Resumo A resistência à degradação de chapas de madeira-plástico aos fungos de podridão-branca, Trametes versicolor (Linnaeus ex Fries) Pilát, e de podridão-parda, Gloeophyllum trabeum (Persoon ex ...Fries) Murrill, foi avaliada conforme a norma ASTM D 2017-81 (1994). As chapas foram confeccionadas com cavacos de Eucalyptus grandis e pellets de polietileno de baixa densidade (PEBD) pós-consumo nas proporções de plástico/madeira de 40/60, 50/50, 60/40 e 100/0. Utilizou-se como testemunha a madeira de E. grandis. Houve maior ataque do fungo de podridão-parda em relação ao fungo de podridão-branca. Foi observada correlação negativa entre o teor de plástico e o grau de ataque de ambos os fungos. De modo geral, as chapas de madeira-plástico foram classificadas como “altamente resistente” com exceção da proporção com 40% de plástico, que foi classificada como “resistente” ao ataque do fungo de podridão-parda. O índice de susceptibilidade de degradação (DSI) calculado, que leva em conta a densidade do material e a perda de massa real, mostrou que os compósitos foram mais resistentes que a madeira utilizada como referência.
We studied the influence of an immobilized laccase from Trametes versicolor on non-extractable residue (NER) formation of the systemic fungicide super(14)C-metalaxyl in soil. We added the enzyme (130 ...mU/g DW) to soil sterilized by gamma irradiation and observed that the amount of NER (6.3 % of applied radioactivity) after 10 days of incubation was enhanced about twofold compared to the sterile soil without laccase addition. Residues formed within samples without enhanced enzyme activity were mainly bound via ester linkages to all fractions of humic matter, i.e., fulvic acids, humic acids, non-humines, and humines, respectively. In contrast, residues formed in presence of immobilized laccase were more strongly bound by covalent linkages such as ether and C-C bonds, especially to humic acids. After chemical degradation of the humic matter, it could be observed that all NER contained the first major transformation product, i.e., metalaxyl acid. The findings underline that the residue formation of metalaxyl in soil may be partly catalyzed by immobilized extracellular oxidative enzymes through oxidative coupling reactions within the humic matter.
High potential multicopper oxidases (MCOs) have T1 reduction potentials >600 mV (vs normal hydrogen electrode), making them important catalysts for O2 reduction in various biotechnological ...applications. The oxygen reduction mechanism for the low potential MCOs is well-characterized; however, O2 reactivity of high potential MCOs is not well understood. In this study, we have shown that laccase from Trametes versicolor, where the T1 redox potential is increased by ∼350 mV over that of the low potential MCOs corresponding to an 8 kcal/mol decrease in the driving force, exhibits a slower intramolecular electron transfer (IET) rate to the trinuclear Cu cluster (TNC) in the native intermediate (NI), relative to the low potential MCO from Rhus vernicifera laccase. This IET rate is, however, >102 times faster than the decay rate of the NI, demonstrating that this intermediate form of the enzyme is catalytically relevant enabling fast turnover. However, in contrast to the low potential MCOs where T1 reduction by substrate is rate limiting, the rate limiting step in turnover of high potential MCOs is the first IET to NI. Part of the reduction potential difference of the T1 sites in high vs low potential MCOs is balanced by an ∼100 mV higher reduction potential of NI due to the more positive protein environment in the vicinity of the TNC.
A monomeric 64-kDa laccase from Trametes versicolor IBL-04 was immobilized onto chitosan microspheres using glutaraldehyde as a cross-linking agent. The resulted modified biocatalyst was used for the ...decolorization of textile reactive dyes to explore its potential for industrial and environmental biotechnological applications.
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•Successful immobilization of laccase in chitosan beads by cross-linking approach.•Immobilized laccase with remarkable catalytic and storage stability properties.•Effective decolorization potential against array of Sandal reactive textile dyes.•Enhanced thermal and reusability characteristics of the carrier-supported laccase.
