Comparison of physico-chemical characteristics of four laccases from different basidiomycetes

Role and structure of the small subunit forming heterodimers with laccase-like enzymes

Unlike laccases sensu stricto, which are usually monomeric enzymes, laccase-like enzymes recently re-classified as Novel Laccases (NLACs) are characterized by the formation of heterodimers with small proteins (subunits) of unknown function. Here the NLAC from Pleurotus eryngii (PeNL) and a small protein selected from the fungal genome, that is homologous to reported POXA3 from Pleurotus ostreatus, were produced in Aspergillus oryzae separately or together. The two proteins interacted regardless of whether the small subunit was co-expressed or exogenously added to the enzyme. The stability and catalytic activity of PeNL was significantly enhanced in the presence of the small subunit. Size exclusion chromatography-multi angle light scattering (SEC-MALS) analysis confirmed that the complex PeNL-ss is a heterodimer of 77.4 kDa. The crystallographic structure of the small protein expressed in Escherichia coli was solved at 1.6 Å resolution. This is the first structure elucidated of a small subunit of a NLAC. The helix bundle structure of the small subunit accommodates well with the enzyme model structure, including interactions with specific regions of NLACs and some amino acid residues of the substrate-binding loops.

Laccase Engineering: Redox Potential Is Not the Only Activity-Determining Feature in the Metalloproteins

Laccase, one of the metalloproteins, belongs to the multicopper oxidase family. It oxidizes a wide range of substrates and generates water as a sole by-product. The engineering of laccase is important to broaden their industrial and environmental applications. The general assumption is that the low redox potential of laccases is the principal obstacle, as evidenced by their low activity towards certain substrates. Therefore, the primary goal of engineering laccases is to improve their oxidation capability, thereby increasing their redox potential. Even though some of the determinants of laccase are known, it is still not entirely clear how to enhance its redox potential. However, the laccase active site has additional characteristics that regulate the enzymes' activity and specificity. These include the electrostatic and hydrophobic environment of the substrate binding pocket, the steric effect at the substrate binding site, and the orientation of the binding substrate with respect to the T1 site of the laccase. In this review, these features of the substrate binding site will be discussed to highlight their importance as a target for future laccase engineering.

Peculiar Properties of Template-Assisted Aniline Polymerization in a Buffer Solution Using Laccase and a Laccase-Mediator System as Compared with Chemical Polymerization

The conventional chemical polymerization of aniline has been described in multiple publications, while enzymatic polymerization has been poorly explored. A comparative study of the template-assisted enzymatic and chemical polymerization of aniline in a buffer solution of sodium dodecylbenzenesulfonate micelles was performed for the first time. The high-redox potential laccase from the fungus Trametes hirsuta was used as a catalyst and air oxygen served as an oxidant. Potentiometric and spectral methods have shown that oligomeric/polymeric products of the enzymatic polymerization of aniline are synthesized in the conducting emeraldine salt form immediately after the reaction is initiated by the enzyme. The use of the laccase-mediator system enabled a higher rate of enzymatic polymerization and a higher yield of final products. Potassium octocyanomolybdate (IV) served as a redox mediator. The products of the enzymatic polymerization of aniline were studied by the ATR-FTIR, MALDI-TOF and atomic force microscopy methods. The chemical oxidative polymerization of aniline under the same conditions resulted in forming a non-conducting dark brown product.

The potential of fungi in the bioremediation of pharmaceutically active compounds: a comprehensive review

The ability of fungal species to produce a wide range of enzymes and metabolites, which act synergistically, makes them valuable tools in bioremediation, especially in the removal of pharmaceutically active compounds (PhACs) from contaminated environments. PhACs are compounds that have been specifically designed to treat or alter animal physiological conditions and they include antibiotics, analgesics, hormones, and steroids. Their detrimental effects on all life forms have become a source of public outcry due their persistent nature and their uncontrolled discharge into various wastewater effluents, hospital effluents, and surface waters. Studies have however shown that fungi have the necessary metabolic machinery to degrade PhACs in complex environments, such as soil and water, in addition they can be utilized in bioreactor systems to remove PhACs. In this regard, this review highlights fungal species with immense potential in the biodegradation of PhACs, their enzymatic arsenal as well as the probable mechanism of biodegradation. The challenges encumbering the real-time application of this promising bioremediative approach are also highlighted, as well as the areas of improvement and future perspective. In all, this paper points researchers to the fact that fungal bioremediation is a promising strategy for addressing the growing issue of pharmaceutical contamination in the environment and can help to mitigate the negative impacts on ecosystems and human health.

