White-rot Fungal Cultures Research Articles

Decolorization of azo dyes by Phanerochaete chrysosporium and Pleurotus sajorcaju

Many synthetic dyes present in industrial wastewaters are resistant to degradation by conventional treatments. Decolorization of four synthetic azo dyes was examined in two white rot fungal cultures. In solidified culture medium, Phanerochaete chrysosporium partially decolorized all the dyes tested, while Pleurotus sajorcaju totally decolorized amaranth, new coccine, and orange G, but not tartrazine. In liquid culture medium, P. chrysosporium totally decolorized amaranth, new coccine and orange G, and 60% tartrazine. Pleurotus sajorcaju totally decolorized amaranth and new coccine, 50% orange G and a maximum of 20% tartrazine. Neither fungus showed lignin peroxidase or veratryl alcohol oxidase activities, suggesting that these enzymes may not be involved in the decolorization. Manganese-peroxidase and β-glucosidase may be involved in the decolorization of the dyes by P. chrysosporium, whereas in P. sajorcaju a laccase active toward o-dianisidine, and glucose-1-oxidase might participate in the process.

Consecutive polymerization and depolymerization of kraft lignin by trametes cingulata

In extracellular solutions from white-rot fungal cultures, lignin components typically encounter opposing tendencies to be polymerized and depolymerized. The enzymes most commonly purported to bring about lignin depolymerization—lignin peroxidase, manganese-dependent peroxidase and laccase—can all act as single-electron oxidants. Accordingly they may produce from particular lignin monomer residues, either indirectly or directly, phenoxy radicals that will undergo bimolecular coupling, unless they are otherwise pre-emptively transformed. The present work has sought to elucidate whether discrimination between polymerization and depolymerization is really so precariously established in the progenitorial step of the biodegradative pathway. Some white-rot fungi express no detectable peroxidase activity of any kind and yet degrade lignins very effectively. For the sake of simplicity, one of these, Trametes cingulata, was selected to explore whether there might be some connection between lignin polymerization and depolymerization in vivo. The (Mn-free) culture medium was a multicomponent homogeneous solution containing 0.55 gl −1 softwood kraft lignin, which was adopted as the substrate because of its adequate solubility. As it grew vegetatively, T. cingulata polymerized the dissolved lignin components but then, after cessation of primary growth, the high molecular weight polymerized substrate was completely degraded. No lignin peroxidase or Mn-dependent peroxidase activity was detected in the extracellular culture solution during either metabolic phase, although (laccase-like) oxidase activity towards 2,2′-azinobis(3-ethylbenzthiazoline-6-sulfonate) (ABTS) persisted throughout the entire process. The results suggest that the overall effect of T. cingulata upon the kraft lignin substrate is governed by the consecutive release of distinct polymerizing and depolymerizing enzymes.

Decolorization and biodegradation of anaerobically digested sugarcane molasses spent wash effluent from biomethanation plants by white-rot fungi

Four white-rot fungal cultures were examined for their ability to decolorize and bioremediate anaerobically digested molasses spent wash (DMSW) generated by biomethanation plants. Two cultures Coriolus versicolor and Phanerochaete chrysosporium showed an ability to decolorize and reduce the chemical oxygen demand (COD) of diluted DMSW (12·5% v/v). Both cultures required an additional labile carbon source to carry out decolorization while additional organic nitrogen did not significantly improve it further. Optimum growth and decolorization occurred at 35–40°C, pH 5·0, glucose at 3–5%(w/v). Maximum decolorization (71·5 and 53·5%) and COD reduction (90·0 and 73·0%) were achieved in 6·25% (v/v) DMSW medium by C. versicolor and P. chrysosporium, respectively. These values decreased significantly at higher concentrations of DMSW (12·5 and 25% v/v), nevertheless both cultures have profound potential applications in reducing the pollution of DMSW effluent prior to its disposal.

