Degradation of bisphenol A by different fungal laccases and identification of its degradation products

29 p.-5 fig.Different fungal laccases were used as biocatalysts for the biotransformation of bisphenol A (BPA). The quantitative analysis by gas chromatography-mass spectrometry (GCeMS) showed that BPA is more rapidly oxidized by Coriolopsis gallica laccase among the different fungal laccases tested. Carboxylic acid derivatives such as tartaric acid was found as BPA degradation products resulting from reactions catalyzed by 1 U ml 1 of laccase from C. gallica in the presence of 1 mM of the laccase-mediator 1-hydroxybenzotriazole (HBT), while b-hydroxybutyric acid resulted from oxidative reactions without HBT. BPA was completely removed within 3 h and pyroglutamic acid was found as a supplementary oxidative degradation product from HBT when identified by GCeMS. Laccase played a critical role in BPA biodegradation and catalyzed a cross-coupling reactionThis work was supported by the Ministry of Higher Education, Scientific Research (Tunisia) and the Comunidad de Madrid project S2013/MAE-2907Peer reviewe

Phylogenetic and metabolic diversity of Tunisian forest wood-degrading fungi: a wealth of novelties and opportunities for biotechnology

16 p.-2 fig.-5 tab.In this study, 51 fungal strains were isolated from decaying wood samples collected from forests located in the Northwest of Tunisia in the vicinity of Bousalem, Ain Draham and Kef. Phylogenetic analysis based on the sequences of the internal transcribed spacers of the ribosomal DNA showed a high diversity among the 51 fungal isolates collection. Representatives of 25 genera and 29 species were identified, most of which were members of one of the following phyla (Ascomycota, Basidiomycota and Zygomycota). In addition to the phylogenetic diversity, a high diversity of secreted enzyme profiles was also detected among the fungal isolates. All fungal strains produced at least one of the following enzymes: laccase, cellulase, protease and/or lipase.This project received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under Grant Agreement No. 245268 (to L.B.). This study was also supported by the SwissBOL project, financed by the Swiss Federal Office for the Environment (Grant holder L.B.), the Swiss State Secretariat for Education and Research (L.B. Grant Reference: SER No. C09.0139), and the European Union for the COST action FP0801 ‘‘Established and Emerging Phytophthora: Increasing Threats to Woodland and Forest Ecosystems in Europe’’.Peer reviewe

Autochthonous fungal strains with high ligninolytic activities from Tunisian biotopes

6 p.-2 tab.-3 fig.This work represents the first report on the ability of autochthonous fungi of Tunisia to produce ligninolytic enzymes. Three hundred fifteen fungal strains were isolated from different Tunisian biotopes. These fungal strains were first screened for lignin-modifying enzymes on solid media containing Poly R-478 or ABTS. Of the 315 tested strains, 49 exhibited significant ABTS-oxidation activity, expressed within the first week of incubation and only 18 strains decolourised the Poly R-478. These positive strains were further screened in liquid culture and laccase, and lignin and Mn2+-oxidizing peroxidases activities were assayed. Of the 67 strains grown on liquid medium, 28 produced at least one of these 3 enzymes. The 8 highest producers of ligninolytic activities were identified by molecular techniques and 3 among them produced Lac, MnP and LiP simultaneously. New isolates reported in this work as fungi with significant ligninolytic activities includes Oxyporus, Stereum and Trichoderma. The isolated Trametes trogii CTM 10156 was the best Lac producer. Culture conditions and medium composition were optimised for this strain and resulted in high Lac production of 110 U ml-1 within 15 days of incubation (367 times higher than control medium).This research was supported by EU contract N° ICA3-CT-1999-00010 and “Contrats Programmes SERST, Tunisia.Peer reviewe

Autochthonous fungal strains with high ligninolytic activities from Tunisian biotopes

This work represents the first report on the ability of autochthonous fungi of Tunisia to produce ligninolytic enzymes. Three hundred fifteen fungal strains were isolated from different Tunisian biotopes. These fungal strains were first screened for lignin-modifying enzymes on solid media containing Poly R-478 or ABTS. Of the 315 tested strains, 49 exhibited significant ABTS-oxidation activity, expressed within the first week of incubation and only 18 strains decolourised the Poly R-478. These positive strains were further screened in liquid culture and laccase, and lignin and Mn2+-oxidizing peroxidases activities were assayed. Of the 67 strains grown on liquid medium, 28 produced at least one of these 3 enzymes. The 8 highest producers of ligninolytic activities were identified by molecular techniques and 3 among them produced Lac, MnP and LiP simultaneously. New isolates reported in this work as fungi with significant ligninolytic activities includes Oxyporus, Stereum and Trichoderma. The isolated Trametes trogii CTM 10156 was the best Lac producer. Culture conditions and medium composition were optimised for this strain and resulted in high Lac production of 110 U ml-1 within 15 days of incubation (367 times higher than control medium).African Journal of Biotechnology Vol. 4 (5), pp. 431-436, 200

Modelling of Reactive Black 5 decolourization in the presence of heavy metals by the newly isolated Pseudomonas aeruginosa strain Gb30

Acknowledgements This work was supported by the Ministry of Higher Education and Scientific Research of Tunisia.Peer reviewedPostprin

Simultaneous cleanup of Reactive Black 5 and cadmium by a desert soil bacterium

This work was supported by the Ministry of Higher Education and Scientific Research of Tunisia. Special thanks to the Materials Engineering Department of the National School of Engineers of Sfax for help in FTIR spectroscopy analysis and the Digital Research Center of Sfax (CRNS) for support in AFM spectroscopy.Peer reviewedPostprin

