Rigidoporus Lignosus Research Articles

Molecular phylogeny of Rigidoporus microporus isolates associated with white rot disease of rubber trees (Hevea brasiliensis)

Rigidoporus microporus (Polyporales, Basidiomycota) syn. Rigidoporus lignosus is the most destructive root pathogen of rubber plantations distributed in tropical and sub-tropical regions. Our primary objective was to characterize Nigerian isolates from rubber tree and compare them with other West African, Southeast Asian and American isolates. To characterize the 20 isolates from Nigeria, we used sequence data of the nuclear ribosomal DNA ITS and LSU, β-tubulin and translation elongation factor 1-α (tef1) gene sequences. Altogether, 40 isolates of R. microporus were included in the analyses. Isolates from Africa, Asia and South/Central America formed three distinctive clades corresponding to at least three species. No phylogeographic pattern was detected among R. microporus collected from West and Central African rubber plantations suggesting continuous gene flow among these populations. Our molecular phylogenetic analysis suggests the presence of two distinctive species associated with the white rot disease. Phylogenetic analyses placed R. microporus in the Hymenochaetales in the vicinity of Oxyporus. This is the first study to characterize R. microporus isolates from Nigeria through molecular phylogenetic techniques, and also the first to compare isolates from rubber plantations in Africa and Asia.

Isolation of Rigidoporus microporus, the Cause of WRD of Rubber, from Some Forest Associated Plants

Natural rubber while promoting export earnings and livelihood of people supplementthousands of hectares to the forest cover. Over the past decades, the rubber yield hassignificantly increased due to the cultivation of high yielding clones. However, latexproduction still faces serious economic losses due to many biotic constraints which includesignificant losses caused by pathogenic fungi. Among them, White root disease (WRD) isvery destructive in rubber plantations of Sri Lanka and in many other rubber growingcountries. This disease has been identified as one of the major causes for the loss of plantsduring the first five years after planting resulting in low productivity levels. Inspite of the factthat disease management strategies have been clearly outlined by the Rubber ResearchInstitute, the disease incidence is showing an increasing trend. One of the main reasons forthis has been identified as the increment of the host range. In this situation expansion of thehost range of R.micrporus was undertaken. R. microporus was isolated from the symptomatichost plants such as Mucuna bractiacta, Camellia sinensis, Cinnamomum zeylanicum,Artocarpus nobilis, Alstonia macrophyll growing in and around rubber plantations. Some ofthe above crops such as C. sinensis, C. zeylanicum are intercrops recommended by the RRIwhile A. nobilis and A. macrophylla are important forest crop species grown in the vicinity ofrubber cultivations. M. bractiata is also one of the most commonly grown cover cropsrecommended for rubber plantations. The pathogen was isolated, on to Malt Extract Agarafter surface sterilizing in 70% ethanol for 3 minutes. Pure cultures were obtained and thecultural characteristics were recorded for the five isolates separately. For comparativepurpose isolate from H. brasiliensis was employed. Colonies showed white flattened cultures.Isolates from M. bractiacta, C. sinensis, C. zeylanicum, H. brsiliensis and A. nobilis showedpuffy aerial growth while A. macrophylla showed clear concentric zones which are prominentfrom the lower side of the colonies. Among the isolates investigated, the fastest growth ratewas observed in the isolate from C. sinensis showing 1.262cm/day while the lowest growthrate 1.205 cm/day was shown by the rubber isolate. The pathogenecity of the isolatesobtained from the above hosts were proven against the respective hosts by following theKoch’s postulates under green house conditions. The cross infection abilities of the isolateswere also assessed and all isolates infected Hevea brasiliensis showing cross infectionabilities. Pathogenic and genetic variability among the different isolates are beinginvestigated.The information will be valuable in the development of improved managementstrategies against white root disease of rubber.

Bioantifungal Activity of Selected Medicinal Plant Extracts against Root Rot of Fungal Disease