Laccase/mediator systems are promising bio-remediating agents as the rates of reactions can be considerably enhanced in the presence of low molecular weight mediators. A monomeric 64-kDa laccase produced by Trametes versicolor IBL-04 was effectively immobilized onto chitosan microspheres using glutaraldehyde as activating/cross-linking agent. Chitosan beads developed from 2.5% (w/v) chitosan concentration and activated by 1.5% (v/v) glutaraldehyde solution displayed best laccase immobilization efficiency. Scanning electron microscopy showed that beads with encapsulated laccase on the surface were spherical in shape having large surface area. The chitosan beads immobilized laccase (denoted as CTS-Lac) exhibited a broader active pH and temperature range and showed maximum activity at pH 6.0 and 60°C. After immobilization, the affinity of the enzyme toward its substrate increased (Km decreased), leading to enhanced catalytic efficiency (Vmax increased). As compared to free laccase, the CTS-Lac showed significantly improved thermal and storage stability. The catalytic activity of the immobilized laccase was also demonstrated by the decolorization of five different textile reactive dyes. In the presence of 2,2′-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) as redox mediator, a maximum of 100% decolorization was achieved within the shortest time period of 4.0h, indicating the effectiveness of CTS-Lac for the removal of textile dyes from an aqueous solution. It also retained 80.19% of its activity after ten continuous decolorization cycles for Sandal-fix Red C4BLN. The kinetic, thermo-stability and dye-decolorizing characteristics of CTS-Lac/mediator system reflect its potential for use in industrial and environmental biotechnology.
Lignin is a biopolymer found in plant cell walls that accounts for 30% of the organic carbon in the biosphere. White-rot fungi (WRF) are considered the most efficient organisms at degrading lignin in ...nature. While lignin depolymerization by WRF has been extensively studied, the possibility that WRF are able to utilize lignin as a carbon source is still a matter of controversy. Here, we employ
C-isotope labeling, systems biology approaches, and in vitro enzyme assays to demonstrate that two WRF,
and
, funnel carbon from lignin-derived aromatic compounds into central carbon metabolism via intracellular catabolic pathways. These results provide insights into global carbon cycling in soil ecosystems and furthermore establish a foundation for employing WRF in simultaneous lignin depolymerization and bioconversion to bioproducts-a key step toward enabling a sustainable bioeconomy.
An efficient valorization of tea residues into value-added product was developed by Trametes versicolor in solid-state fermentation (SSF). The laccase production of 25.7 U/g dry substrate was ...obtained by optimizing culture medium and condition, resulting in a 4.0-fold increase compared to that of 6.4 U/g dry substrate under unoptimized condition. During the 7-day cultivation under SSF, 44.7%, 12.2% and 9.8% degradation occurred for lignin, hemicellulose and cellulose in tea residues, respectively. Laccase production reached 31.2 U/g dry substrate by the scaling-up culture in shallow tray system. The dry fermented tea residues were directly used as crude enzyme in the decolorization of malachite green. It possessed a decolorization rate of more than 95% within 120 min and remained 81.3% of decolorization capacity after 6 cycles. The present study provided a useful strategy for low-cost laccase production by SSF and it exhibited great potential for the application in dye decolorization.
•Solid-state fermentation of tea residues by T. versicolor provided high laccase production.•Dry fermented tea residue can be used as crude enzyme for dye decolorization directly.•Crude enzyme performed high-efficient dye decolorization and good reusability.
Naturally-occurring phenolic acids (PAs) act as humic precursors that participate in the conversion behaviors and coupling pathways of steroidal estrogens (SEs) during laccase-triggered humification ...processes (L-THPs). Herein, the influences and mechanisms of PAs on Trametes versicolor laccase-evoked 17β-estradiol (E2) conversion kinetics and humification routes were explored. Fungal laccase was fleet in converting > 99% of E2, and the calculated pseudo-first-order velocity constant and half-time values were respectively 0.039 min−1 and 17.906 min. PAs containing an O-dihydroxy moiety such as gallic acid and caffeic acid evidently hampered E2 humification owning to the yielded highly reactive O-quinones reversed E2 radicals by hydrogen transfer mechanism, implying that the inhibition effect was enormously dependent upon the number and position of the phenolic –OH present in humic precursors. Oligomers and polymers with carbon-carbon/oxygen links were tentatively found as E2 main humified species resulting from laccase-evoked successive oxidative-coupling. Note that PAs participating in the humification also encountered oxydehydrogenation, self-polymerization, and cross-binding to E2. Interestingly, the –COOH and –OCH3 groups of PAs could be deprived in radical-caused self/co-polymerization. The generation of humified products not only circumvented the environmental risks of parent compounds but accelerated global carbon sequestration. To our knowledge, this is the first in-depth revelation of the humification pathways and related mechanisms of SEs with humic precursors in aquatic ecosystems by L-THPs.
