Purification, characterization and decolourization ability of Fomes fomentarius laccase produced in solid medium

Mycelium-Composite Materials-A Promising Alternative to Plastics?

Plastic waste inefficiently recycled poses a major environmental concern attracting attention from both civil society and decision makers. Counteracting the phenomenon is an important challenge today. New possibilities are being explored to find alternatives to plastics, and one of them refers to mycelium-composite materials (MCM). Our study aimed at investigating the possibility of using wood and litter inhabiting basidiomycetes, an underexplored group of fungi that grow fast and create strong mycelial mats, to produce biodegradable materials with valuable properties, using cheap by-products as a substrate for growth. Seventy-five strains have been tested for their ability to grow on low-nutrient media and to form compact mycelial mats. Eight strains were selected further for evaluation on several raw substrates for producing in vitro myco-composites. The physico-mechanical properties of these materials, such as firmness, elasticity and impermeability, were analyzed. Abortiporus biennis RECOSOL73 was selected to obtain, at the laboratory scale, a real biodegradable product. Our results suggest that the strain used is a promising candidate with real possibilities for scalability. Finally, corroborating our results with scientific available data, discussions are being made over the feasibility of such technology, cost-effectiveness, scalability, availability of raw materials and, not least, where future studies should be directed to.

Partial purification and characterization of a thermophilic and alkali-stable laccase of Phoma herbarum isolate KU4 with dye-decolorization efficiency

Production of an extracellular thermophilic and alkali stable laccase from Phoma herbarum isolate KU4 was reported for the first time, both in submerged fermentation (SmF, highest 1590 U/mL) and solid state fermentation (SSF, highest 2014.21 U/mL) using agro-industrial residues. The laccase was partially purified to 7.93 fold with the apparent molecular weight of 298 kDa. The enzyme had pH optimum at 5.0 and temperature optimum at 50 °C, with maximum stability at pH 8.0. It showed activity towards various phenolic and non-phenolic compounds. The kinetic parameters, K_m, V_max and K_cat of the laccase for DMP were 0.216 mM, 270.27 U/mg and 506.69 s^-1, respectively. Laccase activity was inhibited by various metal ions and conventional inhibitors, however, it was slightly increased by Zn²⁺. The laccase showed good decolorization efficiency towards four industrial dyes, namely, methyl violet (75.66%), methyl green (65%), indigo carmine (58%) and neutral red (42%) within 24 h. FTIR analysis of the decolorized products confirmed the degradation of the dyes. The decolorization efficiency of the enzyme suggests that the partially purified laccase could be used to decolorize synthetic dyes present in industrial effluents and for waste water treatments. The thermophilic and alkali stable laccase may also have wider potential industrial applications.

Ligninolytic Enzyme Production and Decolorization Capacity of Synthetic Dyes by Saprotrophic White Rot, Brown Rot, and Litter Decomposing Basidiomycetes

An extensive screening of saprotrophic Basidiomycetes causing white rot (WR), brown rot (BR), or litter decomposition (LD) for the production of laccase and Mn-peroxidase (MnP) and decolorization of the synthetic dyes Orange G and Remazol Brilliant Blue R (RBBR) was performed. The study considered in total 150 strains belonging to 77 species. The aim of this work was to compare the decolorization and ligninolytic capacity among different ecophysiological and taxonomic groups of Basidiomycetes. WR strains decolorized both dyes most efficiently; high decolorization capacity was also found in some LD fungi. The enzyme production was recorded in all three ecophysiology groups, but to a different extent. All WR and LD fungi produced laccase, and the majority of them also produced MnP. The strains belonging to BR lacked decolorization capabilities. None of them produced MnP and the production of laccase was either very low or absent. The most efficient decolorization of both dyes and the highest laccase production was found among the members of the orders Polyporales and Agaricales. The strains with high MnP activity occurred across almost all fungal orders (Polyporales, Agaricales, Hymenochaetales, and Russulales). Synthetic dye decolorization by fungal strains was clearly related to their production of ligninolytic enzymes and both properties were determined by the interaction of their ecophysiology and taxonomy, with a more relevant role of ecophysiology. Our screening revealed 12 strains with high decolorization capacity (9 WR and 3 LD), which could be promising for further biotechnological utilization.

