Purification, kinetics and spectral characterisation of a new versatile peroxidase from a Bjerkandera sp. isolate

Screening for a more sustainable solution for decolorization of dyes and textile effluents using Candida and Yarrowia spp

Dyed effluents from textile industry are toxic and difficult to treat by conventional methods and biotechnological approaches are generally considered more environmentally friendly. In this work, yeast strains Candida parapsilosis, Yarrowia lipolytica and Candida pseudoglaebosa, isolated from wastewater treatment plants, were tested for their ability to decolorize textile dyes. Both commercial textile synthetic dyes (reactive, disperse, direct, acid and basic) and simulated textile effluents (a total of 32 solutions) were added to a Normal Decolorization Medium along with the yeast (single strains and consortia) and the decolorization was evaluated spectrophotometrically for 48-72 h. Yeasts were able to perform decolorization through adsorption and biodegradation for 28 of the dyes and simulated effluents by more than 50%. Y. lipolytica and C. pseudoglaebosa presented the best results with a true decolorization of reactive dyes, above 90% at 100 mg l^-1, and simulated effluents at 5 g l^-1 of concentration. Enzyme production was evaluated: oxidoreductase was found in the three yeasts, whereas tyrosinase was only found in Y. lipolytica and C. pseudoglaebosa. Y. lipolytica and C. pseudoglaebosa are a potential biotechnological tool for dye degradation in textile wastewaters, especially those containing reactive dyes and a promising tool to integrate in bioremediation solutions, contributing to circular economy and eco sustainability in the water sector since the treated water could possibly be reused for irrigation.

Decolorization and biodegradation of melanoidin contained in beet molasses by an anamorphic strain of Bjerkandera adusta CCBAS930 and its mutants

We used a ligninolytic strain of the white-rot fungus B. adusta CCBAS 930 and its mutants with modified ligninolytic activity to assess their potential to remove of molasses. The analyzed strains have been shown to be able to decolorize 1% or 2% molasses solutions containing brown-colored toxic melanoidins. It was found that the decolorization process was determined by the transition to the stage of production of sporulating aerial mycelium (liquid and agar cultures) coupled with an increase in peroxidase activity, which was accompanied by a decrease in the level of melanoidin, free radicals, and phenolic compounds. Four different peroxidase activities were detected in post-culture liquids, i.e. horseradish-like (HRP-like), manganese-dependent (MnP), lignin (LiP), and versatile (VP) peroxidase activities. The HRP-like peroxidase was characterized by the highest activity. The efficiency of removal of melanoidins from a 1% molasses solution by the parental strain and the mutants was dependent on the culture method. The highest efficiency was noted in immobilized cultures (threefold higher than in the mycelium-free cultures), which was accompanied by stimulation of HRP-like peroxidase activity. Mutant 930-5 was found to be the most effective in the decolorization and decomposition of melanoidin. The HRP-like activity in the immobilized cultures of B. adusta 930-5 was 640-fold higher than in the mycelium-free cultures of the fungus. Moreover, decolorization and biodegradation of melanoidin by B. adusta CCBAS 930 and 930-5 was coupled with detoxification.

Addition of new catalytic sites on the surface of versatile peroxidase for enhancement of LRET catalysis

Versatile peroxidase (VP) from Bjerkandera adusta is an enzyme able to oxidize bulky and high-redox substrates trough a Long-Range Electron Transfer (LRET) pathway. In this study, the introduction of radical-forming aromatic amino acids by chemical modification of the protein surface was performed, and the catalytic implications of these additional surface active-sites on the oxidation of 2,6-dimethylphenol, Mn²⁺ and Remazol Brilliant Blue R (RBBR) were determined. These three different substrates are oxidized in different active-sites of enzyme molecule, of which the high redox RBBR the only one that is transformed by an external radical formed on the protein surface. Both catalytic constants k_cat and K_M were significantly affected by the chemical modifications. Tryptophan- and tyrosine-modified VP showed higher catalytic transformation than the unmodified enzyme for RBBR, while the Mn²⁺ oxidation was significantly reduced by all chemical modifications. Electron Paramagnetic Resonance studies demonstrated the formation of additional protein-based radicals after the chemical modification with radical-forming amino acids. In addition, the catalytic rate of the LRET-mediated transformation showed a good correlation with the ionization energy of the additional amino acid on the protein surface.

