The effect of fungal laccase on fractionated lignosulphonates (peritan Na)

Two fractions obtained after chromatography of lignosulphonates on Sephadex G-50, varying in M_rs, were treated with extracellular Trametes versicolor laccase. After incubation of the low M_r fraction, polymerization was observed, while in the case of the high M_r fraction the reverse process occurred. As a result of depolymerization, five new lower M_r fractions appeared. The reaction reached peak level after 2 hr of incubation and then the quantities of the products diminished, possibly due to their repolymerization. These studies indicate that laccase possesses both polymerization and depolymerization activity though the former was predominant.     

Alginate/carbon composite beads for laccase and glucose oxidase encapsulation: application in biofuel cell technology

Alginate–carbon beads were prepared in order to develop a biocompatible matrix for laccase and glucose oxidase immobilization for application in biofuel cell technology. The enzyme loading capacity was high (91%) in pure alginate beads for glucose oxidase. For laccase, the loading capacity was enhanced from 75% to 83% by introducing carbon. Desorption out of the matrix was controlled by the enzymes’ diffusion and reached a plateau after 40 h for laccase and 70 h for glucose oxidase. Two-thirds of both enzymes was irreversibly retained inside the alginate beads. This proportion increased to 80% for laccase in combined alginate/carbon beads. Half-life of the adsorbed enzyme was enhanced to 74 days for laccase in carbon/alginate beads and 45 days for glucose oxidase in pure alginate as compared to 38 days and 23 days for free enzymes, respectively.     

Mineralization and solubilization of synthetic lignin by manganese peroxidases from Nematoloma frowardii and Phlebia radiata

Crude and purified manganese peroxidase from the white-rot fungi Nematoloma frowardii and Phlebia radiata catalyzed the partial depolymerization of a [¹⁴C-ring]labelled synthetic lignin into water-soluble fragments (30–50%). The in vitro depolymerization of the ¹⁴C-labelled lignin was accompanied by a release of ¹⁴CO₂ ranging from 4 to 6%. Small quantities of the thiol mediator glutathione stimulated the depolymerization of lignin resulting in a mineralization and solubilization of up to 10 and 64%, respectively. Most of the water-soluble substances formed had molecular masses around 0.7 kDa, although a higher-molecular mass fraction was also detectable (>2 kDa). Photometric assays using 2,2′-azinobis(3-ethylbenzothiazolinesulphonate) as an indicator demonstrated that high levels of Mn(III), which were very probably responsible for the depolymerization and mineralization of the ¹⁴C-labelled lignin, were adjusted within the first 24 h of incubation. The manganese peroxidase catalyzed depolymerization process was not necessarily dependent on H₂O₂; also in the absence of the H₂O₂-generating system glucose/glucose oxidase, effective solubilization and mineralization of lignin dehydrogenation polymerizate occurred, due to the in part superoxide dismutase sensitive, ‘oxidase-like’ activity of MnP which probably produces radical species and peroxides from malonate.     

Comparison of the efficiency of bacterial and fungal laccases in delignification and detoxification of steam-pretreated lignocellulosic biomass for bioethanol production

This study evaluates the potential of a bacterial laccase from Streptomyces ipomoeae (SilA) for delignification and detoxification of steam-exploded wheat straw, in comparison with a commercial fungal laccase from Trametes villosa. When alkali extraction followed by SilA laccase treatment was applied to the water insoluble solids fraction, a slight reduction in lignin content was detected, and after a saccharification step, an increase in both glucose and xylose production (16 and 6%, respectively) was observed. These effects were not produced with T. villosa laccase. Concerning to the fermentation process, the treatment of the steam-exploded whole slurry with both laccases produced a decrease in the phenol content by up to 35 and 71% with bacterial and fungal laccases, respectively. The phenols reduction resulted in an improved performance of Saccharomyces cerevisiae during a simultaneous saccharification and fermentation (SSF) process, improving ethanol production rate. This enhancement was more marked with a presaccharification step prior to the SSF process.     