Laccase-mediated formation of hydrogels based on silk-elastin-like protein polymers with ultra-high molecular weight

As artificial extracellular matrix-like materials, silk-elastin-like protein (SELP) hydrogels, with excellent mechanical properties, high tunability, favorable biocompatibility, and controlled degradability, have become an important candidate in biomedical materials. In this study, SELP is composed of silk-like (GAGAGS) and elastin-like (GXGVP) tandem repeats, in which X residues are set as tyrosine and lysine. Furthermore, SELP polymers are prepared via SpyTag/SpyCatcher. To explore a gentler and more efficient enzymatic crosslinking method, an innovative method was invented to apply laccase to catalyze the formation of SELP hydrogels. Gelation could be successfully achieved in 2-5 min . SELP hydrogels mediated by laccase had the characteristic of low swelling rate, which could maintain a relatively stable shape even when immersed in water, and hence had the potential to be further developed into injectable biomaterials. Additionally, SELP hydrogels cross-linked by laccase showed excellent biocompatibility verified by L929 and HEK 293 T cells with cell viability >93.8 %. SELP hydrogels also exhibit good properties in sustained drug release and cell encapsulation in vitro. This study demonstrates a novel method to construct SELP hydrogels with excellent biocompatibility and expands the possibility of SELP-based material applications in biomedical fields.

Laccase mediated delignification of wasted and non-food agricultural biomass: Recent developments and challenges

Utilization of microbial laccases is considered as the cleaner and target specific biocatalytic mechanism for the recovery of cellulose and hemicelluloses from nonfood and wasted agricultural, lignocellulosic biomass (LCB). The extent of lignin removal by laccase depends on the biochemical composition of biomass and the redox potential (E⁰) of the biocatalyst. Intensive research efforts are going on all over the world for the recognition of appropriate and easily available agricultural lignocellulosic feedstocks to exploit maximally for the production of value-added bioproducts and biofuels. In such circumstances, laccase can play a major role as a leading biocatalyst and potent substitute for chemical based deconstruction of the lignocellulosic materials. The limited commercialization of laccase at an industrial scale has been feasible due to its full working efficiency mostly expressed in the presence of cost intensive redox mediators only. Although, recently there are some reports that came on the mediator free biocatalysis of enzyme but still not considerably explored and neither understood in depth. The present review will address the various research gaps and shortcomings that acted as the big hurdles before the complete exploitation of laccases at an industrial scale. Further, this article also reveals insights on different microbial laccases and their diverse functional environmental conditions that affect the deconstruction process of LCB.

Production of a novel laccase from Ceratorhiza hydrophila and assessing its potential in natural dye fixation and cytotoxicity against tumor cells

BACKGROUND

Flavonoid natural dyes have gained attention because they are nontoxic and eco-friendly. However, they do not work effectively with artificial fibers and require the use of mordants, which are considered as hazardous chemicals. Laccase enzyme catalyzes the oxidation of phenols, forming phenoxyl radicals that undergo a further polymerization process. So, laccase can oxidize flavonoid dyes, and it can be used instead of harmful mordants in flavonoid dye fixation on cotton fabrics. Laccases also are involved in a variety of metabolic processes, and they have anti-proliferative effects toward HepG2 and MCF-7 tumor cells.

RESULTS

Among fifteen fungal isolates, the fungus Ceratorhiza hydrophila isolated from the submerged plant Myriophyllum spicatum was selected as the most potent laccase producer. Optimization of the production medium resulted in a 9.9-fold increase in laccase productivity. The partially purified Ceratorhiza hydrophila laccase could successfully improve the affinity of cotton fabrics toward quercetin (flavonoid) dye with excellent color fastness properties. The partially purified laccase also showed anti-proliferative activity against HepG2 and MCF-7 tumor cells. However, high laccase concentration is required to estimate IC50.