Biodegradation of asphaltene and petroleum compounds by a highly potent Daedaleopsis sp

Petroleum, as the major energy source, is indispensable from our lives. Presence of compounds resistant to degradation can pose risks for human health and environment. Basidiomycetes have been considered as powerful candidates in biodegradation of petroleum compounds via secreting ligninolytic enzymes. In this study a wood-decaying fungus was isolated by significant degradation ability that was identified as Daedaleopsis sp. by morphological and molecular identification methods. According to GC/MS studies, incubation of heavy crude oil with Daedaleopsis sp. resulted in increased amounts of <C24 hydrocarbons and decreased amounts of >C24 compounds. Degradation of asphaltene, anthracene, and dibenzofuran by the identified fungal strain was determined to evaluate its potential in biodegradation. After 14 days of incubation, Daedaleopsis sp. could degrade 93.7% and 91.2% of anthracene and dibenzofuran, respectively, in pH 5 and 40 °C in optimized medium, as revealed by GC/FID. Notably, analysis of saturates, aromatics, resins, and asphaltenes showed a reduction of 88.7% and 38% in asphaletene and aromatic fractions. Laccase, lignin peroxidase, and manganese peroxidase activities were enhanced from 51.3, 145.2, 214.5 U ml^-1 in the absence to 121.5, 231.4, and 352.5 U ml^-1 in the presence of heavy crude oil, respectively. This is the first report that Daedaleopsis sp. can degrade asphaltene and dibenzofuran. Moreover, compared to the reported results of asphaltene biodegradation, this strain was the most successful. Thus, Daedaleopsis sp. could be a promising candidate for biotransformation of heavy crude oil and biodegradation of recalcitrant toxic compounds.

Biodegradation of polycyclic aromatic hydrocarbons (PAHs) by fungal enzymes: A review

Polycyclic aromatic hydrocarbons (PAHs) are a large group of chemicals. They represent an important concern due to their widespread distribution in the environment, their resistance to biodegradation, their potential to bioaccumulate and their harmful effects. Several pilot treatments have been implemented to prevent economic consequences and deterioration of soil and water quality. As a promising option, fungal enzymes are regarded as a powerful choice for degradation of PAHs. Phanerochaete chrysosporium, Pleurotus ostreatus and Bjerkandera adusta are most commonly used for the degradation of such compounds due to their production of ligninolytic enzymes such as lignin peroxidase, manganese peroxidase and laccase. The rate of biodegradation depends on many culture conditions, such as temperature, oxygen, accessibility of nutrients and agitated or shallow culture. Moreover, the addition of biosurfactants can strongly modify the enzyme activity. The removal of PAHs is dependent on the ionization potential. The study of the kinetics is not completely comprehended, and it becomes more challenging when fungi are applied for bioremediation. Degradation studies in soil are much more complicated than liquid cultures because of the heterogeneity of soil, thus, many factors should be considered when studying soil bioremediation, such as desorption and bioavailability of PAHs. Different degradation pathways can be suggested. The peroxidases are heme-containing enzymes having common catalytic cycles. One molecule of hydrogen peroxide oxidizes the resting enzyme withdrawing two electrons. Subsequently, the peroxidase is reduced back in two steps of one electron oxidation. Laccases are copper-containing oxidases. They reduce molecular oxygen to water and oxidize phenolic compounds.

Production of versatile peroxidase from Pleurotus eryngii by solid-state fermentation using agricultural residues and evaluation of its catalytic properties

Interest in production of ligninolytic enzymes has been growing over recent years for their use in various applications such as recalcitrant pollutants bioremediation; specifically, versatile peroxidase (VP) presents a great potential due to its catalytic versatility. The proper selection of the fermentation mode and the culture medium should be an imperative to ensure a successful production by an economic and available medium that favors the process viability. VP was produced by solid-state fermentation (SSF) of Pleurotus eryngii, using the agricultural residue banana peel as growth medium; an enzymatic activity of 10,800 U L(-1) (36 U g(-1) of substrate) was detected after 18 days, whereas only 1800 U L(-1) was reached by conventional submerged fermentation (SF) with glucose-based medium. The kinetic parameters were determined by evaluating the H2O2 and Mn(2+) concentration effects on the Mn(3+)-tartrate complex formation. The results indicated that although the H2O2 inhibitory effect was observed for the enzyme produced by both media, the reaction rates for VP obtained by SSF were less impacted. This outcome suggests the presence of substances released from banana peel during the fermentation, which might exhibit a protective effect resulting in an improved kinetic behavior of the enzyme.

