Characterization of optimized production, purification and application of laccase from Ganoderma lucidum

Valorization of bioethanol by-products to produce unspecific peroxygenase with Agrocybe aegerita: technological and proteomic perspectives

Unspecific peroxygenase (UPO) presents a wide range of biotechnological applications. This study targets the use of by-products from bioethanol synthesis to produce UPO by Agrocybe aegerita. Solid-state and submerged fermentations (SSF and SmF) were evaluated, achieving the highest titers of UPO and laccase in SmF using vinasse as nutrients source. Optimized UPO production of 331U/L was achieved in 50% (v:v) vinasse with an inoculum grown for 14 days. These conditions were scaled-up to a 4L reactor, achieving a UPO activity of 265U/L. Fungal proteome expression was analyzed before and after UPO activity appeared by shotgun mass spectrometry proteomics. Laccase, dye-decolorizing peroxidases (DyP), lectins and proteins involved in reactive oxygen species (ROS) production and control were detected (in addition to UPO). Interestingly, the metabolism of complex sugars and nitrogen sources had a different activity at the beginning and end of the submerged fermentation. DATA AVAILABILITY: The data used to support the findings of this study are available from the corresponding author upon reasonable request.

Nutraceutical Enrichment of Animal Feed by Filamentous Fungi Fermentation

There is an urgent need for improvements in animal production, particularly for ruminants, such that more sustainable and efficient processes are developed for obtaining more nutritious and efficient feeds. Filamentous fungi can add value to residual plant biomass, and may also have the potential to produce metabolites and enrich plant biomasses used in animal nutrition, converting them into nutraceutical sources. Thus, in this work, filamentous fungal fermentation of ruminant feed biomasses commonly used in Brazil was performed, and the enrichment for bioactive metabolites was tested. For this, Fistulina hepatica, Ganoderma lucidum, Pleurotus pulmonarius, Panus lecomtei, and Aspergillus terreus were grown for 28 days on different substrates: starchy grains- (sorghum, oat, and corn), fibrous substrates (coast-cross, rice husk, and moringa plant) and protein-rich substrates (cottonseed cake and pigeon pea plant). Fermented substrates were evaluated for laccase activity, crude protein, β-glucan, and lovastatin content. The highest growth rate was observed for G. lucidum in oat substrate (OT-01) (0.708 ± 0.035 cm/day) and F. hepatica in oat + coast-cross + pigeon pea treatment (OT-10) (0.607 ± 0.012 cm/day). High laccase activity was observed for P. lecomtei grown in starchy grain + moringa + pigeon pea substrate, reaching an activity of 416.8 ± 20.28 U/g. A. terreus growth in ST-09 (sorghum + pigeon pea) showed higher protein (15.3 ± 0.46%), β-glucan (503.56 ± 8.6 mg/g) and lovastatin (1.10 ± 0.17 mg/g) content compared to untreated substrates. These results demonstrate that filamentous fungi are an alternative for nutraceutical enrichment of ruminant feed biomasses. To the best of our knowledge, this is the first report in which P. lecomtei and F. hepatica are evaluated for their ability to be cultivated in ruminant feed substrates from Brazil.

Gllac7 Is Induced by Agricultural and Forestry Residues and Exhibits Allelic Expression Bias in Ganoderma lucidum

Ganoderma lucidum has a wide carbon spectrum, while the expression profile of key genes relevant to carbon metabolism on different carbon sources has been seldom studied. Here, the transcriptomes of G. lucidum mycelia cultured on each of 19 carbon sources were conducted. In comparison with glucose, 16 to 1,006 genes were upregulated and 7 to 1,865 genes were downregulated. Significant gene expression dynamics and induced activity were observed in laccase genes when using agricultural and forestry residues (AFRs) as solo carbon sources. Furthermore, study of laccase gene family in two haploids of G. lucidum GL0102 was conducted. Totally, 15 and 16 laccase genes were identified in GL0102_53 and GL0102_8, respectively, among which 15 pairs were allelic genes. Gene structures were conserved between allelic laccase genes, while sequence variations (most were SNPs) existed. Nine laccase genes rarely expressed on all the tested carbon sources, while the other seven genes showed high expression level on AFRs, especially Gllac2 and Gllac7, which showed 5- to 1,149-fold and 4- to 94-fold upregulation in mycelia cultured for 5 days, respectively. The expression of H53lac7 was consistently higher than that of H8lac7_1 on all the carbon sources except XM, exhibiting a case of allelic expression bias. A total of 47 SNPs and 3 insertions/deletions were observed between promoters of H53lac7 and H8lac7_1, which lead to differences in predicted binding sites of zinc fingers. These results provide scientific data for understanding the gene expression profile and regulatory role on different carbon sources and may support further functional research of laccase.

Biodegradation of cyclophosphamide and etoposide by white rot fungi and their degradation kinetics

The biodegradation of cyclophosphamide and etoposide by Trametes versicolor (AH05), Ganoderma lucidum (MTCC-1039), and Phanerochaete chrysosporium (MTCC-787) were tested for 3, 6, 9, 12, and 15 days, respectively. G. lucidum achieved the highest degradation efficiency of cyclophosphamide (71.5%) and etoposide (98.4%) after 6 days of treatment. The degradation efficiency of T. versicolor and P. chrysosporium for etoposide was 79.8% and 76.8%, respectively. However, no degradation of cyclophosphamide was achieved with P. chrysosporium, although it showed the highest sorption efficiency for cyclophosphamide (23.7%). Trametes versicolor achieved only 1.4% degradation of cyclophosphamide, that includes both biodegradation and biosorption. The pseudo first-order degradation kinetics explained the degradation of etoposide and cyclophosphamide with t_1/2 values of 1.32 and 4.43 days and 'k' constant of 0.16 and 0.54 day^-1, respectively.