CONCLUSIONS

Ceratorhiza hydrophila MK387081 is an excellent laccase producer. The partially purified laccase from Ceratorhiza hydrophila can be used in textile dyeing and printing processes as a safer alternative to the conventional hazardous mordants. Also, it can be used in preparation of cancer treatment drugs. However, further studies are needed to investigate IC50 for both cell types at higher laccase concentrations.

Characterisation of a laccase isolated from Trametes hirsuta and its application in the oligomerisation of phenolic compounds

Phenolic compounds are widely distributed in nature and industrial environment, and their detoxification or bioactive enhancement is of great value to environmental protection and industrial development. Laccases are multicopper oxidases that catalyse the oligo- or polymerisation of phenolic compounds. Identifying new laccase producers and investigating their application potential are of great importance. In this study, a white-rot fungus, Trametes hirsuta EZ1, with significantly high laccase productivity was isolated. The optimum conditions were studied for the maximum fermentation of extracellular laccase, which was achieved at 150 U/mL with a medium containing 10% strain EZ1, 7% maltodextrin, 1.5% peptone, and 0.5 mM Cu²⁺, and incubation at initial pH 6.0, 32 °C, and 180 rpm for nine days. Subsequently, a 70-kDa laccase was purified that showed activity over a wide range of temperature and pH, sensitivity to many metal ions and sodium dodecyl sulphate, and high tolerance to organic solvents. Purified laccase showed a significant unreported effect by catalysing catechol or ferulic acid into dimers, trimers, and tetramers or caffeic acid into dimers, trimers, tetramers, and pentamers. The oligomeric mixtures exhibited increased antioxidative capacity compared to that of each parent monomer, except for caffeic acid derivatives. Our study offers a novel strain source for laccase production and broadens its application in the enhancement of bioactive compounds.

Copper-induced Production of Laccases for Lignin Depolymerisation and Micropollutant Degradation by Laccase-mediator Systems

Contaminants deriving from human activities represent a constantly growing threat to our environment and have a direct impact on plant and animal health. To alleviate this ecological imbalance, biocatalysis offers a green and sustainable alternative to conventional chemical processes. Due to their broad specificity, laccases are enzymes possessing excellent potential for synthetic biotransformations in various fields as well as for the degradation of organic contaminants. Herein, we produced laccases in submerged cultures of P. ostreatus and T. versicolor in three different media. The fungi/medium combination leading to the highest enzymatic activity was malt extract (2%) + yeast extract (3%) + glucose (0.8%). Laccase production was further increased by supplementing this medium with different concentrations of Cu²⁺, which also provided a better understanding of the induction effect. Additionally, we disclose preliminary results on the interaction of laccases with mediators (ABTS and violuric acid - VA) for two main applications: lignin depolymerisation with guaiacylglycerol-β-guaiacyl ether (GBG) as lignin model and micropollutant degradation with Remazol Brilliant Blue (RBB) as enzymatic bioremediation model. Promising results were achieved using VA to increase depolymerization of GBG dimer and to enhance RBB decolorisation.

Laccases as green and versatile biocatalysts: from lab to enzyme market-an overview

Laccases are multi-copper oxidase enzymes that catalyze the oxidation of different compounds (phenolics and non-phenolics). The scientific literature on laccases is quite extensive, including many basic and applied research about the structure, functions, mechanism of action and a variety of biotechnological applications of these versatile enzymes. Laccases can be used in various industries/sectors, from the environmental field to the cosmetics industry, including food processing and the textile industry (dyes biodegradation and synthesis). Known as eco-friendly or green enzymes, the application of laccases in biocatalytic processes represents a promising sustainable alternative to conventional methods. Due to the advantages granted by enzyme immobilization, publications on immobilized laccases increased substantially in recent years. Many patents related to the use of laccases are available, however, the real industrial or environmental use of laccases is still challenged by cost-benefit, especially concerning the feasibility of producing this enzyme on a large scale. Although this is a compelling point and the enzyme market is heated, articles on the production and application of laccases usually neglect the economic assessment of the processes. In this review, we present a description of laccases structure and mechanisms of action including the different sources (fungi, bacteria, and plants) for laccases production and tools for laccases evolution and prediction of potential substrates. In addition, we both compare approaches for scaling-up processes with an emphasis on cost reduction and productivity and critically review several immobilization methods for laccases. Following the critical view on production and immobilization, we provide a set of applications for free and immobilized laccases based on articles published within the last five years and patents which may guide future strategies for laccase use and commercialization.

