Biodegradation and reduction of toxicity of Azo Trypan Blue dye by Amazonian strains of gasteroid fungi (Basidiomycota)

Amazonian strains of Cyathus spp. and Geastrum spp. were studied for the ability to discolor the trypan blue azo dye and reduce its toxicity. Discoloration of trypan blue dye (0.05%) was evaluated in solid and aqueous medium over different periods. The reduction of dye toxicity after treatment was assessed by seed germination and the development of lettuce seedlings (Lactuca sativa L.) and toxicity test in Artemia salina (L.) larvae. All evaluated strains showed the potential to reduce the color intensity of trypan blue dye. Cyathus strains reached 96% discoloration, and C. albinus and C. limbatus also reduced dye toxicity. Geastrum strains showed a high efficiency degree in color reduction, reaching 98% discoloration, however, the by-products generated during the process presented toxicity and require further investigation. For the first time, Amazonian strains of gasteroid fungi degrading trypan blue are reported, some even reducing its toxicity. Thus, making them promising sources of enzymes of interest to bioremediation scenarios involving synthetic dyes.

Secretory Laccase from Pestalotiopsis Species CDBT-F-G1 Fungal Strain Isolated from High Altitude: Optimization of Its Production and Characterization

Microorganisms producing laccases may be used for the pretreatment of lignocellulosic biomass to recover fermentable sugar. Very few fungi and other microbes growing in high altitudes have been tested for this purpose. As part of this study, we have collected soil samples from different parts of the Kathmandu Valley and the Rautah at district of Nepal (1600 to 2303 m above sea level) and successfully cultured 53 different isolates of microorganisms. Among the 53 isolates obtained 30 were Actinomycetes, 20 were Streptomycetes, and three were fungi). These isolates were tested for laccase expression using guaiacol, tannic acid, and 1-naphthol as substrates. Twelve of the 53 isolates tested positive for the expression of laccase. Among the laccase- positive isolates, a fungal species designated as CDBT-F-G1was found to produce high levels of laccase. This isolate was identified as Pestalotiopsis species based on 18S rRNA sequencing. Pestalotiopsis spp. CDBT-F-G1 isolate grows efficiently in PDB media containing 1% Kraft lignin at pH 5 and 30 °C and secretes 20 ± 2 U/mL laccase in culture medium. Further optimization of growth conditions reveled that addition of (i) metal salts, e.g., 1 mM magnesium sulfate (51 ± 25 U/mL); (ii) agitation of cultures at 200 rpm (51 ± 9U/mL); (iii) surfactants, e.g., 0.75 mM Tween 80 (54 ± 14 U/mL); (iv) 40% dissolved O2 (57 ± 2 U/mL) and inducers, e.g., 1 mM gallic acid (69 ± 11 U/mL), further promote laccase production by Pestalotiopsis spp. CDBT-F-G1 isolate. On the other hand, 0.1 mM cysteine inhibited laccase production. The secretory laccase obtained from fermentation broth of CDBT-F-G1 was partially purified by ammonium sulfate (13-fold purification with specific activity 26,200 U/mg) and acetone (14-fold purification with specific activity 31,700 U/mg) precipitation methods. The enzyme has an approximate molecular mass of 43 kDa, pH and temperature optima werepH6 and 60 °C, respectively. Vmax and Km were 100 μmol/min and 0.10 mM, respectively, with ABTS as the substrate. Given the above characteristics, we believe Pestalotiopsis spp. CDBT-F-G1 strain native to high altitudes of Nepal could be used to pretreat lignocellulosic biomass to efficiently recover fermentable sugars.