Root rot disease of fungal such as Ganoderma philippii, Phellinus noxius and Rigidoporus microporus are well known destructive fungus to plant root. The in vitro antifungal screening of selected medicinal plants was studied against the disease. The twelve of Malaysian medicinal plants including the leaves of Aglaia argentea, A. leucophylla, A. grandis, A. odorata, A. odoratissima, A. varrisquama, Alium sativum (bulbs) and Cassia alata, Catharanthus roseus stems and leaves, Derris elliptica leaves and Tinospora baenzigeri stems were extracted using different types of solvents extraction i.e, dichloromethane (DCM), acetone and methanol at the concentration of 20 mg/mL. The extracts were studied for antifungal activities against three species of fungal disease including G. Philippii, P. noxius and R. microporus. The antifungal activities of the extracts were determined by the presence or absence of fungal inhibition zone growth on Potato dextrose agar (PDA). The extracts shows a significant results but varying in their antifungal activities on the selected fungal. The DCM and acetone extracts of C. roseus stems had the highest antifungal activities against R. microporus fungus compared to methanolic extract. On the other hand, acetone extracts of A. argentea leaves also gave the highest antifungal activities against G. philippii compared to other extracts. However, all of the extracts didn’t show any inhibition zone on P. noxius culture. In general, the DCM extracts of C. roseus stems contain the most of bio-antifungal of active compounds against R. microporus of fungal disease.

Kinetic role of a histidine residue in the T1 copper site of the laccase from Rigidoporus lignosus

Laccases (benzendiol:oxygen oxidoreductases; EC 1.10.3.2) catalyze the oxidation of a broad range of substrates, such as polyphenols, dyes and pollutants, and thus these enzymes are widely applied in industrial, biotechnological and environmental fields. In order to improve their biotechnological applications, a deep knowledge of structural factors involved in controlling their activity, in various experimental conditions and on different substrates, is required. In the present study, a laccase from the mushroom Rigidoporus lignosus was kinetically characterized. In particular, the stability, the effects of pH, ionic strength and fluoride ion concentration on the kinetic parameters were investigated, using three di-hydroxy-benzene isomers (1,2-dihydroxy-benzene, 1,3-dihydroxy-benzene and 1,4-dihydroxy-benzene) as substrates. The catalytic constant values of the laccase showed a bell-shaped pH profile, with the same optimum pH and pKa values for all tested substrates. This behavior appears to be due to the presence of an ionizable residue in the enzyme active site. To identify this residue, the enzyme was derivatized with diethyl-pyrocarbonate to modify accessible histidine residues, which, according to structural data, are present in the active site of this enzyme. The kinetic behavior of the derivatized laccase was compared with that of the native enzyme and the derivatized residues were identified by mass spectrometry. Mass spectrometry and kinetic results suggest the main role of His-457 in the control of the catalytic activity of laccase from R. lignosus.

Recombinant Laccase: I. Enzyme cloning and characterization

We obtained structural and functional characterization of a recombinant Laccase from Rigidoporus lignosus (formerly Rigidoporus microporus), a white-rot basidiomycete, by means of circular dichroism (CD) spectra, cyclic voltammetry (CV) and biochemical assays. Here we report the optimization of expression and purification procedures of a recombinant Laccase expressed in supercompetent Escherichia coli cells. We amplified the coding sequence of Laccase using PCR from cDNA and cloned into a bacterial expression system. The resulting expression plasmid, pET-28b, was under a strong T7/Lac promoter induced by IPTG (isopropyl-β-d-thiogalactoipyranoside). We obtained purification by fast protein liquid chromatography (FPLC) method. We recorded the variation of the current of a solution containing purified Laccase with increasing Syringaldazine (SGZ) concentration using a potentiometer as proof of principle, showing its compatibility with the development of a new enzymatic biosensor for medical purposes, as described in Part II.

In Silico and in Vitro Physicochemical Screening of Rigidoporus sp. Crude Laccase-assisted Decolorization of Synthetic Dyes—Approaches for a Cost-effective Enzyme-based Remediation Methodology

The objective of this paper is to compare in silico data with wet lab physicochemical properties of crude laccase enzyme isolated from Rigidoporus sp. using wheat bran as solid substrate support towards dye decolorization. Molecular docking analysis of selected nine textile and non-textile dyes were performed using laccase from Rigidoporus lignosus as reference protein. Enzyme-based remediation methodology using crude enzyme enriched from solid state fermentation was applied to screen the effect of four influencing variables such as pH, temperature, dye concentration, and incubation time toward dye decolorization. The extracellular crude enzyme decolorized 69.8% Acid Blue 113, 45.07% Reactive Blue 19, 36.61% Reactive Orange 122, 30.55% Acid Red 88, 24.59% Direct Blue 14, 18.48% Reactive Black B, 16.49% Reactive Blue RGB, and 11.66% Acid Blue 9 at 100mg/l dye concentration at their optimal pH at room temperature under static and dark conditions after 1h of incubation without addition of any externally added mediators. Our wet lab studies approach, barring other factors, validate in silico for screening and ranking textile dyes based on their proximity to the T1 site. We are reporting for the first time a combinatorial approach involving in silico methods and wet lab-based crude laccase-mediated dye decolorization without any external mediators.