Anaerobic degradation of methoxylated aromatic compounds by Clostridium methoxybenzovorans and a nitrate-reducing bacterium Thauera sp. strain Cin3,4

The coupling of growth of the o-demethylating bacterium, Clostridium methoxybenzovorans SR3, with a nitrate-reducing bacterium able to degrade aromatic compounds, Thauera sp. Cin3,4, allowed complete mineralization of poorly oxidizable methoxylated aromatic compounds such as vanillate, isovanillate, vanilline, anisate, ferulate and veratrate. C. methoxybenzovorans o-demethylated these aromatic compounds to their corresponding hydroxylated derivatives and fermented the side chains to acetate and butyrate. The hydroxylated compounds and the fermentation end-products in the C. methoxybenzovorans spent growth medium were then completely metabolized to CO2 on inoculation with the Thauera strain. Kinetic studies with veratrate indicated that C. methoxybenzovorans initially o-demethylated the substrate to vanillate and then further to protocatechuate together with the production of acetate and butyrate from the demethylated side chains. Protocatechuate, acetate and butyrate were then utilized as a carbon source by the Thauera strain aerobically or anaerobically in the presence of nitrate. The results therefore suggest that mono- or dimethoxylated aromatic compounds can be completely mineralized by coupling the growth of a fermentative bacterium with a nitrate-reducing bacterium, and a metabolic pathway for this is proposed

Decolorization of the azo dye Acid Orange 51 by laccase produced in solid culture of a newly isolated Trametes trogii strain

11 p.-5 fig.-6 tab.This study concerns the decolorization and detoxification of the azo dye Acid Orange 51 (AO51) by crude laccase from Trametes trogii produced in solid culture using sawdust as support media. A three-level Box–Behnken factorial design with four factors (enzyme concentration, 1-hydroxybenzotriazole (HBT) concentration, dye concentration and reaction time) combined with response surface methodology was applied to optimize AO51 decolorization. A mathematical model was developed showing the effect of each factor and their interactions on color removal. The model predicted that Acid Orange 51 decolorization above 87.87 ± 1.27 % could be obtained when enzyme concentration, HBT concentration, dye concentration and reaction time were set at 1 U/mL, 0.75 mM, 60 mg/L and 2 days, respectively. The experimental values were in good agreement with the predicted ones and the models were highly significant, the correlation coefficient (R 2) being 0.9. Then the desirability function was employed to determine the optimal decolorization condition for each dye and minimize the process cost simultaneously. In addition, germination index assay showed that laccase-treated dye was detoxified; however in the presence of HBT, the phytotoxicity of the treated dye was increased. By using cheap agro-industrial wastes, such as sawdust, a potential laccase was obtained. The low cost of laccase production may further broaden its application in textile wastewater treatment.Peer reviewe

Isolation and characterization of a mesophilic heavy-metals-tolerant sulfate-reducing bacterium Desulfomicrobium sp. from an enrichment culture using phosphogypsum as a sulfate source

A sulfate-reducing bacterium, was isolated from a 6 month trained enrichment culture in an anaerobic media containing phosphogypsum as a sulfate source, and, designated strain SA2. Cells of strain SA2 were rod-shaped, did not form spores and stained Gram-negative. Phylogenetic analysis of the 16S rRNA gene sequence of the isolate revealed that it was related to members of the genus Desulfomicrobium (average sequence similarity of 98%) with Desulfomicrobium baculatum being the most closely related (sequence similarity of 99%). Strain SA2 used thiosulfate, sulfate, sulfite and elemental sulfur as electron acceptors and produced sulfide. Strain SA2 reduced sulfate contained in 1–20 g/L phosphogypsum to sulfide with reduction of sulfate contained in 2 g/L phosphogypsum being the optimum concentration. Strain SA2 grew with metalloid, halogenated and non-metal ions present in phosphogypsum and with added high concentrations of heavy metals (125 ppm Zn and 100 ppm Ni, W, Li and Al). The relative order for the inhibitory metal concentrations, based on the IC50 values, was Cu, Te > Cd > Fe, Co, Mn > F, Se > Ni, Al, Li > Zn

Laccase purification and characterization from Trametes trogii isolated in Tunisia: decolorization of textile dyes by the purified enzyme

8 páginas, 3 figuras, 5 tablas -- PAGS nros. 141-148A white-rot basidiomycete, isolated from decayed acacia wood (from Northwest of Tunisia) and identified as Trametes trogii, was selected in a broad plate screening because of its ability to degrade commercial dyes. In liquid cultures using a glucose–peptone medium, the sole ligninolytic activity detected was laccase. The highest laccase levels were obtained in presence of CuSO4 as inducer (around 20000 U/l). Two isoenzymes, were purified using anion-exchange and size-exclusion chromatographies. Both isoenzymes are monomeric proteins, with Mw around 62 kDa and isoelectric points of 4.3 and 4.5, showing similar stability at pH and temperature, optimum pH and substrate specificity. The highest oxidation rate was obtained at pH 2 and 2.5 for ABTS and DMP, respectively. They were stable up to 50 °C for 24 h and the stability was higher at alkaline pH. Activity increased by the addition of 10 mM Ni, Mo or Mn but it was not affected by Cd, Al, Li and Ca. Identical N-terminal sequences were determined in both laccases. The crude enzyme, as well as the purified laccase, was able to decolorize dyes from the textile industryThis research has been funded by a Cooperation project between Spain and Tunisia (31p/02 – Spanish “Ministerio de Asuntos Exteriores” and “MRSTDC”), and in part by a grant from “Contrats Programmes MRSTCD” (Tunisia)Peer reviewe