Stabilization of lignin peroxidases in white rot fungi by tryptophan.

Supplementation of various cultures of white rot fungi with tryptophan was found to have a large stimulatory effect on lignin peroxidase activity levels. This enhancement was greater than that observed in the presence of the lignin peroxidase recycling agent veratryl alcohol. Using reverse transcription-PCR, we found that tryptophan does not act to induce lignin peroxidase expression at the level of gene transcription. Instead, the activity enhancement observed is likely to result from the protective effect of tryptophan against H2O2 inactivation. In experiments using a partially purified lignin peroxidase preparation, tryptophan and its derivative indole were determined to function in the same way as veratryl alcohol in converting compound II, an oxidized form of lignin peroxidase, to ferric enzyme, thereby completing the catalytic cycle. Furthermore, tryptophan was found to be a better substrate for lignin peroxidase than veratryl alcohol. Inclusion of either tryptophan or indole enhanced the oxidation of the azo dyes methyl orange and Eriochrome blue black. Stimulation of azo dye oxidations by veratryl alcohol has previously been shown to be due to its enzyme recycling function. Our data allow us to propose that tryptophan stabilizes lignin peroxidase by acting as a reductant for the enzyme.

Ligninase-catalysed decolorization of synthetic dyes

Many synthetic dyes in industrial wastewaters are resistant to degradation in conventional biological treatment process. Decolorization of eight synthetic dyes including azo, anthraquinone, metal complex and indigo were examined in white-rot fungal cultures and by fungal peroxidase-catalysed oxidation. The dyes were not decolorized by manganese-dependent peroxidase (MnP) while above 80% color was removed by ligninase-catalysed oxidation. Dye decolorization rate increased linearly with ligninase doses. Compared with fungal cultures in which ligninase was detected, partially purified ligninase showed a consistent and higher extent of dye decolorization with other essential components being provided such as veratryl alcohol, hydrogen peroxide and acidic pH (3.5–5). Veratryl alcohol had a critical concentration level above which no further effect on dye decolorization was observed. Depending on the influence of H 2O 2 on dye decolorization, the eight dyes can be divided into two groups; one had an optimum H 2O 2 concentration and the other showed increased decolorization with high H 2O 2 doses. Dye concentration had a negative effect on decolorization rate in general. The dye concentration above which the negative effect was observed varied from 10 to 125 mg/L, depending on individual dye structure. These results indicate that a highly efficient bioprocess using white-rot fungi to remove color from industrial effluents should produce ligninase, H 2O 2, veratryl alcohol continuously and coordinately under acidic condition and controlled back-mixing flow of wastewater.

Metabolic pathways utilized by Phanerochaete chrysosporium for degradation of the cyclodiene pesticide endosulfan

Recent studies have shown that cultures of white rot fungi not favoring the production of lignin and manganese peroxidases are effective in degrading certain xenobiotics. In this study we have used endosulfan as a model xenobiotic to assess the enzymatic mechanisms of pesticide metabolism under ligninolytic (nutrient-deficient) and nonligninolytic (nutrient-rich) culture conditions. Rapid metabolism of this chlorinated pesticide occurred under each nutrient condition tested. However, the extent of degradation and the nature of the metabolic products differed for nutrient-deficient and nutrient-rich media. The pathways for endosulfan metabolism were characterized by analysis of the fungal metabolites produced. The major endosulfan metabolites were identified by gas chromatography-electron capture detection and gas chromatography-mass spectrometry as endosulfan sulfate, endosulfan diol, endosulfan hydroxyether, and a unknown metabolite tentatively identified as endosulfan dialdehyde. The nature of the metabolites formed indicates that this organism utilizes both oxidative and hydrolytic pathways for metabolism of this pesticide. Piperonyl butoxide, a known cytochrome P-450 inhibitor, significantly inhibited the oxidation of endosulfan to endosulfan sulfate and enhanced hydrolysis of endosulfan to endosulfan diol. We suggest that the metabolism of endosulfan is mediated by two divergent pathways, one hydrolytic and the other oxidative. Judging by the inactivity of extracellular fluid and partially purified lignin peroxidase in metabolizing endosulfan, we conclude that metabolism of this compound does not involve the action of extracellular peroxidases.