From Nanobiotechnology to Organic and Biological Monitoring of Health and Environment for Biosafety

This overview describes the optimal implementation and utilization of different, newly conceived nanosensors for human biosafety purposes, exploiting a variety of methods (amperometric, conductometric, spectrometric and nanogravimetric) and a wide range of nanocomposites, genes and recombinant enzymes. Namely, while biological nanosensors were designed based on Nucleic Acid Programmable Protein Arrays (NAPPA), with or without SNAP-tag, and on Langmuir-Blodgett (LB) thin films of recombinant laccase (Rigidoporus lignosus, formerly known as Rigidoporus microporus), organic nanosensors were based on matrices of calcium oxide (CaO) and on carbon nanotubes - either multi-walled (MWNTs) or single-walled (SWNTs) - embedded in poly(o-methylaniline) (POTO). Special attention was paid both to detecting useful and relevant substances (such as carbon dioxide, phenols and phenolic derivatives and compounds) and designing devices and molecules for human biosafety like vaccines and others, by means of amperometry, conductimetry, mass spectrometry (MS), and other label-free technologies such as quartz crystal microbalance with dissipation monitoring (QCM_D).

From Nanobiotechnology to Organic and Biological Monitoring of Health and Environment for Biosafety

This overview describes the optimal implementation and utilization of different, newly conceived nanosensors for human biosafety purposes, exploiting a variety of methods (amperometric, conductometric, spectrometric and nanogravimetric), and a wide range of nanocomposites, genes and recombinant enzymes. Namely, while biological nanosensors were designed based on Nucleic Acid Programmable Protein Arrays (NAPPA), with or without SNAPtag, and on Langmuir-Blodgett (LB) thin films of recombinant laccase (Rigidoporus lignosus, formerly known as Rigidoporus microporus), organic nanosensors were based on matrices of calcium oxide (CaO) and on carbon nanotubes–either multi-walled (MWNTs) or single-walled (SWNTs)– embedded in poly(o-methylaniline) (POTO). Special attention was paid both to detecting useful and relevant substances (such as carbon dioxide, phenols and phenolic derivatives and compounds) and designing devices and molecules for human biosafety like vaccines and others, by means of amperometry, conductimetry, mass spectrometry (MS) and other label-free technologies, such as quartz crystal microbalance with dissipation monitoring (QCM_D).

In silico study of structural determinants modulating the redox potential of Rigidoporus lignosus and other fungal laccases

Laccases are multicopper oxidases in which substrate oxidation takes place at the type-1 (T1) copper site. The redox potential (E 0) significantly varies amongst members of the family and is a key parameter for substrate specificity. Despite sharing highly conserved features at the T1 copper site, laccases span a large range of E 0, suggesting that the influence of the metal secondary coordination sphere is important. In silico analysis of structural determinants modulating the E 0 of Rigidoporus lignosus and other fungal laccases indicated that different factors can be considered. First, the length of the T1 copper coordinating histidine bond is observed to be longer in high E 0 laccases than in low E 0 ones. The hydrophobic environment around the T1 copper site appeared as another important structural determinant in modulating the E 0, with a stronger hydrophobic environment correlating with higher E 0. The analysis of hydrogen bonding network (HBN) around the T1-binding pocket revealed that the amino acids building up the metal binding site strongly interact with neighbouring residues and contribute to the stabilization of the protein folds. Changes in these HBNs that modified the Cu1 preferred coordination geometry lead to an increase of E 0. The presence of axial ligands modulates the E 0 of T1 to different extent. Stacking interactions between aromatic residues located in the second coordination shell and the metal ion coordination histidine imidazole ring have also been identified as a factor that modulates the E 0. The electrostatic interactions between the T1 copper site and backbone carbonyl oxygen indicate that Cu1–CO=NH distance is longer in the high E 0 laccases. In short, the in silico study reported herein identifies several structural factors that may influence the E 0 of the examined laccases. Some of these are dependent on the nature of the coordination ligands at the T1 site, but others can be ascribed to the hydrophobic effects, HBNs, axial ligations, stacking and electrostatic interactions, not necessary directly interacting with the copper metal.