Amperometric Biosensors Based on Direct Electron Transfer Enzymes

The accurate determination of analyte concentrations with selective, fast, and robust methods is the key for process control, product analysis, environmental compliance, and medical applications. Enzyme-based biosensors meet these requirements to a high degree and can be operated with simple, cost efficient, and easy to use devices. This review focuses on enzymes capable of direct electron transfer (DET) to electrodes and also the electrode materials which can enable or enhance the DET type bioelectrocatalysis. It presents amperometric biosensors for the quantification of important medical, technical, and environmental analytes and it carves out the requirements for enzymes and electrode materials in DET-based third generation biosensors. This review critically surveys enzymes and biosensors for which DET has been reported. Single- or multi-cofactor enzymes featuring copper centers, hemes, FAD, FMN, or PQQ as prosthetic groups as well as fusion enzymes are presented. Nanomaterials, nanostructured electrodes, chemical surface modifications, and protein immobilization strategies are reviewed for their ability to support direct electrochemistry of enzymes. The combination of both biosensor elements-enzymes and electrodes-is evaluated by comparison of substrate specificity, current density, sensitivity, and the range of detection.

Laccase and Tyrosinase Biosensors Used in the Determination of Hydroxycinnamic Acids

In recent years, researchers have focused on developing simple and efficient methods based on electrochemical biosensors to determine hydroxycinnamic acids from various real samples (wine, beer, propolis, tea, and coffee). Enzymatic biosensors represent a promising, low-cost technology for the direct monitoring of these biologically important compounds, which implies a fast response and simple sample processing procedures. The present review aims at highlighting the structural features of this class of compounds and the importance of hydroxycinnamic acids for the human body, as well as presenting a series of enzymatic biosensors commonly used to quantify these phenolic compounds. Enzyme immobilization techniques on support electrodes are very important for their stability and for obtaining adequate results. The following sections of this review will briefly describe some of the laccase (Lac) and tyrosinase (Tyr) biosensors used for determining the main hydroxycinnamic acids of interest in the food or cosmetics industry. Considering relevant studies in the field, the fact has been noticed that there is a greater number of studies on laccase-based biosensors as compared to those based on tyrosinase for the detection of hydroxycinnamic acids. Significant progress has been made in relation to using the synergy of nanomaterials and nanocomposites for more stable and efficient enzyme immobilization. These nanomaterials are mainly carbon- and/or polymer-based nanostructures and metallic nanoparticles which provide a suitable environment for maintaining the biocatalytic activity of the enzyme and for increasing the rate of electron transport.

Stabilization-destabilization and redox properties of laccases from medicinal mushroom Ganoderma lucidum and human pathogen Yersinia enterocolitica

Laccases or benzenediol oxygen oxidoreductases (EC 1.10.3.2) are polyphenol multicopper oxidases that are known for their structural and functional diversity in various life forms. In the present study, the molecular and physico-chemical properties (redox-potential and secondary structures) of fungal laccase isozymes (FLIs) isolated from a medicinal mushroom Ganoderma lucidum were analyzed and compared with those of the recombinant bacterial laccases (rLac) obtained from different Yersinia enterocolitica strains. It was revealed that the FLIs contained His-Cys-His as the most conserved residue in its domain I Cu site, while the fourth and fifth residues were variable (Ile, Leu, or Phe). Evidently, the cyclic voltammetric measurements of Glac L2 at Type 1 Cu site revealed greater E° for ABTS/ABTS⁺ (0.312 V) and ABTS⁺/ABTS²⁺ (0.773 V) compared to the E° of rLac. Furthermore, circular dichroism-based conformational analysis revealed structural stability of the FLIs at acidic pH (3.0) and low temperature (<30 °C), while the isozymes were destabilized at neutral pH (7.0) and high-temperature conditions (>70 °C). The zymographic studies further confirmed the functional inactivation of FLIs at high temperatures (≥70 °C), predominantly due to domain unfolding. These findings provide novel insight into the evolution of the catalytic efficiency and redox properties of the FLIs, contributing to the existing knowledge regarding stress responses, metabolite production, and the biotechnological utilization of metabolites.