Recent Developments in the Immobilization of Laccase on Carbonaceous Supports for Environmental Applications - A Critical Review

Τhe ligninolytic enzyme laccase has proved its potential for environmental applications. However, there is no documented industrial application of free laccase due to low stability, poor reusability, and high costs. Immobilization has been considered as a powerful technique to enhance laccase's industrial potential. In this technology, appropriate support selection for laccase immobilization is a crucial step since the support could broadly affect the properties of the resulting catalyst system. Through the last decades, a large variety of inorganic, organic, and composite materials have been used in laccase immobilization. Among them, carbon-based materials have been explored as a support candidate for immobilization, due to their properties such as high porosity, high surface area, the existence of functional groups, and their highly aromatic structure. Carbon-based materials have also been used in culture media as supports, sources of nutrients, and inducers, for laccase production. This study aims to review the recent trends in laccase production, immobilization techniques, and essential support properties for enzyme immobilization. More specifically, this review analyzes and presents the significant benefits of carbon-based materials for their key role in laccase production and immobilization.

Selection of a pH- and temperature-stable laccase from Ganoderma australe and its application for bioremediation of textile dyes

By virtue of screening, purification, and properties characterization, this study captures a new pH- and temperature-stable laccase, designated Galacc-F, from Ganoderma australe for dye bioremediating applications. The enzyme was purified to homogeneity by salt precipitation, ionic exchange, and size exclusion chromatography with a final specific activity of 22.214 U mg^-1, yielding a purification fold of 23.989 and recovery of 38.44%. Its molecular weight was estimated to be 48.0 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, zymography, Sephadex G-100 column, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, which confirmed its monomeric nature. Galacc-F exhibited high levels of activity and stability over wide ranges of pH (5.0-8.0) and temperature (10-60 °C), which are highly valuable properties in industrial processes. Broad substrate specificity was observed, wherein a better affinity was found for 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) with a low value of K_m (164.137 μM) and higher k_cat/K_m ratio (1.663 s^-1 μM^-1). Activity was stimulated by Cu²⁺ and β-mercaptoethanol but inhibited by ethylenediaminetetraacetic acid, diethylpyrocarbonate, iodoacetic acid, phenylmethylsulfonyl fluoride, and Hg²⁺, indicating that Galacc-F is a metalloprotease containing a typical histidine-cysteine-serine catalytic triad. It had high tolerance to surfactants, oxidants, and salts. Additionally, a fabricated protocol for native Galacc-F immobilization onto Fe₃O₄@Chitosan composite nanoparticles using glutaraldehyde as a crosslinker was developed. Most importantly, the enzyme was determined to be ideal for use in efficient treatment of dye effluents as compared with the laccases requiring redox mediators.

Introducing a Thermo-Alkali-Stable, Metallic Ion-Tolerant Laccase Purified From White Rot Fungus Trametes hirsuta

This study introduces a valuable laccase, designated ThLacc-S, purified from white rot fungus Trametes hirsuta. ThLacc-S is a monomeric protein in nature with a molecular weight of 57.0 kDa and can efficiently metabolize endocrine disrupting chemicals. The enzyme was successfully purified to homogeneity via three consecutive steps consisting of salt precipitation and column chromatography, resulting in a 20.76-fold increase in purity and 46.79% yield, with specific activity of 22.111 U/mg protein. ThLacc-S was deciphered as a novel member of the laccase family and is a rare metalloenzyme that contains cysteine, serine, histidine, and tyrosine residues in its catalytic site, and follows Michaelis-Menten kinetic behavior with a K _m and a k _cat /K _m of 87.466 μM and 1.479 s^-1μM^-1, respectively. ThLacc-S exerted excellent thermo-alkali stability, since it was markedly active after a 2-h incubation at temperatures ranging from 20 to 70°C and retained more than 50% of its activity after incubation for 72 h in a broad pH range of 5.0-10.0. Enzymatic activities of ThLacc-S were enhanced and preserved when exposed to metallic ions, surfactants, and organic solvents, rendering this novel enzyme of interest as a green catalyst for versatile biotechnological and industrial applications that require these singularities of laccases, particularly biodegradation and bioremediation of environmental pollutants.

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.

Substrate specificity of a new laccase from Trametes polyzona WRF03

Various aromatic compounds that are structurally analogous to lignin were tested as possible/preferred substrates for purified laccase from newly isolated white rote fungi, Trametes polyzona WRF03. The pH optima were tested using different substrates and kinetic studies were conducted at these pH optima. The pH optima in the presence of ABTS, α-naphthol, o-dianisidine, and catechol were 4.5 but 5.0 and 5.5 in the presence of guaiacol and pyrogallol, respectively. The initial velocities obtained from the kinetic study were analyzed using Graph Pad Prism 7 and Lineweaver-Burk plot to obtain kinetic constants (k_m and _Vmax) which were used to calculate substrate specificity. Amongst all the substrates tested, ABTS had the highest specificity-constant (181.51 M⁻¹s⁻¹), and therefore, the most preferred substrate was followed by α-naphthol, o-dianisidine, guaiacol, pyrogallol, and catechol. Resorcinol, orcinol, and veratryl alcohol did not display any considerable chemical shift in the presence of Trametes polyzona WRF03 laccase. Also, oxidation of phenolic substrates appeared to be dependent on the nature of the substituent groups and their relative position on the aromatic nucleus. Since most of these substrates are structural analogs of lignin and many recalcitrant environmental pollutants, the enzyme may find application in delignification, treatment of wastewater containing dyes, and polycyclic aromatic hydrocarbons (PAHs).