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•The conversion efficiency of E2 with PA-free reached to 99.24% during L-THPs.•PAs containing an O-dihydroxy moiety reversed E2 radicals via forming O-quinones.•Oligomers/polymers with carbon-carbon/oxygen links were discovered as E2 principal products.•PAs participating in L-THPs encountered oxydehydrogenation, self-coupling, and cross-binding to E2.•Humification routes and mechanisms of E2 with humic precursors in L-THPs were proposed.
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•Novel use of laccase coupled UlS technique to degrade antibiotics in wastewater.•UAL treatment achieved maximum degradation of CTC in lower time.•Degradation rate was increased by ...5.6 folds in UAL treatment.•Laccase at 0.5 U/L removed over 80% of 2 µg/L CTC in 2 h at pH 4.5 by UlS assistance.
Chlortetracycline (CTC) is widely used as a veterinary antibiotic and is considered as a recalcitrant pollutant. In this study, spiked CTC (2 mg L−1) in wastewater was degraded using laccase from the white rot fungi, Trametes Versicolor combined with ultrasonication (UlS). Over 60% of CTC was removed in 2 h by UlS assisted laccase (UAL) treatment where laccase treatment alone took 2 days to degrade 87% of CTC under similar CTC concentration (2 mg L−1), laccase dose (0.5 IU) and pH 6.0 conditions. UAL treatment showed 5.3 folds higher CTC degradation rate compared to laccase alone treatment at pH 6.0. Further, pH optimization of UAL treatment was done and pH 4.5 was found to be optimum wherein 80% of CTC degradation was obtained which is 2.6 folds higher compared to degradation at pH 6.0. The UAL treatment with optimized pH was not only increased CTC degradation efficiency (∼80%) but also reduced the degradation time to 2 h. The obtained results highlighted the enhanced degradation rate, efficiency and unaltered stability of laccase during UAL treatment which can be used for oxidizing other tetracycline groups of antibiotics. Moreover, laccase and UAL treatments showed similar degradation products and no estrogenic activity.
•Chitosan and polyacrylic acid microspheres were designed as carriers for laccase.•A multi-step laccase immobilization procedure with zero length crosslinker was used.•The polyacrylic acid content ...modulated the support and immobilized enzyme properties.•The immobilized product efficiently discolored naphthol green B and indigo carmine.•The immobilization improved the kinetic profile of laccase in dyes decomposition.
Low cost and non-toxic microspheres constituted by different ratios of chitosan (Cs) and polyacrylic acid (PAA) were manufactured as carriers for laccase (Lc). The CsPAA microspheres characterization proved that the PAA content played an important role on the size, surface morphology and rheological properties, and modulated the enzyme immobilization. The immobilization of Lc involved a multi-step procedure in which the 1-ethyl-3-(3-dimethylaminopropyl carbodiimide hydrochloride (EDC) was used as “zero length” crosslinker. The product with the largest active enzyme amount (44.38 mg Lc/g dry support), and the best operational stability profile was 10CsPAALc3. Also, this product contained the lowest PAA concentration and had excellent rheological properties. Moreover, two current hazardous chemicals, indigo carmine (IC) and naphthol green B (NG), were used as model dyes in practical applications. The biocatalytic decomposition of NG and IC was 1.67 and 2.4 times faster for 10CsPAALc3 compared to the free enzyme. The kinetic profile revealed that the immobilized Lc was less prone to substrate, operational and thermal inactivation. For example, the thermal inactivation for 10CsPAALc3 decreased by approximately 25% when dyes were used as substrate and by 11.71% for ABTS, as compared with the free Lc. The recycling test showed that in 5 cycles the immobilized Lc preserves 81% with NG and respectively 72% for IC of initial activity. The results prove that the new immobilized product can be successfully used in indigoid and metal-complex dyes biodegradation.
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