Capability of selected mushrooms to biodegrade polyethylene

Many natural polymers are susceptible to microbial attack but synthetic polymers such as highmolecular weight polyethylene are generally difficult to degrade by microorganisms. Environmental concerns have led us to seek ways to resolve the problem that recalcitrant plastics pose on the ecology. The biodegradability of polyethylene films by selected exotic mushrooms was examined. In screening for the best polyethylene degrading-fungus, Pleurotus tuber-regium grew fastest on mineral salt medium containing polyethylene powder as sole carbon and energy followed by P. pulmonarius. Lentinus squarrosulus and Rigidoporus lignosus grew least on the medium. Degradation of polyethylene by P. tuber-regium and P. pulmonarius was determined by weight loss of sample and chemical changes measured by Fourier transform infra-red (FTIR) spectroscopy. Polyethylene biodegraded by P. tuber-regium and P. pulmonarius gave weight losses of 13.26% and 9.67% respectively. FTIR analysis showed additional absorbance at regions corresponding to carbonyl groups in the spectra of polyethylene biodegraded by P. tuber-regium and P. pulmonarius, suggesting that polyethylene was degraded oxidatively. The enzyme assays showed that Manganese peroxidase (MnP) may be the main enzyme involved in polyethylene degradation. These results suggest the capability of P. tuber-regium and P. pulmonarius to degrade polyethylene.

A surfactant tolerant laccase of Meripilus giganteus

A laccase (Lcc1) from the white-rot fungus Meripilus giganteus was purified with superior yields of 34% and 90% by conventional chromatography or by foam separation, respectively. Size exclusion chromatography (SEC) and sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) yielded a molecular mass of 55 kDa. The enzyme possessed an isoelectric point of 3.1 and was able to oxidize the common laccase substrate 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) at a pH of 2.0, whereas the enzyme was still able to oxidize ABTS and 2,6-dimethoxyphenol (DMP) at pH 6.0. Lcc1 exhibited low K ( m ) values of 8 μM (ABTS) and 80 μM (DMP) and remarkable catalytic efficiency towards the non-phenolic substrate ABTS of 37,437 k (cat)/k (m) (s(-1) mM(-1)). The laccase showed a high stability towards high concentrations of various metal ions, EDTA and surfactants indicating a considerable biotechnological potential. Furthermore, Lcc1 exhibited an increased activity as well as a striking boost of stability in the presence of surfactants. Degenerated primers were deduced from peptide fragments. The complete coding sequence of lcc1 was determined to 1,551 bp and confirmed via amplification of the 2,214 bp genomic sequence which included 12 introns. The deduced 516 amino acid (aa) sequence of the lcc1 gene shared 82% identity and 90% similarity with a laccase from Rigidoporus microporus. The sequence data may aid theoretical studies and enzyme engineering efforts to create laccases with an improved stability towards metal ions and bipolar compounds.

EVALUASI KOMBINASI ISOLAT TRICHODERMA MIKOPARASIT DALAM MENGENDALIKAN PENYAKIT AKAR PUTIH PADA BIBIT KARET

Evaluation of mycoparasitic Trichoderma isolate mixtures to control white root disease on rubber seedlings. Eight isolates of mycoparasitic Trichoderma, as single cultures or in isolate mixtures were tested for their biocontrol efficacy against rubber seedlings inoculated with one of three strains of Rigidoporus lignosus. Biocontrol efficacy of isolates was varied, but not significantly affected by strains of R. lignosus. Mixtures of four isolates were significantly (P < 0.05) reduced the disease severity and percentage of root necrotic as compared to mixtures of two isolates as well as single isolates. The highest disease suppression (65% relative to control) and reduction of inocula on rubber wood sticks (91% relative to control) was achieved in four isolate mixtures of Trichoderma virens (T1+T4+ T9+ T11).

UJI AKTIVITAS ANTIBIOSIS PSEUDOMONADS PENDARFLUOR TERHADAP Rigidoporus lignosus (Klotszch) Imazeki PENYEBAB PENYAKIT AKAR PUTIH