Induction of laccase activity in the white rot fungus Pleurotus ostreatus using water polluted with wheat straw extracts

The purpose of this work was to explore the use of polluted water effluents from wheat straw using industries as inducers of lignocellulolytic enzymatic activities in cultures of white rot basidiomycetes. For this purpose, we studied the effect of a wheat straw water extract on the evolution of the laccase activity recovered from submerged cultures of Pleurotus ostreatus made in different media and under various culture conditions. Our results demonstrated an accumulative induction effect in all the cultures and conditions tested. This induction is parallel to changes in the laccase electrophoretic profiles recovered from the culture supernatants. The isoenzyme that appeared to be mainly responsible for the laccase activity under these conditions was laccase 10, as confirmed by sequencing the induced protein. These results support the idea of using wheat straw effluents as inducers in liquid cultures of P. ostreatus mycelia for the production of ligninolytic enzymatic cocktails.

Proteomic analysis of Fusarium solani isolated from the Asian longhorned beetle, Anoplophora glabripennis

Wood is a highly intractable food source, yet many insects successfully colonize and thrive in this challenging niche. Overcoming the lignin barrier of wood is a key challenge in nutrient acquisition, but full depolymerization of intact lignin polymers has only been conclusively demonstrated in fungi and is not known to occur by enzymes produced by insects or bacteria. Previous research validated that lignocellulose and hemicellulose degradation occur within the gut of the wood boring insect, Anoplophora glabripennis (Asian longhorned beetle), and that a fungal species, Fusarium solani (ATCC MYA 4552), is consistently associated with the larval stage. While the nature of this relationship is unresolved, we sought to assess this fungal isolate's ability to degrade lignocellulose and cell wall polysaccharides and to extract nutrients from woody tissue. This gut-derived fungal isolate was inoculated onto a wood-based substrate and shotgun proteomics using Multidimensional Protein Identification Technology (MudPIT) was employed to identify 400 expressed proteins. Through this approach, we detected proteins responsible for plant cell wall polysaccharide degradation, including proteins belonging to 28 glycosyl hydrolase families and several cutinases, esterases, lipases, pectate lyases, and polysaccharide deacetylases. Proteinases with broad substrate specificities and ureases were observed, indicating that this isolate has the capability to digest plant cell wall proteins and recycle nitrogenous waste under periods of nutrient limitation. Additionally, several laccases, peroxidases, and enzymes involved in extracellular hydrogen peroxide production previously implicated in lignin depolymerization were detected. In vitro biochemical assays were conducted to corroborate MudPIT results and confirmed that cellulases, glycosyl hydrolases, xylanases, laccases, and Mn- independent peroxidases were active in culture; however, lignin- and Mn- dependent peroxidase activities were not detected While little is known about the role of filamentous fungi and their associations with insects, these findings suggest that this isolate has the endogenous potential to degrade lignocellulose and extract nutrients from woody tissue.

Secrets of the subterranean pathosystem of Armillaria

Armillaria root disease affects fruit and nut crops, timber trees and ornamentals in boreal, temperate and tropical regions of the world. The causal pathogens are members of the genus Armillaria (Basidiomycota, Physalacriaceae). This review summarizes the state of knowledge and highlights recent advances in Armillaria research.

TAXONOMY

Armillaria includes more than 40 morphological species. However, the identification and delineation of species on the basis of morphological characters are problematic, resulting in many species being undetected. Implementation of the biological species' concept and DNA sequence comparisons in the contemporary taxonomy of Armillaria have led to the discovery of a number of new species that are not linked to described morphological species.

HOST RANGE

Armillaria exhibits a range of symbioses with both plants and fungi. As plant pathogens, Armillaria species have broad host ranges, infecting mostly woody species. Armillaria can also colonize orchids Galeola and Gastrodia but, in this case, the fungus is the host and the plant is the parasite. Similar to its contrasting relationships with plants, Armillaria acts as either host or parasite in its interactions with other fungi. Disease control: Recent research on post-infection controls has revealed promising alternatives to the former pre-plant eradication attempts with soil fumigants, which are now being regulated more heavily or banned outright because of their negative effects on the environment. New study tools for genetic manipulation of the pathogen and characterization of the molecular basis of the host response will greatly advance the development of resistant rootstocks in a new stage of research. The depth of the research, regardless of whether traditional or genomic approaches are used, will depend on a clear understanding of where the different propagules of Armillaria attack a root system, which of the pathogen's diverse biolymer-degrading enzymes and secondary metabolites facilitate infection, and how the course of infection differs between resistant and susceptible hosts.