Depolymerization of low-rank coal by extracellular fungal enzyme systems. III.In vitro depolymerization of coal humic acids by a crude preparation of manganese peroxidase from the white-rot fungus Nematoloma frowardii b19

The in vitro depolymerization of humic acids derived from German lignite (low-rank coal, brown coal) was studied using a manganese peroxidase preparation from the white-rot fungus Nematoloma frowardii b19. The H₂O₂ required was continuously generated by glucose oxidase. Mn peroxidase depolymerized high-molecular-mass humic acids by forming fulvic-acid-like compounds. The depolymerization process was accompanied by the decolorization of the dark-brown humic acid fraction soluble in alkaline solutions (decrease in absorbance at 450 nm) and by the yellowish coloring of the fraction of acid-soluble fulvic-acid-like compounds (increase in absorbance at 360 nm). The Mn peroxidase of N. frowardii b19 has been proved to be highly stable; even after an in vitro reaction time of 7 days in the presence of humic acids, less than 10% loss in total oxidizing activity was detectable. Received: 16 September 1996 / Received revision: 16 December 1996 / Accepted: 20 December 1996     

Laccase in Anacardiaceae

The presence of a typical laccase is demonstrated in the cavities of the secretory ducts of a number of species of the Anacardiaceae, including Mangifera indica and Schinus molle. In addition mango fruit contains catechol oxidase. The presence of laccase may be of chemotaxonomic value.     

Purification and Characterization of Laccase from Chaetomium thermophilium and Its Role in Humification

Chaetomium thermophilium was isolated from composting municipal solid waste during the thermophilic stage of the process. C. thermophilium, a cellulolytic fungus, exhibited laccase activity when it was grown at 45°C both in solid media and in liquid media. Laccase activity reached a peak after 24 h in liquid shake culture. Laccase was purified by ultrafiltration, anion-exchange chromatography, and affinity chromatography. The purified enzyme was identified as a glycoprotein with a molecular mass of 77 kDa and an isoelectric point of 5.1. The laccase was stable for 1 h at 70°C and had half-lives of 24 and 12 h at 40 and 50°C, respectively. The enzyme was stable at pH 5 to 10, and the optimum pH for enzyme activity was 6. The purified laccase efficiently catalyzed a wide range of phenolic substrates but not tyrosine. The highest levels of affinity were the levels of affinity to syringaldazine and hydroxyquinone. The UV-visible light spectrum of the purified laccase had a peak at 604 nm (i.e., Cu type I), and the activity was strongly inhibited by Cu-chelating agents. When the hydrophobic acid fraction (the humic fraction of the water-soluble organic matter obtained from municipal solid waste compost) was added to a reaction assay mixture containing laccase and guaiacol, polymerization took place and a soluble polymer was formed. C. thermophilium laccase, which is produced during the thermophilic stage of composting, can remain active for a long period of time at high temperatures and alkaline pH values, and we suggest that this enzyme is involved in the humification process during composting.     

The effect of carbon source succession on laccase activity in the co-culture process of Ganoderma lucidum and a yeast

In the present paper, the mechanism of overproduction of laccase by microbe interaction was investigated in the co-culture process of Ganoderma lucidum and Candida sp. HSD07A. The results show that nitrogen source, sulfur source, hydrolytic enzymes and inducers do not have the significant influence on laccase activity, and glucose deprivation in the medium is also not the crucial reason why G. lucidum overproduces laccase although it can improve laccase activity at a certain extent. Furthermore, glucose deprivation is made by strain HSD07A, and NMR and GC data reveal that the yeast can convert glucose into glycerol and ethanol. G. lucidum cannot assimilate ethanol; however, glycerol is an efficient carbon source for G. lucidum. In the co-culture process, the appearance of the second carbon source, glycerol produced by the yeast, is the crucial reason why G. lucidum overproduces laccase because glycerol can make G. lucidum cells secrete more laccase by prolonging the secretion time under the condition of glucose deprivation. Thus, it is the carbon source succession in the co-culture process that leads to the overproduction of G. lucidum laccase.     

Bilirubin Oxidase Activity of Bacillus subtilis CotA

The spore coat protein CotA from Bacillus subtilis was previously identified as a laccase. We have now found that CotA also shows strong bilirubin oxidase activity and markedly higher affinity for bilirubin than conventional bilirubin oxidase. This is the first characterization of bilirubin oxidase activity in a bacterial protein.     

Overproduction of Trametes versicolor laccase by making glucose starvation using yeast

In the present paper, overproduction of laccase by microbe interaction was studied. When Trametes versicolor was co-cultured with Candida sp. HSD07A in submerged fermentation, laccase activity could be improved significantly and reached 10500 ± 160 U/l, 11.8 times more than that of the contrast group. Fermentation tests of the yeast indicated that it could produce amylase and cellulase, but couldn’t excrete laccase and the overproductive laccase was produced by T. versicolor; the interaction mechanism between T. versicolor and Candida sp. HSD07A was investigated and the results showed that amylase and cellulose could hydrolyze cell walls of T. versicolor; however, the degree of hydrolysis was at a very low level, could not lead to overproduction of laccase; glucose starvation state made by the yeast was the real reason why T. versicolor could overproduce laccase; moreover, this study also proved that making glucose starvation using the yeast was a novel and effective method.     