The potential of fluorescent bacteria as biological control agents for white root disease caused by Rigidoporus lignosus has been investigated. Isolation of bacteria from the soil using S1 media produced two fluorescent bacteria isolates. Using the Microbact 12A+12B method, both bacteria were identified as Pseudomonas fluorescens and P. aeruginosa. These two species of bacteria were then used as antibiosis activity test against R. lignosus. Four series antibiosis activity tests were done, that were antibiosis test of media culture bacteria growth to R. lignosus colony, antibiosis test of dry fluorescent pigment extract to R. lignosus, influence of Fe3+ to antibiosis activity of bacteria test, and affinity of media supernatant to Fe3+. The results were: antibiosis activity of King’s B (KB) media was more effective than media 523 in the inhibition of R. lignosus colony growth. There was no significant different antibiosis activity of dry fluorescent pigment extract from media KB and media 523 in the inhibition of R. lignosus colony growth. The level of Fe3+ in the media might influence antibiosis activity of fluorescent pigment. Affinity test of KB supernatant from fluorescent bacteria culture with Fe3+ showed an absorption peak of 410 nm on spectrophotometer, and none for the fungi. These results indicate that P. fluorescens and P. aeruginosa produce cathecol-type siderophore with high affinity against Fe3+ compared with hydroxamate-type siderophore which is generally produced by fungus.

Terpenoid constituents and antifungal activity of Aglaia forbesii seed against phytopathogens

Two new trisnortriterpenoids possessing a γ-lactone ring linked to the D-ring of a 3,4-secodammarane skeleton in a 20R configuration, named isoeichlerialactone (1) and methyl isoeichlerialactone (2), were isolated from the seed of Aglaia forbesii , along with the three dammarane triterpenes, isocabralealactone (3), isoeichlerianic acid (4), and aglinin A (5), the sesquiterpene spathulenol (6), and the widespread sterols β-sitosterol and stigmasterol. Their structures were established based on detailed spectroscopic analysis. Antifungal activity of A. forbesii seed against three phytopathogens, Phytophthora botryosa , P. palmivora , and Rigidoporus microporus , was carried out using the mycelium inhibition test and broth microdilution technique. Superior activity was exhibited by hexane and dichloromethane fractions containing the compounds 1, 4, and 5 as the main components. Subsequent antiphytopathogenic fungi tests proved that compounds 1, 4, and 5 possessed good antifungal activity.

Enhanced Laccase Production in White-Rot Fungus Rigidoporus lignosus by the Addition of Selected Phenolic and Aromatic Compounds

The white rot fungus Rigidoporus lignosus produces substantial amounts of extracellular laccase, a multicopper blue oxidase which is capable of oxidizing a wide range of organic substrates. Laccase production can be greatly enhanced in liquid cultures supplemented with various aromatic and phenolic compounds. The maximum enzyme activity was reached at the 21st or 24th day of fungal cultivation after the addition of inducers. The zymograms of extracellular fluid of culture preparation in the presence of inducers, at maximum activity day, revealed two bands with enzymatic activity, called Lac1 and Lac2, having different intensities. Lac2 band shows the higher intensity which changed with the different inducers. Laccase induction can be also obtained by adding to the culture medium olive mill wastewaters, which shows a high content of phenolic compounds.

Docking Simulation and Competitive Experiments Validate the Interaction Between the 2,5-Xylidine Inhibitor and Rigidoporus lignosus Laccase

Laccases are polyphenol oxidases which oxidize a broad range of reducing substrates, preferably phenolic compounds, and their use in biotechnological applications is increasing. Recently, the first X-ray structure of active laccase from white rot fungus Rigidoporus lignosus has been reported containing a full complement of copper ions. Comparison among selected fungal laccases of known 3D structure has shown that the Rigidoporus lignosus laccase has a very high similarity with the Trametes versicolor laccase that, being co-crystallized with 2,5-xylidine, shows a well defined binding pocket for the substrate. Global sequence alignment between Rigidoporus lignosus and Trametes versicolor laccases shows 73% of identity but, surprisingly, there is no identity and neither conservative substitutions between the residues composing the loops directly contacting the 2,5-xylidine. Moreover the structural alignment of these two enzymes identifies in these loops a striking structural similarity proposing the question if 2,5-xylidine may bind in same enzyme pocket. Here we report the protein-ligand docking simulation of 3D structure of Rigidoporus lignosus laccase and 2,5-xylidine. Docking simulation analyses show that spatial conformation of the two 2,5-xylidine binding pockets, despite differences in the residues directly contacting the ligand, may arrange a similar pocket that allows a comparable accommodation of the inhibitor. To validate these results the binding of 2,5-xylidine in the substrate cavity has been confirmed by kinetic competitive experiments.