EPR and LC-MS studies on the mechanism of industrial dye decolorization by versatile peroxidase from Bjerkandera adusta

The mechanisms of industrial dye transformation by versatile peroxidase were elucidated. Purified versatile peroxidase from Bjerkandera adusta was able to decolorize different classes of dyes including azo and phthalocyanines, but unable to transform any of the anthraquinones tested. Kinetic constants for selected dyes were determined and the transformation products were analyzed by EPR spectroscopy and mass spectrometry. The EPR and MS analyses of the enzymatic decolorization products showed the cleavage of the azo bond in azo dyes and the total disruption of the phthalocyaninic ring in phthalocyanine dyes. The EPR analysis on two copper-containing dyes, reactive violet 5 (azo) and reactive blue 72 (phthalocyanine), showed that the transformation can or not break the metal-ion coordination bond according the dye nature. The role of the catalytic Trp172 in the dye transformation by a long-range electron transfer pathway was confirmed and the oxidation mechanisms are proposed and discussed.

Anthraquinone dyes decolorization capacity of anamorphic Bjerkandera adusta CCBAS 930 strain and its HRP-like negative mutants

Cultures of the anamorphic fungus Bjerkandera adusta CCBAS 930 decolorizing, in stationary cultures, 0.01 % solutions of carminic acid and Poly R-478, were characterised by a strong increase in the activity of the horseradish peroxidase (HRP-like) and manganese-dependent peroxidase (MnP) at a low activity of lignin peroxidase. Genotypically modified mutants of B. adusta CCBAS 930: 930-5 and 930-14, with total or partial loss of decolorization capabilities relative to anthraquinonic dyes, showed inhibition of the activity of HRP-like peroxidase and MnP. Whereas, compared to the parental strain, in the mutant cultures there was an increase in the activity of lignin peroxidase and laccase. The paper presents a discussion of the role of the studied enzymatic activities in the process of decolorization of anthraquinonic dyes by the strain B. adusta CCBAS 930.

Biotechnological procedures to select white rot fungi for the degradation of PAHs

White rot fungi are essential in forest ecology and are deeply involved in wood decomposition and the biodegradation of various xenobiotics. The fungal ligninolytic enzymes involved in these processes have recently become the focus of much attention for their possible biotechnological applications. Successful bioremediation requires the selection of species with desirable characteristics. In this study, 150 taxonomically and physiologically diverse white rot fungi, including 55 species, were investigated for their performance in a variety of biotechnological procedures, such as dye decolorization, gallic acid reaction, ligninolytic enzymes, and tolerance to four PAHs, phenanthrene, anthracene, fluoranthene, and pyrene. Among these fungi, six isolates showed the highest (>90%) tolerance to both individual PAH and mixed PAHs. And six isolates oxidized gallic acid with dark brown color and they rapidly decolorized RBBR within ten days. These fungi revealed various profiles when evaluated for their biotechnological performance to compare the capability of degradation of PAHs between two groups selected. As the results demonstrated the six best species selected from gallic acid more greatly degraded four PAHs than the other isolates selected via tolerance test. It provided that gallic acid reaction test can be performed to rank the fungi by their ability to degrade the PAHs. Most of all, Peniophora incarnata KUC8836 and Phlebia brevispora KUC9033 significantly degraded the four PAHs and can be considered prime candidates for the degradation of xenobiotic compounds in environmental settings.

Decolorization of Remazol Brilliant Blue (RBBR) and Poly R-478 dyes by Bjerkandera adusta CCBAS 930

An anamorphic Bjerkandera adusta CCBAS 930 strain isolated from soil was found to decolorize two anthraquinonic dyes: Remazol Brilliant Blue R and Poly R-478. The reduction in the level of phenolic compounds in liquid B. adusta cultures containing RBBR and Poly R-478 was correlated with decolorization of studied dyes, which suggested their biodegradation. It was shown that this process was coupled with induction of secondary metabolism (idiophase) and peak peroxidase activity in culture medium, and the appearance of aerial mycelium. Decolorization of dyes depended on the presence of glucose (cometabolism).