Purification, Biochemical Characterization, and Facile Immobilization of Laccase from Sphingobacterium ksn-11 and its Application in Transformation of Diclofenac

An extracellular laccase enzyme secreted from Sphingobacterium ksn-11 was purified to electrophoretic homogeneity, showing a molecular weight of 90 kDa. The purified enzyme was monomeric in nature confirmed by sodium dodecyl gel electrophoresis. The optimum temperature and pH were found to be 40 °C and 4.5 respectively. The enzyme showed highest substrate specificity for 2,2 azino-bis (ethylthiozoline-6-sulfonate) (ABTS), followed by syringaldazine. The K_m value for ABTS was 2.12 mM with a V_max value of 33.33 U/mg which was higher when compared with syringaldazine and guaiacol substrates. Sodium azide and EDTA inhibited the activity by 30%, whereas presence of Ca²⁺ and iron increased activity by 50%. The purified enzyme was immobilized in sodium alginate-silicon dioxide-polyvinyl alcohol beads and evaluated for diclofenac transformation studies. LC-MS analysis confirmed that immobilized laccase transformed diclofenac to 4-OH diclofenac after 4 h of incubation. 45 % of diclofenac was able to transform even at 3rd cycle of immobilized laccase use. Therefore, immobilized laccase can be used to transform or degrade several recalcitrant compounds from industrial effluents.

Purification and characterization of a fungal laccase from the ascomycete Thielavia sp. and its role in the decolorization of a recalcitrant dye

A laccase-producing ascomycete was isolated from arid soil in Tunisia. This fungus was identified as Thielavia sp. using the phylogenetic analysis of rDNA internal transcribed spacers. The extracellular laccase produced by the fungus was purified to electrophoretic homogeneity, showing a molecular mass around 70 kDa. The enzyme had an optimum pH of 5.0 and 6.0 for ABTS and 2,6‑DMP, respectively and it showed remarkable high thermal stability, showing its optimal temperature at 70 °C (against 2,6‑DMP). It presented slight inhibiting effect by EDTA, SDS and l‑cyst although this effect was more marked by sodium azide (0.1 mM). On the other hand, it showed tolerance to up to 300 mM NaCl, retaining around 50% of its activity at 900 mM. Among the metal ions tested on TaLac1, Mn²⁺ showed an activating effect. Their kinetic parameters K_m and k_cat were 23.7 μM and 4.14 s^-1 for ABTS, and 24.3 μM and 3.46 s^-1 towards 2,6‑DMP. The purified enzyme displayed greater efficiency in Remazol Brilliant Blue R decolorization (90%) in absence of redox mediator, an important property for biotechnological applications.

Isolation, identification of a laccase-producing fungal strain and enzymatic properties of the laccase

A new type of thermostable laccase was isolated from Paraphoma sp. GZS18, and its partial enzymatic properties were determined. A strain GZS18 of laccase with high yield was screened from forest soil and identified as Paraphoma sp. GZS18 through morphological characteristics and ITS sequence analysis. The laccase of Paraphoma sp. GZS18 (Lac-P) was obtained through cation-anion exchange chromatography, gel filtration chromatography, and other purification processes. The testing result shows that Lac-P is a single protein of 75 kDa, and the 11 amino acid sequences in the N-terminal are AX^aVSVASREMT (X^a was the non-standard protein). The optimum temperature and optimum pH of lac-P activity are substrate-independent. The temperature is in the range of 50-70 °C, and pH has high catalytic efficiency in the acidic range. Lac-P has good stability in the temperature and pH. The half time at 70-60 °C is 1.5 and 4 h, respectively. At pH 6-9 and room temperature, there is more than 80% activity 24 h later. Lac-P is tolerant of most metal ions and low concentrations of inhibitors but is inhibited by Hg²⁺, Fe²⁺ and NaN₃. The laccase from Paraphoma sp. GZS18 at high temperature and pH 6-9, with strong stability, has better industrial application characteristics.