Kinetic characterization of purified laccase from Trametes hirsuta: a study on laccase catalyzed biotransformation of 1,4-dioxane

OBJECTIVE

Laccase is one of the best known biocatalysts which degrade wide varieties of complex molecules that are both non-cyclic and cyclic in structure. The study focused on enzyme kinetics of a purified laccase from Trametes hirsuta L. fungus and its application on biotransformation of a carcinogenic molecule 1,4-dioxane.

RESULTS

Laccase was purified from white-rot fungus T. hirsuta L. which showed specific activity of 978.34 U/mg after the purification fold of 54.08. The stable laccase activity (up to 16 h) is shown at 4-6 pH and 20-40 °C temperature range. The purified enzyme exhibited significant stability for 10 metal ions up to 10 mM concentration, except for Fe²⁺ and Hg²⁺. The Cu²⁺ ion induced laccase activity up to 142% higher than the control at 10 mM concentration. The laccase enzyme kinetic parameters K_m was 20 ± 5 µM and 400 ± 60 µM, whereas K_cat was 198.29 ± 0.18/s and 80.20 ± 1.59/s for 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) and guaiacol respectively. The cyclic ether 1,4-dioxane (100 ppm) was completely degraded in presence of purified laccase within 2 h of incubation and it was confirmed by HPLC and GC analysis. The oxidation reaction was accelerated by 25, 22, 6 and 19% in presence of 1 mM syringaldehyde, vanillin, ABTS and guaiacol mediators respectively.

CONCLUSIONS

In this study, fungal laccase (a natural biocatalyst) based degradation of synthetic chemical 1,4-dioxane was reported for the first time. This method has added advantages over the multiple methods reported earlier being a natural remedy.

Effect of UVB solar irradiation on Laccase enzyme: evaluation of the photooxidation process and its impact over the enzymatic activity for pollutants bioremediation

The multi-copper Laccase enzyme corresponds to one of the most investigated oxidoreductases for potential uses in xenobiotic bioremediation. In this work, we have investigated the photo-degradation process of Laccase from Trametesversicolor induced by UVB light and the influence on its activity over selected substrates. Laccase undergoes photo-degradation when irradiated with UVB light, and the process depends on the presence of oxygen in the medium. With the kinetic data obtained from stationary and time resolved measurements, a photo-degradation mechanism of auto-sensitization was proposed for the enzyme. Laccase generates singlet oxygen, by UVB light absorption, and this reactive oxygen species can trigger the photo-oxidation of susceptible amino acids residues present in the protein structure. The catalytic activity of Laccase was evaluated before and after UVB photolysis over hydroxy-aromatic compounds and substituted phenols which represent potential pollutants. The dye bromothymol blue, the antibiotic rifampicin and the model compound syringaldazine, were selected as substrates. The values of the kinetic parameters determined in our experiments indicate that the photo-oxidative process of Laccase has a very negative impact on its overall catalytic function. Despite this, we have not found evidence of structural damage by SDS-PAGE and circular dichroism experiments, which indicate that the enzyme retained its secondary structure. We believe that, given the importance of Laccase in environmental bioremediation, the information found about the stability of this kind of biomolecule exposed to UV solar irradiation may be relevant in the technological design and/or optimization of decontamination strategies.

Purification and properties of a laccase from the mushroom Agaricus sinodeliciosus

A homogeneous monomeric laccase (ASL) from Agaricus sinodeliciosus, with a molecular mass of 65 kDa, was isolated using ion-exchange chromatography (CM-cellulose and Q-Sepharose) and gel-filtration chromatography (Superdex 75). This laccase exhibited maximum activity at 50 °C and pH 5.0. Hg²⁺ and Cd²⁺ significantly inhibited its activity. The laccase displayed a K_m value of 0.9 mM toward 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulfonate) (ABTS). In addition to ABTS, ASL exhibited higher affinity toward o-toluidine and benzidine than other substrates. ASL is able to decolorize malachite green and Eriochrome black T.

