); quinone-supplemented (▲). Symbols represent means ± standard deviation for triplicate cultures; standard deviations smaller than symbol size are not shown.</p

Concentration of 2,5-DMBQ in supernatants of actively depolymerising <i>G</i>. <i>trabeum</i> cultures in regular Wetzstein medium.

<p>Symbols represent means ± standard deviation of triplicate cultures.</p

Time course of PSS depolymerisation by whole cells <i>G</i>. <i>trabeum</i> DSM 1398.

<p>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.</p

Total ion current chromatogram of the extract obtained from culture supernatant.

<p>The sample was taken from a regular culture after 10 days of incubation. The magnified sector indicates the 2,5-DMHQ (no. 1) and the 2,5-DMHQ monoacetate (no. 2) as well as the inferred 2,5-DMBQ (*). The signal no. 3 has the molecular mass 190 g/mol.</p

Molecular masses of PSS after fungal treatment for 20 days.

<p>Grey: M_n; white: M_w. Corresponding controls were inactivated with sodium azide. Bars represent means ± standard deviation for triplicate cultures.</p

Effect of varied conditions on PSS depolymerisation by <i>G</i>. <i>trabeum</i>

<p>.</p

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

<div><p>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 (M_n) within 20 days. In-depth investigations with the most efficient depolymeriser, a <i>Gloeophyllum trabeum</i> 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 <i>G</i>. <i>trabeum</i> cultures. Up to 80% reduction in M_n 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 <i>Trametes versicolor</i> 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.</p></div