Preparation and Optimisation of Cross-Linked Enzyme Aggregates Using Native Isolate White Rot Fungi Trametes versicolor and Fomes fomentarius for the Decolourisation of Synthetic Dyes

The key to obtaining an optimum performance of an enzyme is often a question of devising a suitable enzyme and optimisation of conditions for its immobilization. In this study, laccases from the native isolates of white rot fungi Fomes fomentarius and/or Trametes versicolor, obtained from Czech forests, were used. From these, cross-linked enzyme aggregates (CLEA) were prepared and characterised when the experimental conditions were optimized. Based on the optimization steps, saturated ammonium sulphate solution (75 wt.%) was used as the precipitating agent, and different concentrations of glutaraldehyde as a cross-linking agent were investigated. CLEA aggregates formed under the optimal conditions showed higher catalytic efficiency and stabilities (thermal, pH, and storage, against denaturation) as well as high reusability compared to free laccase for both fungal strains. The best concentration of glutaraldehyde seemed to be 50 mM and higher efficiency of cross-linking was observed at a low temperature 4 °C. An insignificant increase in optimum pH for CLEA laccases with respect to free laccases for both fungi was observed. The results show that the optimum temperature for both free laccase and CLEA laccase was 35 °C for T. versicolor and 30 °C for F. fomentarius. The CLEAs retained 80% of their initial activity for Trametes and 74% for Fomes after 70 days of cultivation. Prepared cross-linked enzyme aggregates were also investigated for their decolourisation activity on malachite green, bromothymol blue, and methyl red dyes. Immobilised CLEA laccase from Trametes versicolor showed 95% decolourisation potential and CLEA from Fomes fomentarius demonstrated 90% decolourisation efficiency within 10 h for all dyes used. These results suggest that these CLEAs have promising potential in dye decolourisation.

A halotolerant laccase from Chaetomium strain isolated from desert soil and its ability for dye decolourization

A novel fungal laccase produced by the ascomycete Chaetomium sp. isolated from arid soil was purified and characterized and its ability to remove dyes was determined. Extracellular laccase was purified 15-fold from the crude culture to homogeneity with an overall yield of 50% using ultrafiltration and anion-exchange chromatography. The purified enzyme was found to be a monomeric protein with a molecular mass of 68 kDa, estimated by SDS-PAGE, and with an isoelectric point of 5.5. The optimal temperature and pH value for laccase activity toward 2,6-DMP were 60 °C and 3.0, respectively. It was stable at temperatures below 50 °C and at alkaline conditions. Kinetic study showed that this laccase showed higher affinity on ABTS than on 2,6-DMP. Its activity was enhanced by the presence of several metal ions such as Mg2+, Ca2+ and Zn2+, while it was strongly inhibited by Fe2+, Ag+ and Hg2+. The novel laccase also showed high, remarkable sodium chloride tolerance. Its ability to decolorize different dyes, with or without HBT (1-hydroxy-benzotriazole), as redox mediator, suggests that this protein may be useful for different industrial applications and/or bioremediation processes.

Purification and characterization of a novel laccase from Fomitopsis pinicola mycelia

A novel laccase was isolated from the culture filtrate of the brown-rot fungus, Fomitopsis pinicola. Enzyme production reached its highest level after cultivation for 8 days at 25°C. The enzyme was purified by ultrafiltration, ion exchange chromatography, gelfiltration chromatography, and hydrophobic interaction chromatography. Zymography analysis of the purified enzyme showed a laccase band with a molecular mass of 92 kDa. The molecular weight of the enzyme was 92 kDa as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and gel filtration chromatography. The enzyme also had an isoelectric point of 3.8. The optimum temperature and pH for enzyme activity were 80°C and 3.0, respectively. Enzyme activity was relatively stable in the pH range from 1.5 to 11.0 and at temperatures below 40°C. The N-terminal amino acid sequence of the enzyme was DTHKAEIACRFKDLG. Enzyme activity was potently inhibited by NaN3 and SDS. The enzyme showed the highest specific activity for 2,2-azino-bis(3-ethylthiazoline-6-sulfonate) (ABTS) as a substrate. The Km value of the enzyme for ABTS substrate was 0.28 mM with a Vmax value of 4.5 U/min. The enzyme degraded several recalcitrant dyes at different time intervals during decolorization. Therefore, the novel laccase from F. pinicola may be potentially useful in industry.