Rapid Decay of the Native Intermediate in the Metallooxidase Fet3p Enables Controlled FeII Oxidation for Efficient Metabolism

The multicopper oxidases (MCOs) couple four 1e^- oxidations of substrate to the 4e^- reduction of O₂ to H₂O. These divide into two groups: those that oxidize organic substrates with high turnover frequencies (TOFs) up to 560 s^-1 and those that oxidize metal ions with low TOFs, ∼1 s^-1 or less. The catalytic mechanism of the organic oxidases has been elucidated, and the high TOF is achieved through rapid intramolecular electron transfer (IET) to the native intermediate (NI), which only slowly decays to the resting form. Here, we uncover the factors that govern the low TOF in Fet3p, a prototypical metallooxidase, in the context of the MCO mechanism. We determine that the NI decays rapidly under optimal turnover conditions, and the mechanism thereby becomes rate-limited by slow IET to the resting enzyme. Development of a catalytic model leads to the important conclusions that proton delivery to the NI controls the mechanism and enables the slow turnover in Fet3p that is functionally significant in Fe metabolism enabling efficient ferroxidase activity while avoiding ROS generation.

"Yellow" laccase from Sclerotinia sclerotiorum is a blue laccase that enhances its substrate affinity by forming a reversible tyrosyl-product adduct

Yellow laccases lack the typical blue type 1 Cu absorption band around 600 nm; however, multi-copper oxidases with laccase properties have been reported. We provide the first evidence that the yellow laccase isolated from Sclerotinia sclerotiorum is obtained from a blue form by covalent, but nevertheless reversible modification with a phenolic product. After separating the phenolics from the extracellular medium, a typical blue laccase is obtained. With ABTS as model substrate for this blue enzyme, a non-natural purple adduct is formed with a spectrum nearly identical to that of the 1:1 adduct of an ABTS radical and Tyr. This modification significantly increases the stability and substrate affinity of the enzyme, not by acting primarily as bound mediator, but by structural changes that also alters the type 1 Cu site. The HPLC-MS analyses of the ABTS adduct trypsin digests revealed a distinct tyrosine within a unique loop as site involved in the modification of the blue laccase form. Thus, S. sclerotiorum yellow laccase seems to be an intrinsically blue multi-copper oxidase that boosts its activity and stability with a radical-forming aromatic substrate. This particular case could, at least in part, explain the enigma of the yellow laccases.

A proposed stepwise screening framework for the selection of polycyclic aromatic hydrocarbon (PAH)-degrading white rot fungi

This study suggests a simple three-step screening protocol for the selection of white rot fungi (WRF) capable of degrading polycyclic aromatic hydrocarbons (PAHs), which combines easily applicable bioassay techniques, and verifies that protocol by evaluating the PAH degradation activity, ligninolytic enzyme secretion, and relevant gene expressions of the selected PAH-degraders. Using 120 fungal strains, a sequence of bioassay techniques was applied: Bavendamm's reaction (Step 1), remazol brilliant blue R (RBBR) decolorization (Step 2); assays for tolerance to four mixed PAHs-phenanthrene, anthracene, fluoranthene, and pyrene (Step 3). This stepwise protocol selected 14 PAH-degrading WRF, including Microporus vernicipes, Peniophora incarnata, Perenniporia subacida, Phanerochaete sordida, Phlebia acerina, and Phlebia radiata. Of these, P. incarnata exhibited the highest PAH degradative activity, ranging from 40 to > 90%, which was related to the time-variable secretions of three extracellular ligninolytic enzymes: laccase, manganese-dependent peroxidase (MnP) and lignin peroxidase (LiP). Laccase and MnP production by P. incarnata tended to be greater in the early stages of PAH degradation, whereas its LiP production became intensified with decreasing laccase and MnP production. Pilc1 and pimp1 genes encoding laccase and MnP were expressed, indicating the occurrence of extracellular enzyme-driven biodegradation of PAH by the fungal strains.