Purification and characterisation of new laccase from Trametes polyzona WRF03

•

Trametes polyzona WRF03 produced high yield of true laccase.

•

Trametes polyzona WRF03 laccase was relatively pH and temperature stable.

•

Fe²⁺, sodium azide and sodium cyanide greatly inhibited laccase activity.

•

Trametes polyzona WRF03 laccase decolorised many classes of synthetic dyes.

The molecular screening for laccase specific gene sequences in Trametes polyzona WRF03 (TpWRF03) using designed oligonucleotide primers analogous to the conserved sequences on the copper-binding regions of known laccases showed positive amplification with an amplicon size corresponding to 1500 bp. The purified TpWRF03 laccase (TpL) is a monomer with a molecular weight corresponding to 66 kDa. The enzyme had an optimal pH of 4.5 and temperature of 55 °C. TpL was most stable within pH of 5.5–6.5 and at a temperature range of 40–50 °C. Sodium azide, sodium cyanide and Fe²⁺ greatly inhibited the enzyme activity. TpL showed more than 50 % decolourisation efficiency on coomassie brilliant blue (72.35 %) and malachite green (57.84 %) but displayed low decolourisation efficiency towards Azure B (1.78 %) and methylene blue (0.38 %). The results showed that TpWRF03 produces high-yield of true laccase with robust properties for biotechnological applications.

Laccase production by Trametes versicolor in solid-state fermentation using tea residues as substrate and its application in dye decolorization

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.

Sequential degradation of raw vinasse by a laccase enzyme producing fungus Pleurotus sajor-caju and its ATPS purification

•

Vinasse degradation and laccase production by Pleurotus sajor-caju were performed;

•

Laccase activity induction by copper sulfate and ethanol in raw vinasse as substrate was confirmed;

•

Fermentation time to maximum laccase activity was reduced to just 3 days when cooper sulfate was used as inducer;

•

The use of laccase inducers does not interfere with decolorization and turbidity removal;

•

Aqueous two-phase systems reached 2.88-fold in laccase purification, with recovery of ∼ 99.9% to upper phase (PEG-rich phase).

This study evaluated simultaneously the raw vinasse degradation, an effluent from the sugar-alcohol industry, the laccase production by Pleurotus sajor-caju and its purification using aqueous two-phase systems (ATPS). To improve laccase production, different concentrations of inducers (ethanol and CuSO₄) were added. The higher laccase production promoted an increase of 4-fold using 0.4 mM of CuSO₄ as inducer, with maximum enzymatic activity of 539.3 U/L on the 3^rd day of fermentation. The final treated vinasse had a decolorization of 92% and turbidity removal of 99% using CuSO₄. Moreover, the produced laccase was then purified by ATPS in a single purification step, reaching 2.9-fold and recovered ≈ 99,9 %, in the top phase (PEG-rich phase) using 12 wt% of PEG 1500 + 20 wt% of citrate buffer + enzyme broth + water, at 25 °C. Thus, an integrated process of vinasse degradation, laccase production and purification with potential industrial application was proposed.

Copper induces transcription of BcLCC2 laccase gene in phytopathogenic fungus, Botrytis cinerea

Laccases are one of many groups of inducible enzymes produced by the filamentous fungus, Botrytis cinerea during colonisation of host plant tissues. While the processes involved in laccase induction are not fully understood, Cupric ions (e.g. CuSO₄) and gallic acid (GA) have been reported as laccase inducers. This study investigates laccases activities and the expression of three laccase genes (BcLCC1, BcLCC2, BcLCC3) in three B. cinerea isolates grown in laccase-inducing medium (LIM) supplemented with CuSO₄ and GA. Laccase activity in culture filtrates with CuSO₄ increased after 48 h of growth in LIM at 24°C. The induction of BcLCC2 transcription was greatest at a concentration of 0.6 mM CuSO₄, concentrations greater than 0.6 mM inhibited fungal growth. In contrast, no laccase induction was observed in the presence of GA. Liquid chromatography-mass spectroscopy (NanoLC ESI MS/MS) analysis confirmed the presence of a 63.4 kDa protein, the BcLCC2 isoform in the culture filtrate with 0.6 mM CuSO₄. Analysis of mRNA transcripts further showed BcLCC3 was also inducible and the expression of BcLCC2 and BcLCC3 was isolate-dependent. In conclusion, CuSO₄ induces a 63.4 kDa laccase in B. cinerea by induced transcription of the BcLCC2 gene.

Improvement of Saccharification and Delignification Efficiency of Trichoderma reesei Rut-C30 by Genetic Bioengineering

Trichoderma reesei produces various saccharification enzymes required for biomass degradation. However, the lack of an effective lignin-degrading enzyme system reduces the species’ efficiency in producing fermentable sugars and increases the pre-treatment costs for biofuel production. In this study, we heterologously expressed the Ganoderma lucidum RMK1 versatile peroxidase gene (vp1) in the Rut-C30 strain of T. reesei. The expression of purified 6×His-tag–containing recombinant G. lucidum-derived protein (rVP1) was confirmed through western blot, which exhibited a single band with a relative molecular weight of 39 kDa. In saccharification and delignification studies using rice straw, the transformant (tVP7, T. reesei Rut-C30 expressing G. lucidum-derived rVP1) showed significant improvement in the yield of total reducing sugar and delignification, compared with that of the parent T. reesei Rut-C30 strain. Scanning electron microscopy (SEM) of tVP7-treated paddy straw showed extensive degradation of several layers of its surface compared with the parent strain due to the presence of G. lucidum-derived rVP1. Our results suggest that the expression of ligninolytic enzymes in cellulase hyperproducing systems helps to integrate the pre-treatment and saccharification steps that may ultimately reduce the costs of bioethanol production.