Purification and biochemical characterization of a new alkali-stable laccase from Trametes sp. isolated in Tunisia: role of the enzyme in olive mill waste water treatment

A white-rot basidiomycete, isolated from decayed acacia wood (from Northwest of Tunisia) and identified as Trametes sp, was selected in a broad plate screening because of its ability to decolorize and dephenolize olive oil mill wastewater (OMW) efficiently. The major laccase was purified and characterized as a monomeric protein with apparent molecular mass of 61 kDa (SDS-PAGE). It exhibits high enzyme activity over broad pH and temperature ranges with optimum activity at pH 4.0 and a temperature of 60 °C. The purified laccase is stable at alkaline pH values. The enzyme retained 50 % of its activity after 90 min of incubation at 55 °C. Using ABTS, this laccase presented K m and V max values of 0.05 mM and 212.73 μmoL min(-1) mg(-1), respectively. It has shown a degrading activity towards a variety of phenolic compounds. The purified laccase was partially inhibited by Fe(2+), Zn(2+), Cd(2+) and Mn(2+), while Cu(2+) acted as inducer. EDTA (10 mM) and NaN3 (10 mM) were found to completely inhibit its activity. 73 % OMW was dephenolized after 315 min incubation at 30 °C with 2 U mL(-1) of laccase and 2 mM HBT.

Extracellular enzymes of the white-rot fungus Fomes fomentarius and purification of 1,4-β-glucosidase

Production of the lignocellulose-degrading enzymes endo-1,4-β-glucanase, 1,4-β-glucosidase, cellobiohydrolase, endo-1,4-β-xylanase, 1,4-β-xylosidase, Mn peroxidase, and laccase was characterized in a common wood-rotting fungus Fomes fomentarius, a species able to efficiently decompose dead wood, and compared to the production in eight other fungal species. The main aim of this study was to characterize the 1,4-β-glucosidase produced by F. fomentarius that was produced in high quantities in liquid stationary culture (25.9 U ml(-1)), at least threefold compared to other saprotrophic basidiomycetes, such as Rhodocollybia butyracea, Hypholoma fasciculare, Irpex lacteus, Fomitopsis pinicola, Pleurotus ostreatus, Piptoporus betulinus, and Gymnopus sp. (between 0.7 and 7.9 U ml(-1)). The 1,4-β-glucosidase enzyme was purified to electrophoretic homogeneity by both anion-exchange and size-exclusion chromatography. A single 1,4-β-glucosidase was found to have an apparent molecular mass of 58 kDa and a pI of 6.7. The enzyme exhibited high thermotolerance with an optimum temperature of 60 °C. Maximal activity was found in the pH range of 4.5-5.0, and K (M) and V (max) values were 62 μM and 15.8 μmol min(-1) l(-1), respectively, when p-nitrophenylglucoside was used as a substrate. The enzyme was competitively inhibited by glucose with a K (i) of 3.37 mM. The enzyme also acted on p-nitrophenylxyloside, p-nitrophenylcellobioside, p-nitrophenylgalactoside, and p-nitrophenylmannoside with optimal pH values of 6.0, 3.5, 5.0, and 4.0-6.0, respectively. The combination of relatively low molecular mass and low K (M) value make the 1,4-β-glucosidase a promising enzyme for biotechnological applications.

Influence of ligninolytic enzymes on straw saccharification during fungal pretreatment

Solid state and submerged fermentations in the presence of white-rot basidiomycetes (Bjerkandera adusta, Fomes fomentarius, Ganoderma resinaceum, Irpex lacteus, Phanerochaete chrysosporium, Trametes versicolor and basidiomycete Euc-1) and the litter-decomposing basidiomycete Lepista nuda were evaluated as a pretreatment to increase enzymatic saccharification of wheat straw. Enzymatic hydrolysis of holocellulose after solid state pretreatment showed a significant (P<0.05) increase of saccharification process for T. versicolor, Euc-1, G. resinaceum and I. lacteus, being T. versicolor (strain Tv2) the best one with a sugar yield increase of 91% compared with untreated straw. In submerged medium the pretreatment with I. lacteus, Euc-1 and P. chrysosporium enhanced saccharification but at a lesser extent. Covariance analysis was used to evaluate the relationships between ligninolytic enzymes (lignin peroxidase, manganese-dependent peroxidase and laccase) and saccharification increase. Results showed that only the presence of lignin peroxidase during pretreatment can lead to a significant (P<0.05) increase in the saccharification yield.