Exploiting the potential of metal and solvent tolerant laccase from Tricholoma giganteum AGDR1 for the removal of pesticides

Laccase from previously reported hardwood degrading fungus, Tricholoma giganteum AGDR1, was isolated, identified at molecular level, biochemically characterized and also utilized for pesticide degradation. Laccase gene is comprised of 3752 bp, which encompassed 742-bp of 5' flanking upstream sequence with 12 introns and 12 exons. Mature enzyme possesses 391 amino acids and signal peptide, which is determined to be monomeric protein with an apparent molecular weight of 41 kDa and 6.45 pI. Higher optimal activities were observed at 45 °C and pH 3.0 and surprisingly, it exhibited more than 20% of relative activity at pH 1.5. Purified laccase was tolerant to 100 mM of metals (i.e. Se, Pb, Cu, Cr and Cd), organic solvents (ethyl acetate, methanol, ethanol and acetone) and potent inhibitors (hydroxylamine, thiourea, NaF and Na-azide) as compared to reported laccases. It was able to degrade 29%, 7% and 72% of chlorpyrifos, profenofos and thiophanate methyl within 15 h, respectively. Molecular docking analysis revealed that higher binding efficacy of these pesticides is observed with H83, H320, A95, V384, and P366 which are presented near to the catalytic site. Based on the results, T. giganteum AGDR1 laccase can be applied for the potential remediation and industrial applications under harsh conditions.

Laccases: structure, function, and potential application in water bioremediation

The global rise in urbanization and industrial activity has led to the production and incorporation of foreign contaminant molecules into ecosystems, distorting them and impacting human and animal health. Physical, chemical, and biological strategies have been adopted to eliminate these contaminants from water bodies under anthropogenic stress. Biotechnological processes involving microorganisms and enzymes have been used for this purpose; specifically, laccases, which are broad spectrum biocatalysts, have been used to degrade several compounds, such as those that can be found in the effluents from industries and hospitals. Laccases have shown high potential in the biotransformation of diverse pollutants using crude enzyme extracts or free enzymes. However, their application in bioremediation and water treatment at a large scale is limited by the complex composition and high salt concentration and pH values of contaminated media that affect protein stability, recovery and recycling. These issues are also associated with operational problems and the necessity of large-scale production of laccase. Hence, more knowledge on the molecular characteristics of water bodies is required to identify and develop new laccases that can be used under complex conditions and to develop novel strategies and processes to achieve their efficient application in treating contaminated water. Recently, stability, efficiency, separation and reuse issues have been overcome by the immobilization of enzymes and development of novel biocatalytic materials. This review provides recent information on laccases from different sources, their structures and biochemical properties, mechanisms of action, and application in the bioremediation and biotransformation of contaminant molecules in water. Moreover, we discuss a series of improvements that have been attempted for better organic solvent tolerance, thermo-tolerance, and operational stability of laccases, as per process requirements.

Screening and production of a potential extracellular fungal laccase from Penicillium chrysogenum: Media optimization by response surface methodology (RSM) and central composite rotatable design (CCRD)

This paper describes the isolation of potent extracellular-laccase producing white-rot fungus, identified by 18 s-rRNA as Penicillium-chrysogenum and its medium optimization by central-composite-rotatable-design using RSM. The optimum laccase-activity of 6.0 U ml-1 was obtained and maximum activity of 7.9 U ml-1 was achieved by statistical-optimization of the medium at 32 °C for 5 days. The molecular-weight of the laccase was found to be 67 kDa. UV-visible absorption-spectrum analysis shows peak at 600 nm and 325 nm corresponding to the type-I Cu(II) & type-III binuclear Cu(II) pair respectively confirming presence of laccase. The sharp endothermic peak at 150 °C and three-phases of protein denaturation was observed by DSC and TGA analysis for enzyme protein. The FT-IR analysis of laccase shows band at 1405cm-1, 1656 cm-1 &3400cm-1 corresponding to amide-I band, amide-II band and amino-acid group respectively. Results of the study show the enzyme is capable of carrying-out hydrolytic-cleavage of chemical-pollutants from the industrial waste-water for providing sustainable-greener environment.