Exploiting the potential of metal and solvent tolerant laccase from Tricholoma giganteum AGDR1 for the removal of pesticides

Laccase from previously reported hardwood degrading fungus, Tricholoma giganteum AGDR1, was isolated, identified at molecular level, biochemically characterized and also utilized for pesticide degradation. Laccase gene is comprised of 3752 bp, which encompassed 742-bp of 5' flanking upstream sequence with 12 introns and 12 exons. Mature enzyme possesses 391 amino acids and signal peptide, which is determined to be monomeric protein with an apparent molecular weight of 41 kDa and 6.45 pI. Higher optimal activities were observed at 45 °C and pH 3.0 and surprisingly, it exhibited more than 20% of relative activity at pH 1.5. Purified laccase was tolerant to 100 mM of metals (i.e. Se, Pb, Cu, Cr and Cd), organic solvents (ethyl acetate, methanol, ethanol and acetone) and potent inhibitors (hydroxylamine, thiourea, NaF and Na-azide) as compared to reported laccases. It was able to degrade 29%, 7% and 72% of chlorpyrifos, profenofos and thiophanate methyl within 15 h, respectively. Molecular docking analysis revealed that higher binding efficacy of these pesticides is observed with H83, H320, A95, V384, and P366 which are presented near to the catalytic site. Based on the results, T. giganteum AGDR1 laccase can be applied for the potential remediation and industrial applications under harsh conditions.

Media improvement for 10 L bioreactor production of rPOXA 1B laccase by P. pastoris

In this work, we statistically improved culture media for rPOXA 1B laccase production, expressed in Pichia pastoris containing pGAPZαA-LaccPost-Stop construct and assayed at 10 L bioreactor production scale (6 L effective work volume). The concentrated enzyme was evaluated for temperature and pH stability and kinetic parameter, characterized by monitoring oxidation of different ABTS [2, 20-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)] substrate concentrations. Plackett-Burman experimental design (PBED) implementation improved previous work results by 3.05-fold, obtaining a laccase activity of 1373.72 ± 0.37 U L^-1 at 168 h of culture in a 500 mL shake flask. In contrast, one factor experimental design (OFED) applied after PBED improved by threefold the previous study, additionally increasing the C/N ratio. Employing OFED media at 10 L bioreactor scale was capable of producing 3159.93 ± 498.90 U L^-1 at 192 h, representing a 2.4-fold increase. rPOXA 1B concentrate remained stable between 10 and 50 °C and retained over 70% residual enzymatic activity at 60 °C and 50% at 70 °C. Concerning pH stability, the enzyme was stable at pH 4.0 ± 0.2 with a residual activity greater than 90%. The lowest residual activity (60%) was obtained at pH 10.0 ± 0.2. Furthermore, the apparent kinetic parameters were V _max of 3.163 × 10^-2 mM min^-1 and K _m of 1.716 mM. Collectively, regarding enzyme stability our data provide possibilities for applications involving a wide range of pH and temperatures.

Optimization of Laccase from Ganoderma lucidum Decolorizing Remazol Brilliant Blue R and Glac1 as Main Laccase-Contributing Gene

Many dyes and pigments are used in textile and printing industries, and their wastewater has been classed as a top source of pollution. Biodegradation of dyes by fungal laccase has great potential. In this work, the influence of reaction time, pH, temperature, dye concentration, metal ions, and mediators on laccase-catalyzed Remazol Brilliant Blue R dye (RBBR) decolorization were investigated in vitro using crude laccase from the white-rot fungus Ganoderma lucidum. The optimal decolorization percentage (50.3%) was achieved at 35 °C, pH 4.0, and 200 ppm RBBR in 30 min. The mediator effects from syringaldehyde, 1-hydroxybenzotriazole, and vanillin were compared, and 0.1 mM vanillin was found to obviously increase the decolorization percentage of RBBR to 98.7%. Laccase-mediated decolorization percentages significantly increased in the presence of 5 mM Na+ and Cu2+, and decolorization percentages reached 62.4% and 62.2%, respectively. Real-time fluorescence-quantitative PCR (RT-PCR) and protein mass spectrometry results showed that among the 15 laccase isoenzyme genes, Glac1 was the main laccase-contributing gene, contributing the most to the laccase enzyme activity and decolorization process. These results also indicate that under optimal conditions, G. lucidum laccases, especially Glac1, have a strong potential to remove RBBR from reactive dye effluent.

Evaluation of laccase production by Ganoderma lucidum in submerged and solid-state fermentation using different inducers

Laccases are multicopper oxidases with high potential for industrial applications. Several basidiomycete fungi are natural producers of this enzyme; however, the optimization of production and selection of inducers for increased productivity coupled with low costs is necessary. Lignocellulosic residues are important lignin sources and potential inducers for laccase production. Pinus taeda, a dominant source of wood-based products, has not been investigated for this purpose yet. The aim of this study was to evaluate the production of laccase by the basidiomycete fungus Ganoderma lucidum in the presence of different inducers in submerged and solid-state fermentation. The results of submerged fermentation in presence of 5 μM CuSO ₄ , 2 mM ferulic acid, 0.1 g/L P. taeda sawdust, or 0.05 g/L Kraft lignin indicated that although all the tested inducers promoted increase in laccase activity in specific periods of time, the presence of 2 mM ferulic acid resulted in the highest value of laccase activity (49 U/L). Considering the submerged fermentation, experimental design following the Plackett-Burman method showed that the concentrations of ferulic acid and P. taeda sawdust had a significant influence on the laccase activity. The highest value of 785 U/L of laccase activity on submerged fermentation was obtained on the seventh day of cultivation. Finally, solid-state fermentation cultures in P. taeda using ferulic acid or CuSO ₄ as inducers resulted in enzymatic activities of 144.62 and 149.89 U/g, respectively, confirming the potential of this approach for laccase production by G. lucidum.