A novel membrane-surface liquid co-culture to improve the production of laccase from Ganoderma lucidum

In this work, a laccase producer, Ganoderma lucidum, was separated and identified according to its morphological characteristics and phylogenetic data. A 4000 U/l and 8500 U/l of laccase activity was obtained in 500 ml flask by submerged culture and biomembrane-surface liquid culture (BSLC), respectively. Furthermore, the novel biomembrane-surface liquid co-culture (BSLCc) was developed by adding Saccharomyces cerevisiae to reactor in order to shorten the fermentation period and improve laccase production. Laccase activity obtained by BSLCc, 23 000 U/l, is 5.8 and 2.7 times of that obtained by submerged culture and BSLC, respectively. In addition, laccase production by BSLCc was successfully scaled-up to 100 l reactor, and 38 000 U/l of laccase activity was obtained on day 8. The mechanism of overproducing laccase by BSLCc was investigated by metabolism pathway analysis of glucose. The results show glucose limitation in fermentation broth induces the secretion of laccase. The addition of S. cerevisiae, on one hand, leads to an earlier occurrence of glucose limitation state, and thus shortens the fermentation time; on the other hand, it also results in the appearance of a series of metabolites of the yeast including organic acids, ethanol, glycerol and so forth in fermentation broth, and both polyacrylamide gel electrophoresis analysis and enzyme activity detection of laccase show that these metabolites contribute to the improvement of laccase activity.     

Purification and Characterization of a Secreted Laccase of Gaeumannomyces graminis var. tritici

We purified a secreted fungal laccase from filtrates of Gaeumannomyces graminis var. tritici cultures induced with copper and xylidine. The active protein had an apparent molecular mass of 190 kDa and yielded subunits with molecular masses of 60 kDa when denatured and deglycosylated. This laccase had a pI of 5.6 and an optimal pH of 4.5 with 2,6-dimethoxyphenol as its substrate. Like other, previously purified laccases, this one contained several copper atoms in each subunit, as determined by inductively coupled plasma spectroscopy. The active enzyme catalyzed the oxidation of 2,6-dimethoxyphenol (K_m = 2.6 × 10⁻⁵ ± 7 × 10⁻⁶ M), catechol (K_m = 2.5 × 10⁻⁴ ± 1 × 10⁻⁵ M), pyrogallol (K_m = 3.1 × 10⁻⁴ ± 4 × 10⁻⁵ M), and guaiacol (K_m = 5.1 × 10⁻⁴ ± 2 × 10⁻⁵ M). In addition, the laccase catalyzed the polymerization of 1,8-dihydroxynaphthalene, a natural fungal melanin precursor, into a high-molecular-weight melanin and catalyzed the oxidation, or decolorization, of the dye poly B-411, a lignin-like polymer. These findings indicate that this laccase may be involved in melanin polymerization in this phytopathogen’s hyphae and/or in lignin depolymerization in its infected plant host.     

Purification and characterization of a secreted laccase of Gaeumannomyces graminis var. tritici.

We purified a secreted fungal laccase from filtrates of Gaeumannomyces graminis var. tritici cultures induced with copper and xylidine. The active protein had an apparent molecular mass of 190 kDa and yielded subunits with molecular masses of 60 kDa when denatured and deglycosylated. This laccase had a pI of 5.6 and an optimal pH of 4.5 with 2,6-dimethoxyphenol as its substrate. Like other, previously purified laccases, this one contained several copper atoms in each subunit, as determined by inductively coupled plasma spectroscopy. The active enzyme catalyzed the oxidation of 2, 6-dimethoxyphenol (Km = 2.6 x 10(-5) +/- 7 x 10(-6) M), catechol (Km = 2.5 x 10(-4) +/- 1 x 10(-5) M), pyrogallol (Km = 3.1 x 10(-4) +/- 4 x 10(-5) M), and guaiacol (Km = 5.1 x 10(-4) +/- 2 x 10(-5) M). In addition, the laccase catalyzed the polymerization of 1, 8-dihydroxynaphthalene, a natural fungal melanin precursor, into a high-molecular-weight melanin and catalyzed the oxidation, or decolorization, of the dye poly B-411, a lignin-like polymer. These findings indicate that this laccase may be involved in melanin polymerization in this phytopathogen's hyphae and/or in lignin depolymerization in its infected plant host.     