Studies on the Pycnoporus sanguineus CCT-4518 laccase purified by hydrophobic interaction chromatography

A laccase from Pycnoporus sanguineus was purified by two steps using phenyl-Sepharose columm. A typical procedure provided 54.1-fold purification, with a yield of 8.37%, using syringaldazine as substrate. The molecular weight of the purified laccase was 69 and 68 kDa as estimated by 12% (w/v) SDS-PAGE gel and by gel filtration, respectively. The K (m) values for the substrates ABTS, syringaldazine, and guaiacol were 58, 8.3, and 370 muM, respectively. The enzyme's pH optimum for syringaldazine was 4.2 and optimal activity was 50 degrees C. The enzyme showed to be thermostable because when kept at 50 degrees C for 24 and 48 h it retained 93 and 76% activity. This laccase was inhibited by L: -cysteine, beta-mercaptoethanol, NaN(3), NaF, and HgCl(2).

Fungal laccases – occurrence and properties

Laccases of fungi attract considerable attention due to their possible involvement in the transformation of a wide variety of phenolic compounds including the polymeric lignin and humic substances. So far, more than a 100 enzymes have been purified from fungal cultures and characterized in terms of their biochemical and catalytic properties. Most ligninolytic fungal species produce constitutively at least one laccase isoenzyme and laccases are also dominant among ligninolytic enzymes in the soil environment. The fact that they only require molecular oxygen for catalysis makes them suitable for biotechnological applications for the transformation or immobilization of xenobiotic compounds.

Biochemical characterization and molecular evidence of a laccase from the bird’s nest fungus Cyathus bulleri

Cyathus bulleri, a bird's nest fungus, known to decolorize polymeric dye Poly R-478, was found to produce 8 U ml(-1) of laccase in malt extract broth. Laccase activity appeared as a single band on non-denaturing gel. Laccase was purified to homogeneity by anion exchange chromatography and gel filtration. The enzyme was a monomer with an apparent molecular mass of 60 kD, pI of 3.7 and was stable in the pH range of 2-6 with an optimum pH of 5.2. The optimal reaction temperature was 45 degrees C and the enzyme lost its activity above 70 degrees C. Enzyme could oxidize a broad range of various phenolic substrates. K(m) values for ABTS, 2,6-dimethoxyphenol, guaiacol, and ferulic acid were found to be 48.6, 56, 22, and 14 mM while K(cat) values were 204, 180, 95.6, and 5.2, respectively. It was completely inhibited by KCN, NaN(3), beta-mercaptoethanol, HgCl(2), and SDS, while EDTA had no effect on enzyme activity. The N-terminal amino acid sequence of C. bulleri laccase showed close homology to N-terminal sequences of laccase from other white-rot fungi. A 150 bp gene sequence encoding copper-binding domains I and II was most similar to the sequence encoding a laccase from Pycnoporus cinnabarinus with 74.8% level of similarity.

Purification and characterization of laccase-1 from Pleurotus florida

Pleurotus florida (ITCC 3308) produces two laccase enzymes (L1 and L2) in potato-dextrose media containing 0.5% yeast extract. Concentrated culture filtrate was separated on DEAE-Sephadex (A-50) column into two enzyme peaks, subsequently named L1 and L2. The L1 enzyme has been purified to homogeneity by ion-exchange and gel-permeation chromatography. L1 is a monomeric glycoprotein with a molar mass of 77 and 82 kDa as determined by SDS-PAGE and gel-filtration chromatography, respectively. The pI value of L1 has been determined to be 4.1. The optimum reaction temperature of the enzyme is 50 degrees C. The Km and some other kinetic parameters of L1 have been determined. Cyanide and azide completely inhibit the enzyme activity. The enzyme was fully active in 1:1 (V/V) buffer-chloroform for at least 2 h. Spectroscopic analysis revealed that the enzyme has four copper atoms, a type 1 copper, a type 2 copper and a type 3 binuclear copper.