Biodegradation of polycyclic aromatic hydrocarbons by native Ganoderma sp. strains: identification of metabolites and proposed degradation pathways

Since polycyclic aromatic hydrocarbons (PAHs) are mutagenic, teratogenic, and carcinogenic, they are of considerable environmental concern. A biotechnological approach to remove such compounds from polluted ecosystems could be based on the use of white-rot fungi (WRF). The potential of well-adapted indigenous Ganoderma strains to degrade PAHs remains underexplored. Seven native Ganoderma sp. strains with capacity to produce high levels of laccase enzymes and to degrade synthetic dyes were investigated for their degradation potential of PAHs. The crude enzymatic extracts produced by Ganoderma strains differentially degraded the PAHs assayed (naphthalene 34-73%, phenanthrene 9-67%, fluorene 11-64%). Ganoderma sp. UH-M was the most promising strain for the degradation of PAHs without the addition of redox mediators. The PAH oxidation performed by the extracellular enzymes produced more polar and soluble metabolites such as benzoic acid, catechol, phthalic and protocatechuic acids, allowing us to propose degradation pathways of these PAHs. This is the first study in which breakdown intermediates and degradation pathways of PAHs by a native strain of Ganoderma genus were determined. The treatment of PAHs with the biomass of this fungal strain enhanced the degradation of the three PAHs. The laccase enzymes played an important role in the degradation of these compounds; however, the role of peroxidases cannot be excluded. Ganoderma sp. UH-M is a promising candidate for the bioremediation of ecosystems polluted with PAHs.

From agro-waste to tool: biotechnological characterization and application of Ganoderma lucidum E47 laccase in dye decolorization

The culture of fungal species from agro-waste allows for the sustainable preparation of valuable biotechnological products and contributes to establish the Circular Economy concept. The Ganoderma lucidum species is well known as producer of laccases (EC 1.10.3.2), which serves as a tool to oxidize chemicals. When producing G. lucidum E47 basidiomes with edible purposes out of rice crop residues, its laccase remains as by-product. In this work, we report the biotechnological characterization and application of the laccase recovered from spent cultures of the G. lucidum E47 strain. We detected at least one polypeptide (ca. 59 kDa) which displays attractive activity and stability values when used in the range of 18-45 °C in mildly acidic environment (pH 4.8-5.8). These parameters can be enhanced in the presence of organic cosolvents such as butyl acetate and methyl iso-butyl ketone, but the opposite effect is observed with solvents of lower log P. The best activity-stability performance is reached when the biocatalyst is used in pH 4.8 buffer with 5% (v/v) butyl acetate at 37 °C. The laccase was capable of decolorizing xanthene, azo and triarylmethane dyes, exhibiting excellent selectivity on bromocresol green and bromocresol purple. Furthermore, the biocatalyst displayed an attractive activity when assessed for the decolorization of bromocresol green in a proof-of-concept effluent biotreatment.

Fungal biodegradation of the N-nitrosodimethylamine precursors venlafaxine and O-desmethylvenlafaxine in water

Antidepressant drugs such as Venlafaxine (VFX) and O-desmethylvenlafaxine (ODMVFX) are emerging contaminants that are commonly detected in aquatic environments, since conventional wastewater treatment plants are unable to completely remove them. They can be precursors of hazardous by-products, such as the carcinogenic N-nitrosodimethylamine (NDMA), generated upon water chlorination, as they contain the dimethylamino moiety, necessary for the formation of NDMA. In this study, the capability of three white rot fungi (Trametes versicolor, Ganoderma lucidum and Pleurotus ostreatus) to remove both antidepressants from water and to decrease NDMA formation potential was investigated. Furthermore, transformation by-products (TPs) generated along the treatment process were elucidated and also correlated with their NDMA formation potential. Very promising results were obtained for T. versicolor and G. lucidum, both being able to remove up to 100% of ODMVFX. In the case of VFX, which is very recalcitrant to conventional wastewater treatment, a 70% of removal was achieved by T. versicolor, along with a reduction in NDMA formation potential, thus decreasing the associated problems for human health and the environment. However, the NDMA formation potential remained practically constant during treatment with G. lucidum despite of the equally high VFX removal (70%). This difference was attributed to the generation of different TPs during both fungal treatments. For example, G. lucidum generated more ODMVFX, which actually has a higher NDMA formation potential than the parent compound itself.

Diversity of Ligninolytic Enzymes and Their Genes in Strains of the Genus Ganoderma: Applicable for Biodegradation of Xenobiotic Compounds?

White-rot fungi (WRF) and their ligninolytic enzymes (laccases and peroxidases) are considered promising biotechnological tools to remove lignin related Persistent Organic Pollutants from industrial wastewaters and contaminated ecosystems. A high diversity of the genus Ganoderma has been reported in Cuba; in spite of this, the diversity of ligninolytic enzymes and their genes remained unexplored. In this study, 13 native WRF strains were isolated from decayed wood in urban ecosystems in Havana (Cuba). All strains were identified as Ganoderma sp. using a multiplex polymerase chain reaction (PCR)-method based on ITS sequences. All Ganoderma sp. strains produced laccase enzymes at higher levels than non-specific peroxidases. Native-PAGE of extracellular enzymatic extracts revealed a high diversity of laccase isozymes patterns between the strains, suggesting the presence of different amino acid sequences in the laccase enzymes produced by these Ganoderma strains. We determined the diversity of genes encoding laccases and peroxidases using a PCR and cloning approach with basidiomycete-specific primers. Between two and five laccase genes were detected in each strain. In contrast, only one gene encoding manganese peroxidase or versatile peroxidase was detected in each strain. The translated laccases and peroxidases amino acid sequences have not been described before. Extracellular crude enzymatic extracts produced by the Ganoderma UH strains, were able to degrade model chromophoric compounds such as anthraquinone and azo dyes. These findings hold promises for the development of a practical application for the treatment of textile industry wastewaters and also for bioremediation of polluted ecosystems by well-adapted native WRF strains.