Purification and characterization of a novel laccase from Coprinus cinereus and decolorization of different chemically dyes

Laccase is a blue copper oxidase with multiple copper ions and widely distributed in higher plant and fungi. To date, numerous fungal laccases have been reported by many researchers. In present work, a new laccase gene, named CcLCC5I, from Coprinus cinereus was synthesized chemically according to the yeast bias codon and integrated into Pichia pastoris GS115 genome by electroporation. SDS-PAGE analysis showed that the recombinant laccase has a molecular mass of approximately 56.8 kDa. Its biochemical properties was carried out using substrate 2-2^′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS). It was showed that the optimum pH and temperature of the laccase is 3.0 and 55 °C, respectively. Except for copper ions, most metal ions inhibited the laccase activity at a high concentration about 10 mM. Sodium sulfite can also highly inhibit laccase activity whereas EDTA had no inhibitory effect on the laccase activity. The CcLCC5I have high ability to decolor not only azo but also aryl methane dyes. The recombinant laccase decolored 44.6 % orange G, 54.8 % Crystal Violet, and 87.2 % Malachite green at about 2.6 h. The novel laccase may be a good candidate for breeding engineering strains used in the treatment of industrial effluent containing azo and aryl methane dyes.     

Semi-continuous production of laccase byPhlebia radiata in different culture media

The white-rot fungusPhlebia radiata, immobilized on a polypropylene carrier, was cultivated in a laboratory fermentor under semi-continuous conditions on culture media varying in the content of nitrogen, glucose, vitamins and microelements. Moreover, two laccase inducers were used: veratryl alcohol and veratraldehyde. Throughout the cultivation except the growth phase in the first cycle of fermentation, the observed rate of laccase expression reached up to about 2.0 nkat/mL per 1 h of cultivation, as determined by ABTS oxidation. In most experiments, phenol oxidase activity was determined also in the reaction with syringaldazine, giving reaction rates almost two times lower than in the case of ABTS.     

Purification of pyranose oxidase from the white rot fungus Irpex lacteus and its cooperation with laccase in lignin degradation

Laccase and peroxidases mainly cause polymerization of lignin in vitro due to the random coupling of the phenoxy radicals or quinoid intermediates. White rot fungi may avoid polymerization in vivo by reduction of these intermediates. Pyranose oxidase is suggested to play such a role based on its quinone-reducing activity, but direct evidence has been lacking. In this study, a pyranose oxidase was purified from the white rot fungus Irpex lacteus and partially characterized. The enzyme is composed of four subunits of 71 kDa as determined by SDS-PAGE. It exhibits maximum activity at pH 6.5 and 55 °C and is rather stable. d-glucose is the preferred substrate, but d-galactose, l-sorbose and d-xylose are also readily oxidized. In addition to O₂, the enzyme can also transfer electrons to various quinones and the ABTS [2,2′-azinobis(3-ethylbenzthiazoline-6-sulfonic acid)] cation radical. Laccase-generated quinoids are also reduced by the enzyme. Four different technical lignins were treated with laccase with and without pyranose oxidase. Subsequent gel permeation chromatography analysis demonstrated that the pyranose oxidase efficiently inhibited the polymerization of lignin caused by laccase and even brought about degradation.     

Oxidation of galactomannan by laccase plus TEMPO yields an elastic gel

Chemical modifications of galactomannans are applied to improve and/or modify their solubility, rheological and functional properties, but have limited specificity and are often difficult to control. Enzymatic reactions, catalyzed under mild process conditions, such as depolymerization, debranching and oxidation, represent a viable and eco-friendly alternative. In this study, we describe oxidation of guar galactomannan primary hydroxyl groups by a fungal laccase using the stable radical TEMPO as mediator. Four fungal laccases were investigated from: Trametes versicolor, Myceliophthora thermophila, Thielavia arenaria, Cerrena unicolor. The laccase from T. versicolor was found to efficiently oxidize TEMPO and to be free of mannanase side activity. Oxidation of galactomannan with this enzyme plus TEMPO brought about a ten-fold increase in viscosity of a guar galactomannan solution and altered its rheological profile, by converting a viscous polysaccharide solution into an elastic gel. This structural modification is presumably due to formation of inter-chain hemiacetalic bonds between newly generated carbonyl groups and free OH groups, yielding a cross-linked gel. These findings could be of practical importance, considering that polysaccharides with high viscosity, gelling and elastic properties can find interesting and novel applications as thickeners, viscosifiers and emulsion stabilizers in several industrial applications such as: personal care, oil operations, paper coating, paints, construction and mining.     