Laccase isoenzymes of Pleurotus eryngii: characterization, catalytic properties, and participation in activation of molecular oxygen and Mn2+ oxidation

Two laccase isoenzymes produced by Pleurotus eryngii were purified to electrophoretic homogeneity (42- and 43-fold) with an overall yield of 56.3%. Laccases I and II from this fungus are monomeric glycoproteins with 7 and 1% carbohydrate content, molecular masses (by sodium dodecyl sulfate-polyacrylamide gel electrophoresis) of 65 and 61 kDa, and pIs of 4.1 and 4.2, respectively. The highest rate of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) oxidation for laccase I was reached at 65 degrees C and pH 4, and that for laccase II was reached at 55 degrees C and pH 3.5. Both isoenzymes are stable at high pH, retaining 60 to 70% activity after 24 h from pH 8 to 12. Their amino acid compositions and N-terminal sequences were determined, the latter strongly differing from those of laccases of other basidiomycetes. Antibodies against laccase I reacted with laccase II, as well as with laccases from Pleurotus ostreatus, Pleurotus pulmonarius, and Pleurotus floridanus. Different hydroxy- and methoxy-substituted phenols and aromatic amines were oxidized by the two laccase isoenzymes from P. eryngii, and the influence of the nature, number, and disposition of aromatic-ring substituents on kinetic constants is discussed. Although both isoenzymes presented similar substrate affinities, the maximum rates of reactions catalyzed by laccase I were higher than those of laccase II. In reactions with hydroquinones, semiquinones produced by laccase isoenzymes were in part converted into quinones via autoxidation. The superoxide anion radical produced in the latter reaction dismutated, producing hydrogen peroxide. In the presence of manganous ion, the superoxide union was reduced to hydrogen peroxide with the concomitant production of manganic ion. These results confirmed that laccase in the presence of hydroquinones can participate in the production of both reduced oxygen species and manganic ions.

Production and Characterization of a Monoclonal Antibody Raised Against Surface Antigens from Mycelium of Gaeumannomyces graminis var. tritici: Evidence for an Extracellular Polyphenol Oxidase

ABSTRACT A murine monoclonal antibody (MAb) of immunoglobulin class M (IgM) was raised against surface antigens from Gaeumannomyces graminis var. tritici and, by enzyme-linked immunosorbent assay, recognized isolates of G. graminis var. tritici, G. graminis var. avenae and G. graminis var. graminis. Characterization of the antigen by heat and protease treatments showed that the epitope recognized by the MAb was a protein. Antigen production was detected only in live mycelia. Immunofluorescence studies showed that the antigen was associated with both the broad melanized macrohyphae and hyaline mycelia of G. graminis var. tritici. Secretion of antigen into an aqueous minimal medium was promoted only by exposure of live mycelia to certain phenolic substrates, including monophenols ortho-, para-, and meta-cresol; 3,4,5-trihydroxybenzoic acid (gallic acid); and phenolic amino acid L-3-(3,4-dihydroxyphenyl) alanine (L-DOPA). Antigen secretion was not promoted by 3-(4-hydroxyphenyl) alanine (L-tyrosine). The MAb reacted strongly with purified enzyme laccase (polyphenol oxidase, EC 1.10.3.2) but did not recognize purified tyrosinase (monophenol oxidase, EC 1.14.18.1). Moreover, chemicals that bind to copper and inhibit copper-containing enzymes such as laccase completely inhibited antigen secretion in response to L-DOPA. The MAb was tested for specificity against a wide range of fungi, common yeast species, and gram positive and negative bacteria. It did not recognize antigens from a broad range of unrelated fungi, including Gliocladium roseum, Fusarium sp., Phoma exigua, Phialophora fastigiata, Penicillium crustosum, Pythium ultimum, Rhizopus stolonifer, Rhizoctonia carotae, R. oryzae, R. tuliparum, and Trichoderma viride, nor did it recognize surface antigens from yeasts or bacteria. The MAb cross-reacted with antigens from Botrytis spp., Chaetomium globosum, R. cerealis, and R. solani. However, secretion of antigen by R. solani and R. cerealis was not promoted by L-DOPA, and secretion by C. globosum in response to the phenolic amino acid was significantly less compared to G. graminis var. tritici.