Biotransformation of lignocellulosic materials into value-added products-A review

In the past decade, with the key biotechnological advancements, lignocellulosic materials have gained a particular importance. In serious consideration of global economic, environmental and energy issues, research scientists have been re-directing their interests in (re)-valorizing naturally occurring lignocellulosic-based materials. In this context, lignin-modifying enzymes (LMEs) have gained considerable attention in numerous industrial and biotechnological processes. However, their lower catalytic efficiencies and operational stabilities limit their practical and multipurpose applications in various sectors. Therefore, to expand the range of natural industrial biocatalysts e.g. LMEs, significant progress related to the enzyme biotechnology has appeared. Owing to the abundant lignocellulose availability along with LMEs in combination with the scientific advances in the biotechnological era, solid-phase biocatalysts can be economically tailored on a large scale. This review article outlines first briefly on the lignocellulose materials as a potential source for biotransformation into value-added products including composites, fine chemicals, nutraceutical, delignification, and enzymes. Comprehensive information is also given on the purification and characterization of LMEs to present their potential for the industrial and biotechnological sector.

Pilot-scale bioconversion of rice and sunflower agro-residues into medicinal mushrooms and laccase enzymes through solid-state fermentation with Ganoderma lucidum

Solid-state fermentation was evaluated at the pilot-scale for the bioconversion and valorization of rice husks and straw (RSH), or sunflower seed hulls (SSH), into medicinal mushrooms and crude extracts, with laccase activity. The average mushroom yield was 56kg dry weight per ton of agro-residues. Laccase activity in crude aqueous extracts showed its maximum value of 10,927Ukg^-1 in RSH (day 10, Exudate phase) and 16,442Ukg^-1 in SSH (day 5, Full colonization phase), the activity at the Residual substrate phase being 511Ukg^-1 in RSH and 803Ukg^-1 in SSH, respectively. Crude extracts obtained with various protocols revealed differences in the extraction yields. Lyophilization followed by storage at 4°C allowed the preservation of laccase activity for more than one month. It is proposed that standard mushroom farms could increase their profits by obtaining laccase as a byproduct during the gaps in mycelium running.

Plackett-Burman Design for rGILCC1 Laccase Activity Enhancement in Pichia pastoris: Concentrated Enzyme Kinetic Characterization

Laccases are multicopper oxidases that catalyze aromatic and nonaromatic compounds with concomitant reduction of molecular oxygen to water. They are of great interest due to their potential biotechnological applications. In this work we statistically improved culture media for recombinant GILCC1 (rGILCC1) laccase production at low scale from Ganoderma lucidum containing the construct pGAPZαA-GlucPost-Stop in Pichia pastoris. Temperature, pH stability, and kinetic parameter characterizations were determined by monitoring concentrate enzyme oxidation at different ABTS substrate concentrations. Plackett-Burman Design allowed improving enzyme activity from previous work 36.08-fold, with a laccase activity of 4.69 ± 0.39 UL⁻¹ at 168 h of culture in a 500 mL shake-flask. Concentrated rGILCC1 remained stable between 10 and 50°C and retained a residual enzymatic activity greater than 70% at 60°C and 50% at 70°C. In regard to pH stability, concentrated enzyme was more stable at pH 4.0 ± 0.2 with a residual activity greater than 90%. The lowest residual activity greater than 55% was obtained at pH 10.0 ± 0.2. Furthermore, calculated apparent enzyme kinetic parameters were a V_max of 6.87 × 10⁻⁵ mM s⁻¹, with an apparent K_m of 5.36 × 10⁻² mM. Collectively, these important stability findings open possibilities for applications involving a wide pH and temperature ranges.

Physiological Regulation of an Alkaline-Resistant Laccase Produced by Perenniporia tephropora and Efficiency in Biotreatment of Pulp Mill Effluent

Regulation of alkaline-resistant laccase from Perenniporia tephropora KU-Alk4 was proved to be controlled by several factors. One important factor was the initial pH, which drove the fungus to produce different kinds of ligninolytic enzymes. P. tephropora KU-Alk4 could grow at pH 4.5, 7.0, and 8.0. The fungus produced laccase and MnP at pH 7.0, but only laccase at pH 8.0. The specific activity of laccase in the pH 8.0 culture was higher than that in the pH 7.0 culture. At pH 8.0, glucose was the best carbon source for laccase production but growth was better with lactose. Low concentrations of glucose at 0.1% to 1.0% enhanced laccase production, while concentrations over 1% gave contradictory results. Veratryl alcohol induced the production of laccase. A trace concentration of copper ions was required for laccase production. Biomass increased with an increasing rate of aeration of shaking flasks from 100 to 140 rpm; however, shaking at over 120 rpm decreased laccase quantity. Highest amount of laccase produced by KU-Alk4, 360 U/mL, was at pH 8.0 with 1% glucose and 0.2 mM copper sulfate, unshaken for the first 3 days, followed by addition of 0.85 mM veratryl alcohol and shaking at 120 rpm. The crude enzyme was significantly stable in alkaline pH 8.0~10.0 for 24 hr. After treating the pulp mill effluent with the KU-Alk4 system for 3 days, pH decreased from 9.6 to 6.8, with reduction of color and chemical oxygen demand at 83.2% and 81%, respectively. Laccase was detectable during the biotreatment process.