Immobilized laccase on a new cryogel carrier and kinetics of two anthraquinone derivatives oxidation

A coordinatively immobilized laccase was prepared using a new cryogel type carrier. The support has a wide-pore texture facilitating diffusion of different substrates to the enzyme reaction center. The biocatalyst proved to be efficient in decolorization of two anthraquinone derivatives, namely Acid Blue 62 and bromaminic acid. After 24 h over 80% of the two substrates have been oxidated. The kinetic data (K (m) and V (max)) for the oxidation of the two anthraquinone derivatives, with the free and immobilized enzyme, have been determined and compared. Other parameters, like k (cat) and the specificity constant have been calculated and analyzed. The influence of substrate properties (hydrophobicity, polarity, etc.) has been discussed.

Hyphal morphology modification in thermal adaptation by the white-rot fungus Fomes sp. EUM1

A thermotolerant white-rot fungus was identified as Fomes sp. EUM1. The strain exhibited maximum growth at 30 °C, with activation and inactivation energy values of 68 and 32 kJ/mol, respectively. The temperature affected the hyphal morphology, which was related to the thermotolerance of the microorganism: A shift from 30 to 40 °C in the growth temperature caused a decrease (15%) in mycelium branching; also longer (32%) and thinner (13%) hyphae were produced. In addition, as the temperature rose from 25 to 45 °C, an increase was observed in both the hyphal surface area (43%) and the surface growth rate (193%). The modification of the hyphal morphology suggests a strategy to colonize nutrient-rich areas while spending minimal energy for biomass formation under thermal stress.

Decolorization of Solophenyl Red 3BL Polyazo Dye by Laccase-Mediator System: Optimization through Response Surface Methodology

The decolorization of direct Solophenyl red 3BL (SR), a polyazo dye extensively used in textile industry was studied. The Fomes fomentarius laccase alone did not decolorize SR. The natural redox mediator, acetosyringone (AS), was necessary for decolorization to occur. Box-Behnken design was used to evaluate the effects of three parameters, namely, enzyme concentration (0.5-2.5 U mL(-1)), redox mediator concentration (3-30 μM), and incubation time (1-24 h), on the SR decolorization yield. The fitted mathematical model allowed us to plot response surfaces as well as isoresponse curves and to determine optimal decolorization conditions. The results clearly indicated that the AS concentration was the main factor influencing the SR decolorization yield. The selected optimal conditions were enzyme concentration 0.8 U mL(-1), mediator concentration 33 μM, and time 14 h 30 min. These conditions allowed 79.66% of SR decolorization versus 80.70% for the predicted value. These results showed a promising future of applying laccase-AS system for industrial wastewater bioremediation.

Purification and biochemical characterization of extracellular laccase from the ascomycete Paraconiothyrium variabile

An extracellular laccase-producing ascomycete was isolated from soil and identified as Paraconiothyrium variabile using rDNA sequence analysis. Typical laccase substrates including 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS), 2,6-dimethoxyphenol (DMP), and guaiacol were oxidized by the purified enzyme (designated as PvL). The molecular mass of PvL was 84 kDa and it showed a pI value of 4.2. The enzyme acted optimally at pH 4.8 and exhibited an optimum temperature of 50 °C. Using ABTS, PvL represented Km and Vmax of 203 μM and 40 μmol min(-1) mg(-1), respectively. After 24 h incubation at pH 4.8 and 4 °C, 80% of the initial activity of PvL remained. The enzyme was inhibited by Fe2+, Hg2+, and Mn2+, but induced by Cu2+. EDTA (10 mM), 1,4-dithiothreitol (DTT) (0.1 mM), and NaN3 (10 mM) were found to completely inhibit PvL. Sixty-eight percent of Malachite green was decolorized by 4 U/mL of PvL after 15 min incubation at 30 °C.