Determination of Manganese Peroxidase Activity with 3-Methyl-2-benzothiazolinone Hydrazone and 3-(Dimethylamino)benzoic Acid

This method was proposed earlier for measuring glucose in a peroxidase-glucose oxidase system but has not been studied for determination of manganese peroxidase (MnP) activity. The assay is based on the oxidative coupling of 3-methyl-2-benzothiazolinone hydrazone (MBTH) and 3-(dimethylamino)benzoic acid (DMAB). The reaction of MBTH and DMAB in the presence of H2O2, Mn2+, and MnP gives a deep purple-blue color with a broad absorption band with a peak at 590 nm. The extinction coefficient is high (53,000 M−1 cm−1), so low MnP activities can be detected. Lignin peroxidase and laccase, usually present in cultures of white rot fungi, gave little or no interference at the concentrations tested. However, slight interference from very high LiP activity may occur at very low MnP activity.

Ligninolytic enzymes of the fungus Panus tigrinus[formula omitted]: Biosynthesis, purification and properties

Extracellular Mn-dependent peroxidase and oxidase have been purified from the culture of white rot fungus P. tigrinus 8 18 grown on wheat straw. Some physico-chemical and ligninolytic properties of these enzymes have been investigated. Both enzymes have been shown to decompose a dimeric model compound of β-β′ type (and oxidase, also to demethoxylate substrate); to cleave C α-C β in a nonphenolic model compound of β-1 type (Mn-peroxidase, also to split the C β-C 4 bond); to be involved in lignin polymerization-depolymerization reactions. Based on the data presented and considering the absence of lignin peroxidase in the extracellular ligninolytic enzyme complex of P. tigrinus, Mn-peroxidase is suggested to be the key enzyme of the complex.

Some factors affecting bioconversion of whole bagasse into fungal biomass

AbstractTwo isolated basidiomycetes mould cultures Polyporus BH1 and Polyporus BW1 and two standard white rot fungal cultures Pleurotus ostreatus and Polyporus versicolor were cultivated under submerged conditions on whole (untreated) bagasse for protein production. Some factors promoting better bioconversion were studied and selected. NORKRAN's medium at pH 5.0 with 1.0% bagasse of 80 mesh particle size using an appropriate quantity of inoculum, supplementing medium with an amino acid, without addition of any vitamin, etc. gave best results.

Bioconversion of sugarcane bagasse with white rot fungi

Four cultures of white rot fungi were screened for their ability to degrade lignin and carbohydrates of sugarcane bagasse and their effect on changes ininvitro digestibility.Polyporushirsutus534 degraded maximum lignin and carbohydrates accompanied with the highest increase in digestibility, but increase in nutrient availability was maximum withPleurotussajorcaju (Z-6) due to lower dry matter loss during the process of fungal treatment. All the fungi tested exceptPolyporuscaperatus Berk. degraded lignin more selectively than the other components of sugarcane bagasse.

Bioconversion of organosoluble lignins by different types of fungi

Technical organosoluble lignins could serve as growth substrate for several fungi of different ecotypes. Certain species of fungi increased the water solubility of the lignin, depending on the glucose concentration in the medium. The solubilization rate was increased also by successive growth of fungi on the lignin. All types of organosoluble lignin induced high activities of extracellular phenoloxidase (E.C.1.14.18.1) in cultures of white-rot fungi. The enzyme activities obtained on organosoluble lignins were higher than on lignosulfonates. Due to the action of phenoloxidases two water-soluble, acid-precipitable lignin polymerizates with different physical properties were formed. The nitrogen and glucose content in the medium plays an important role in the polymerization.