Biodegradation of polycyclic aromatic hydrocarbons by a thermotolerant white rot fungus Trametes polyzona RYNF13

The biodegradation of three polycyclic aromatic hydrocarbons (PAHs), phenanthrene, fluorene, and pyrene, by a newly isolated thermotolerant white rot fungal strain RYNF13 from Thailand, was investigated. The strain RYNF13 was identified as Trametes polyzona, based on an analysis of its internal transcribed spacer sequence. The strain RYNF13 was superior to most white rot fungi. The fungus showed excellent removal of PAHs at a high concentration of 100 mg·L^-1. Complete degradation of phenanthrene in a mineral salt glucose medium culture was observed within 18 days of incubation at 30°C, whereas 90% of fluorene and 52% of pyrene were degraded under the same conditions. At a high temperature of 42°C, the strain RYNF13 was still able to grow, and degraded approximately 68% of phenanthrene, whereas 48% of fluorene and 30% of pyrene were degraded within 32 days. Thus, the strain RYNF13 is a potential fungus for PAH bioremediation, especially in a tropical environment where the temperature can be higher than 40°C. The strain RYNF13 secreted three different ligninolytic enzymes, manganese peroxidase, laccase, and lignin peroxidase, during PAH biodegradation at 30°C. When the incubation temperature was increased from 30°C to 37°C and 42°C, only two ligninolytic enzymes, manganese peroxidase and laccase, were detectable during the biodegradation. Manganese peroxidase was the major enzyme produced by the fungus. In the culture containing phenanthrene, manganese peroxidase showed the highest enzymatic activity at 179 U·mL^-1. T. polyzona RYNF13 was determined as a potential thermotolerant white rot fungus, and suitable for application in the treatment of PAH-containing contaminants.

Isolation and Physicochemical Characterization of Laccase from Ganoderma lucidum-CDBT1 Isolated from Its Native Habitat in Nepal

At present, few organisms are known to and capable of naturally producing laccases and white rot fungi are one such group. In the present study, three fungal species, namely, Ganoderma lucidum-CDBT1, Ganoderma japonicum, and Lentinula edodes, isolated from their native habitat in Nepal were screened for laccase production, and G. lucidum-CDBT1 was found to express highest levels of enzyme (day 10 culture media showed 0.92 IU/mg total protein or 92 IU/mL laccase activity with ABTS as substrate). Lignin extracted from rice straw was used in Olga medium for laccase production and isolation from G. lucidum-CDBT1. Presence of lignin (5 g/L) and copper sulfate (30 μM) in the media increased the extracellular laccase content by 111% and 114%, respectively. The laccase enzyme produced by G. lucidum-CDBT1 was fractionated by ammonium sulfate and purified by DEAE Sepharose anion exchange chromatography. The purified enzyme was found to have a molecular mass of 43 kDa and exhibits optimal activity at pH 5.0 and 30°C. The isolated laccase was thermally stable for up to 70°C for 1 h and exhibited broad pH stability. The kinetic constants, K_m, V_max, and K_cat, determined using 2,2′-azinobis-(-3-ethylbenzothiazoline-6-sulfonic acid) as substrate were found to be 110 μM, 36 μmol/min/mg, and 246 min⁻¹, respectively. The isolated thermostable laccase will be used in future experiments for delignification process.

Biodegradation of phenolic compounds by Basidiomycota and its phenol oxidases: A review

The phylum Basidiomycota include organisms with enormous bioremediation potential. A variety of processes were proposed at the lab scale for using these fungi and their phenol oxidases in the degradation of phenolics. Here we present a survey of this topic using literature published mostly over the last 10 years. First, the sources of the enzymes are summarized. The laccase and tyrosinase were mainly from Trametes versicolor and Agaricus bisporus, respectively. Recently, however, new promising wild-type producers of the enzymes have emerged and a number of recombinant strains were also constructed, based mainly on yeasts or Aspergillus strains as hosts. The next part of the study summarizes the enzyme and whole-cell applications for the degradation of phenols, polyphenols, cresols, alkylphenols, naphthols, bisphenols and halogenated (bis)phenols in model mixtures or real wastewaters from the food, paper and coal industries, or municipal and hospital sewage. The enzymes were applied as free (crude or purified) enzymes or as enzymes immobilized in various supports or CLEAs, and optionally recycled or used in continuous mode. Alternatively, growing cultures or harvested mycelia were used instead. The products, which were characterized as quinones and their polymers in some cases, could be eliminated by filtration, flocculation or adsorption onto chitosan. The purity of a treated wastewater was monitored using a sensitive aquatic organism. It is concluded that low-cost sources of these enzymes should be searched for and the benefits of enzymatic, biological and physico-chemical methods could be combined to make the processes fit for industrial use.

Prickly palm cactus husk as a raw material for production of ligninolytic enzymes by Aspergillus niger

Prickly palm cactus husk was used as a solid-state fermentation support-substrate for production of the ligninolytic enzymes laccase, peroxide manganese, and lignin peroxidase by Aspergillus niger. Effects of water activity, temperature, and fermentation time on enzymatic production were evaluated using a central composite rotatable design. Response surface methodology revealed that maximum enzyme production was achieved at 73.38 h of fermentation, a water activity of 0.87 Aw, at 28.74°C for laccase, at 65.33 h, 0.89 Aw, and 28.96°C for lignin peroxidase, and at 70.44 h, 0.91 Aw, and 28.84°C for manganese peroxidase. Optimized enzyme production was 9,023.67 UI/L for laccase, 2,234.75 UI/L for lignin peroxidase, and 8,534.81 UI/L for manganese peroxidase. Thermostability and pH stability were observed for all enzymes. Enzymatic deactivation kinetic experiments indicated that enzymes remained active after freezing of crude extracts.