Oxidation of phenols, anilines, and benzenethiols by fungal laccases: correlation between activity and redox potentials as well as halide inhibition

A comparative study has been performed with several fungal laccases for the oxidation of a series of phenols, anilines, and benzenethiols and for the inhibition by halides. The observed K(m) and kcat were correlated to the structure of substrate. The change in log (kcat/K(m)) was found to be proportional to the one-electron redox potential difference between laccase's type 1 copper site and substrate. This correlation indicated that the first electron transfer from substrate to laccase was governed by the "outersphere" mechanism. Compared to the electronic factor, the steric effect of small o-substituents (such as methyl and methoxy groups) was found to be unimportant. The depth of the laccase's type 1 copper site was estimated as approximately 10 A by comparing the steric effect among five 2-methoxyphenols whose 4-substituents ranged from 0.1 to 14 kDa in mass. The observed inhibition potency order of F- > Cl- > Br- was attributed to limited accessibility of laccase's type 2/type 3 trinuclear copper cluster site. Although the enzymes studied have homologous primary sequences and predicted similar backbone structures, the difference exhibited by each enzyme (in interacting with individual substrate or inhibitor) suggested the structural variation in their functional domains.

The identification and characterization of four laccases from the plant pathogenic fungus Rhizoctonia solani

Four distinct laccase genes, lcc1, lcc2, lcc3 and lcc4, have been identified in the fungus Rhizoctonia solani. Both cDNA and genomic copies of these genes were isolated and characterized. Hybridization analyses indicate that each of the four laccase genes is present in a single copy in the genome. The R. solani laccases can be divided into two groups based on their protein size, intron/exon organization, and transcriptional regulation. Three of these enzymes have been expressed in the fungus Aspergillus oryzae. Two of the recombinant laccases, r-lcc1 and r-lcc4, as well as the native lcc4 enzyme were purified and characterized. The purified proteins are homodimeric, comprised of two subunits of approximately 66kDa for lcc4 and 50-100kDa for the recombinant lcc1 protein. These laccases have spectral properties that are consistent with other blue copper proteins. With syringaldazine as a substrate, lcc4 has optimal activity at pH7, whereas lcc1 has optimal activity at pH6.

Production and Characterization of Laccase from Botrytis cinerea 61-34

An isolate of Botrytis cinerea (strain 61-34) constitutively expresses substantial amounts of extracellular laccase on a defined growth medium. The enzyme has been purified to homogeneity by a facile operational sequence, the last stage of which involves hydrophobic interaction chromatography. By these means, over 80 mg of laccase liter(sup-1) can be obtained from aerated fermentor reaction broths. The enzyme, with an estimated M(infr) of 74,000 and pI of 4.0, is a monomeric glycoprotein containing 49% carbohydrate predominantly as hexose. With 2,6-dimethoxyphenol, it exhibits a pH optimum of 3.5 and a temperature optimum of 60(deg)C, and its K(infm) is 100 (mu)M. The purified enzyme with this substrate has a specific activity of 9.1 mkat mg of protein(sup-1). Taken together with a broad substrate range and its stability in 4% sodium dodecyl sulfate or 2 M urea solutions, several biotechnology transfers are suggested.