Removal of type 2 Cu from ascorbate oxidase and laccase by reaction with n,n-diethyldithiocarbamate

The type 2 Cu of ascorbate oxidase from zucchini peelings can be rapidly removed by reaction with a tenfold excess N,N-diethyldithiocarbamate (DDC) in air, while other chelating agents, such as EDTA, require anaerobic reducing conditions. The type 2 Cu of laccase from Rhus vernicifera is never removed under aerobic conditions. In anaerobiosis and in the presence of a reducing agent, EDTA is also unable to remove the copper unless a smaller lipophilic molecule (DDC or dimethylglyoxime) is present, acting as a mediator. Type 1 Cu is not involved in the reaction of ascorbate oxidase with DDC, but reduction of type 3 Cu is probably required for type 2 Cu depletion, suggesting interdependence of type 2 and type 3 copper. Type 2 Cu is less exposed in laccase, possibly because of the large carbohydrate content of this protein.     

Extracellular oxidases and the transformation of solubilised low-rank coal by wood-rot fungi

The involvement of extracellular oxidases in biotransformation of low-rank coal was assessed by correlating the ability of nine white-rot and brown-rot fungi to alter macromolecular material in alkali-solubilised brown coal with the spectrum of oxidases they produce when grown on low-nitrogen medium. The coal fraction used was that soluble at 3.0?pH?6.0 (SWC6 coal). In 15-ml cultures, Gloeophyllum trabeum, Lentinus lepideus and Trametes versicolor produced little or no lignin peroxidase, manganese (Mn) peroxidase or laccase activity and caused no change to SWC6 coal. Ganoderma applanatum and Pycnoporus cinnabarinus also produced no detectable lignin or Mn peroxidases or laccase yet increased the absorbance at 400?nm of SWC6 coal. G. applanatum, which produced veratryl alcohol oxidase, also increased the modal apparent molecular mass. SWC6 coal exposed to Merulius tremellosus and Perenniporia tephropora, which secreted Mn peroxidases and laccase and Phanerochaete chrysosporium, which produced Mn and lignin peroxidases was polymerised but had unchanged or decreased absorbance. In the case of both P. chrysosporium and M. tremellosus, polymerisation of SWC6 coal was most extensive, leading to the formation of a complex insoluble in 100?mM NaOH. Rigidoporus ulmarius, which produced only laccase, both polymerised and reduced the A ₄₀₀ of SWC6 coal. P. chrysosporium, M. tremellosus and P. tephropora grown in 10-ml cultures produced a spectrum of oxidases similar to that in 15-ml cultures but, in each case, caused more extensive loss of A ₄₀₀, and P. chrysosporium depolymerised SWC6 coal. It is concluded that the extracellular oxidases of white-rot fungi can transform low-rank coal macromolecules and that increased oxygen availability in the shallower 10-ml cultures favours catabolism over polymerisation.     

A study of a series of recombinant fungal laccases and bilirubin oxidase that exhibit significant differences in redox potential,substrate specificity,and stability

A series of fungal laccases (Polyporus pinsitus, Rhizoctonia solani, Myceliophthora hermophila, Scytalidium thermophilum) and one bilirubin oxidase (Myrothecium verrucaria) have been studied to determine their redox potential, specificity, and stability. Polyporus and Rhizoctonia laccases possess potentials near 0.7–0.8 V (vs. NHE), while other oxidases have potentials near 0.5 V. It is observed that higher redox potential correlates with higher activity. By EPR, no significant change in the geometry of type 1 copper (II) site is observed over this series. At the optimal pH, the two substrates studied, 2,2′-azinobis-(3-ethylbenzthiazoline-6-sulfonic acid) and syringaldazine, show K_m values ranging from 10 to 120 and from 1 to 45 μM; and k_cat values ranging from 50 to 16000 and 200 to 3000 per min, respectively. The enzymes are more stable in the neutral-alkaline pH range. The thermal stability is in the order of bilirubin oxidase ≈ Myceliophthora laccase ≈ Scytalidium laccase > Polyporus laccase > Rhizoctonia laccase. Based on these results and the sequence alignments made against Zucchini ascorbate oxidase it is speculated that structural differences in the substrate-activation site (a ‘blue’, type 1 copper center) control the redox potential range as well as substrate specificity, and the cystine content contributes to stability.