Characterization of a novel endoglucanase from Ganoderma lucidum

We evaluated the production and characterization of endoglucanase from Ganoderma lucidum using different lignocellulose biomasses. We purified a novel carboxymethyl cellulose (CMC) hydrolyzing endoglucanase from the white-rot fungus G. lucidum when the medium was supplemented with 1% (w/v) wheat bran. Endoglucanase was purified 12.5-fold via ammonium sulfate fractionation, Sephadex G-100, and Q-Sepharose column chromatography with a final yield of 15%. SDS-PAGE analysis revealed that the endoglucanase had a molecular mass of 64.0 kDa. The optimal activity of purified endoglucanase was at pH 5.0 and 35 °C, though it was stable between pH 4.0-7.0 and temperatures of 30-60 °C. The purified enzyme was specific to CMC as a suitable substrate. The metal ions Hg(2+), Fe(2+), and Cr(2+) inhibited enzyme activity, while Ca(2+), Mg(2+), and Mn(2+) enhanced enzyme activity. The endoglucanase showed high activity and stability in the presence of different surfactants and non-polar hydrophobic organic solvents. This endoglucanase is tolerant to high temperature, metal ions, surfactants, and solvents, suggesting that it is appropriate for use in biomass conversion for biofuel production under harsh environmental conditions.

Identification of a laccase Glac15 from Ganoderma lucidum 77002 and its application in bioethanol production

BACKGROUND

Laccases have potential applications in detoxification of lignocellulosic biomass after thermochemical pretreatment and production of value-added products or biofuels from renewable biomass. However, their application in large-scale industrial and environmental processes has been severely thwarted by the high cost of commercial laccases. Therefore, it is necessary to identify new laccases with lower cost but higher activity to detoxify lignocellulosic hydrolysates and better efficiency to produce biofuels such as bioethanol. Laccases from Ganoderma lucidum represent proper candidates in processing of lignocellulosic biomass.

RESULTS

G. lucidum 77002 produces three laccase isoenzymes with a total laccase activity of 141.1 U/mL within 6 days when using wheat bran and peanut powder as energy sources in liquid culture medium. A new isoenzyme named Glac15 was identified, purified, and characterized. Glac15 possesses an optimum pH of 4.5 to 5.0 and a temperature range of 45°C to 55°C for the substrates tested. It was stable at pH values ranging from 5.0 to 7.0 and temperatures lower than 55°C, with more than 80% activity retained after incubation for 2 h. When used in bioethanol production process, 0.05 U/mL Glac15 removed 84% of the phenolic compounds in prehydrolysate, and the yeast biomass reached 11.81 (optimal density at 600 nm (OD600)), compared to no growth in the untreated one. Addition of Glac15 before cellulase hydrolysis had no significant effect on glucose recovery. However, ethanol yield were improved in samples treated with laccases compared to that in control samples. The final ethanol concentration of 9.74, 10.05, 10.11, and 10.81 g/L were obtained from samples containing only solid content, solid content treated with Glac15, solid content containing 50% prehydrolysate, and solid content containing 50% prehydrolysate treated with Glac15, respectively.

CONCLUSIONS

The G. lucidum laccase Glac15 has potentials in bioethanol production industry.

Induction, expression and characterisation of laccase genes from the marine-derived fungal strains Nigrospora sp. CBMAI 1328 and Arthopyrenia sp. CBMAI 1330

The capability of the fungi Nigrospora sp. CBMAI 1328 and Arthopyrenia sp. CBMAI 1330 isolated from marine sponge to synthesise laccases (Lcc) in the presence of the inducer copper (1–10 μM) was assessed. In a liquid culture medium supplemented with 5 μM of copper sulphate after 5 days of incubation, Nigrospora sp. presented the highest Lcc activity (25.2 U·L⁻¹). The effect of copper on Lcc gene expression was evaluated by reverse transcriptase polymerase chain reaction. Nigrospora sp. showed the highest gene expression of Lcc under the same conditions of Lcc synthesis. The highest Lcc expression by the Arthopyrenia sp. was detected at 96 h of incubation in absence of copper. Molecular approaches allowed the detection of Lcc isozymes and suggest the presence of at least two undescribed putative genes. Additionally, Lcc sequences from the both fungal strains clustered with other Lcc sequences from other fungi that inhabit marine environments.

Reversible covalent immobilization of Trametes villosa laccase onto thiolsulfinate-agarose: An insoluble biocatalyst with potential for decoloring recalcitrant dyes

The development of a solid-phase biocatalyst based on the reversible covalent immobilization of laccase onto thiol-reactive supports (thiolsulfinate-agarose [TSI-agarose]) was performed. To achieve this goal, laccase-producing strains isolated from Eucalyptus globulus were screened and white rot fungus Trametes villosa was selected as the best strain for enzyme production. Reduction of disulfide bonds and introduction of "de novo" thiol groups in partially purified laccase were assessed to perform its reversible covalent immobilization onto thiol-reactive supports (TSI-agarose). Only the thiolation process dramatically improved the immobilization yield, from 0% for the native and reduced enzyme to 60% for the thiolated enzyme. Mild conditions for the immobilization process (pH 7.5 and 4°C) allowed the achievement of nearly 100% of coupling efficiency when low loads were applied. The kinetic parameters, pH, and thermal stabilities for the immobilized biocatalyst were similar to those for the native enzyme. After the first use and three consecutives reuses, the insoluble derivative kept more than 80% of its initial capacity for decolorizing Remazol Brilliant Blue R, showing its suitability for color removal from textile industrial effluents. The possibility of reusing the support was demonstrated by the reversibility of enzyme-support binding.