Kinetic and thermodynamic characterization of the functional properties of a hybrid versatile peroxidase using isothermal titration calorimetry: Insight into manganese peroxidase activation and lignin peroxidase inhibition

Isothermal titration calorimetry (ITC) was developed for measuring lignin peroxidase (LiP) and manganese peroxidase (MnP) activities of versatile peroxidase (VP) from Bjerkandera adusta. Developing an ITC approach provided an alternative to colorimetric methods that enabled reaction kinetics to be accurately determined. Although VP from Bjerkandera adjusta is a hybrid enzyme, specific conditions of [Mn+2] and pH were defined that limited activity to either LiP or MnP activities, or enabled both to be active simultaneously. MnP activity was found to be more efficient than LiP activity, with activity increasing with increasing concentrations of Mn+2. These properties of MnP were explained by a second metal binding site involved in homotropic substrate (Mn+2) activation. The activation of MnP was also accompanied by a decrease in both activation energy and substrate (Mn) affinity, reflecting a flexible enzyme structure. In contrast to MnP activity, LiP activity was inhibited by high dye (substrate) concentrations arising from uncompetitive substrate inhibition caused by substrate binding to a site distinct from the catalytic site. Our study provides a new level of understanding about the mechanism of substrate regulation of catalysis in VP from B. adjusta, providing insight into a class of enzyme, hybrid class II peroxidases, for which little experimental data is available.

Bioligninolysis: recent updates for biotechnological solution

Bioligninolysis involves living organisms and/or their products in degradation of lignin, which is highly resistant, plant-originated polymer having three-dimensional network of dimethoxylated (syringyl), monomethoxylated (guaiacyl), and non-methoxylated (p-hydroxyphenyl) phenylpropanoid and acetylated units. As a major repository of aromatic chemical structures on earth, lignin bears paramount significance for its removal owing to potential application of bioligninolytic systems in industrial production. Early reports illustrating the discovery and cloning of ligninolytic biocatalysts in fungi was truly a landmark in the field of enzymatic delignification. However, the enzymology for bacterial delignification is hitherto poorly understood. Moreover, the lignin-degrading bacterial genes are still unknown and need further exploration. This review deals with the current knowledge about ligninolytic enzyme families produced by fungi and bacteria, their mechanisms of action, and genetic regulation and reservations, which render them attractive candidates in biotechnological applications.

Expression of soluble versatile peroxidase of Bjerkandera adusta in Escherichia coli

Versatile peroxidase from white rot fungus Bjerkandera adusta was over-expressed in a soluble form in Escherichia coli. In the constructed enzyme model based on the selected gene from B. adusta, the active sites for oxidation of Mn(2+) ions and for oxidation of aromatic substrates were identified, both characteristic for versatile peroxidase. For over-expression of the recombinant enzyme different host strains, media formulations, growth temperatures, and fusion partners were tested. With the bacterial strain BL21(DE3)pLysS cultivated at 25 degrees C in auto-induction medium and presence of heme, a soluble peroxidase with incorporated heme and activity against different substrates was obtained. By exploiting an appropriate expression system and providing suitable culture conditions, the recombinant fungal peroxidases in soluble form can be produced in bacteria.

Purification, characterization, and gene cloning of Ceriporiopsis sp. strain MD-1 peroxidases that decolorize human hair melanin

Ceriporiopsis sp. strain MD-1, isolated from forest soil, produced several extracellular enzymes that decolorized human hair melanin. Among them, three enzymes (E1, E2-1, and E2-2) were purified to homogeneity and characterized. The enzymes required hydrogen peroxide in their enzyme reactions and, typical of other fungal peroxidases, oxidized various phenol compounds such as guaiacol, but not 3,4-dimethoxybenzyl alcohol. The spectra of the three enzymes showed an absorption maximum at 406 nm, indicating that they were heme proteins. However, the A(406)/A(280) values of the enzymes were below 0.4, which was lower than those of other peroxidases. E2-1 and E2-2 were similar to each other in their molecular and catalytic properties, and they possibly represent products of posttranslational modifications and/or allelic variants of the same gene, mdcA. The corresponding cDNA was cloned and sequenced; the deduced amino acid sequence showed high identities to the manganese peroxidases from other microorganisms. The specific activities and K(m) values of E2-1 and E2-2 for synthetic and human hair melanins were much higher than those of Phanerochaete chrysosporium manganese peroxidase and lignin peroxidase.