THE CORELATIONS BETWEEN WHITE ROT (RIGIDOPORUS LIGNOSUS L.) INCIDENCE AND SOIL CHARACTERS OF RUBBER ECOSYSTEM IN PENUMANGAN BARU, LAMPUNG

The corelations between White Rot (Rigidoporus lignosus L.) incidence and soil characters of rubber ecosystem in Penumangan Baru, Lampung. A study was conducted to evaluate the corelation between soil characters and white rot incidence. The study was done in Penumangan Lampung from June 2007 to July 2008. Seven sites were observed on the incidence of white rot of indicator plants (cassava). Physical, chemical, and biological soil characters were correlated and regressed with white rot incidence. The results showed that there were correlation between white rot incidence and soil characters such as pH KCl, number of fungal genus (fungal diversity), Ca+, total cation, CEC, and saturation base. Ion Ca+, total cation, saturation base correlated positively with white rot incidence, on the contrary, fungal diversity, cation exchange capacity, and pH KCl correlated negatively with white rot incidence. Thus, efforts to increase fungal diversity, cation exchange capacity, and pH (in acidic soil) could be used as basic strategies to develope intergrated control of white rot disease.

Crystal Structure of a Two-domain Multicopper Oxidase

The two-domain multicopper oxidases are proposed to be key intermediates in the evolution of three-domain multicopper oxidases. A number of two-domain multicopper oxidases have been identified from genome sequences and are classified as type A, type B, or type C on the basis of the predicted location of the type 1 copper center. The crystal structure of blue copper oxidase, a type C two-domain multicopper oxidase from Nitrosomonas europaea, has been determined to 1.9 A resolution. Blue copper oxidase is a trimer, of which each subunit comprises two cupredoxin domains. Each subunit houses a type 1 copper site in domain 1 and a type 2/type 3 trinuclear copper cluster at the subunit-subunit interface. The coordination geometry at the trinuclear copper site is consistent with reduction of the copper ions. Although the overall architecture of blue copper oxidase is similar to nitrite reductases, detailed structural alignments show that the fold and domain orientation more closely resemble the three-domain multicopper oxidases. These observations have important implications for the evolution of nitrite reductases and multicopper oxidases.

Decolorisation of synthetic dyes by crude laccase from Rigidoporus lignosus W1

AbstractBACKGROUND: Effluents from the dyeing process containing dyes are difficult to degrade biologically. Therefore enzymatic dye decolorisation has received considerable attention recently. In this study the dye decolorisation potential of crude laccase from the white rot fungus Rigidoporus lignosus W1 was demonstrated on an anthraquinone dye, Remazol Brilliant Blue R (RBBR), and a triphenylmethane dye, malachite green (MG). Effects of pH, temperature and ionic strength on laccase activity and decolorisation efficiency were investigated.RESULTS: Native polyacrylamide gel electrophoresis (PAGE) and sodium dodecyl sulfate PAGE confirmed the decolorisation ability of the crude enzyme on RBBR and MG. A single laccase with a molecular mass of about 40 kDa appeared to be involved in the process. Efficient enzymatic decolorisation without redox mediator was achieved, with 39 mg L−1 MG being removed within 2 h and 160 mg L−1 RBBR within 1 h at 60 °C and pH 4.5. Although the laccase activity was inhibited in the presence of NaCl, it was renatured gradually in low concentrations of NaCl (<0.8 mol L−1), resulting in unusual dye decolorisation kinetics. Surprisingly, unusual storage stability at alkaline pH was observed, with the laccase activity being enhanced 1.5–2‐fold after 3 h of incubation.CONCLUSION: Crude laccase with unusual storage stability from the fungus R. lignosus W1 showed excellent decolorisation ability on RBBR and MG without redox mediator. This laccase would seem to be a good candidate for application in dye decolorisation and textile effluent biotreatment. Copyright © 2008 Society of Chemical Industry

Degradation of Polycyclic Aromatic Hydrocarbons by Rigidoporus lignosus and its Laccase in the Presence of Redox Mediators

The metabolism of polycyclic aromatic hydrocarbons (PAHs) was studied in vivo and in vitro in systems consisting of Rigidoporus lignosus and its laccase, in the presence of so-called "mediator" compounds. The static culture of the native fungal strain was able to metabolize anthracene and 2-methylanthracene, but not 9-nitroanthracene. The addition of redox mediators 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), 1-hydroxybenzotriazole (HBT) or violuric acid (VA) led to a significant increase in the degradation of substrates. The oxidation of PAHs was not significant when purified laccase was used without the addition of mediators. The addition of these compounds increased the oxidation of all substrates by approximately 70-80% after 72 h of incubation. The degradation rate was highest for 2-methylanthracene in the presence of VA.