Aptitude of Oxidative Enzymes for Treatment of Wastewater Pollutants: A Laccase Perspective

Natural water sources are very often contaminated by municipal wastewater discharges which contain either of xenobiotic pollutants and their sometimes more toxic degradation products, or both, which frustrates the universal millenium development goal of provision of the relatively scarce pristine freshwater to water-scarce and -stressed communities, in order to augment their socioeconomic well-being. Seeing that both regulatory measures, as regards the discharge limits of wastewater, and the query for efficient treatment methods remain unanswered, partially, the prospects of enzymatic treatment of wastewater is advisable. Therefore, a reconsideration was assigned to the possible capacity of oxidative enzymes and the respective challenges encountered during their applications in wastewater treatment, and ultimately, the prospects of laccase, a polyphenol oxidase that oxidizes aromatic and inorganic substrates with electron-donating groups in treatment aromatic contaminants of wastewater, in real wastewater situations, since it is assumed to be a vehicle for a greener community. Furthermore, the importance of laccase-driven catalysis toward maintaining mass-energy balance, hence minimizing environmental waste, was comprehensibly elucidated, as well the strategic positioning of laccase in a model wastewater treatment facility for effective treatment of wastewater contaminants.

Mode of Action, Properties, Production, and Application of Laccase: A Review

Background and Source: Laccase belongs to the blue multi-copper oxidases, which are widely distributed in fungi and higher plants. It is present in Ascomycetes, Deuteromycetes, and Basidiomycetes and found abundantly in white-rot fungi. Applications: Laccase enzymes because of their potential have acquired more importance and application in the area of textile, pulp and paper, and food industry. Recently, it is being used in developing biosensors for detection and removal of toxic pollutants, designing of biofuel cells and medical diagnostics tool. Laccase is also being used as a bioremediation agent as they have been found potent enough in cleaning up herbicides pesticides and certain explosives in soil. Because of having the ability to oxidize phenolic, non-phenolic lignin-related compounds and highly fractious environmental pollutants, laccases have drawn the attention of researchers in the last few decades. Commercially, laccases have been used to determine the difference between codeine and morphine, produce ethanol and are also being employed in de-lignify woody tissues. We have revised patents related to applicability of laccases. We have revised all the patents related to its wide applicability. Conclusion: For fulfillment of these wide applications, one of the major concerns is to develop a system for efficient production of these enzymes at a broad scale. Research in the field of laccases has been accelerated because of its wide diversity, utility, and enzymology. This paper deals with recent trends in implementation of the laccases in all practical possibilities with the help of optimizing various parameters and techniques which are responsible for mass production of the enzyme in industries.

Immobilization of ligninolytic enzymes from white-rot fungi in cross-linked aggregates

Ligninolytic enzymes from white-rot fungi are widely used in biotechnological processes. However, the application of these enzymes as free enzymes is limited due to their instability and lack of reusability. Enzyme stabilization is therefore a major challenge in biocatalytic process research, and immobilization methods are desirable. Using cross-linked enzyme aggregates (CLEAs) such as magnetic CLEAs, porous-CLEAs and combi-CLEAs is a promising technique for overcoming these issues. Cross-linking methods can stabilize and immobilize enzymes by interconnecting enzyme molecules via multiple bonds using cross-linking agents such as glutaraldehyde. The high catalyst density and microporous assembly of CLEAs guarantee high catalyst activity, which, together with their long shelf life, operational stability, and reusability, provide a cost-efficient alternative to matrix-assisted immobilization approaches. Here, we review current progress in ligninolytic enzyme immobilization and provide a comprehensive review of CLEAs. Moreover, we summarize the use of these CLEAs for biocatalysis processes, bioremediation such as dye decolourization, wastewater treatment or pharmaceutically active compound elimination.

Multiple Reaction Monitoring for quantitative laccase kinetics by LC-MS

Laccases (EC 1.10.3.2) are enzymes known for their ability to catalyse the oxidation of phenolic compounds using molecular oxygen as the final electron acceptor. Lignin is a natural phenylpropanoids biopolymer whose degradation in nature is thought to be aided by enzymatic oxidation by laccases. Laccase activity is often measured spectrophotometrically on compounds such as syringaldazine and ABTS which poorly relate to lignin. We employed natural phenolic hydroxycinnamates having different degree of methoxylations, p-coumaric, ferulic and sinapic acid, and a lignin model OH-dilignol compound as substrates to assess enzyme kinetics by HPLC-MS on two fungal laccases Trametes versicolor laccase, Tv and Ganoderma lucidum laccase, Gl. The method allowed accurate kinetic measurements and detailed insight into the product profiles of both laccases. Both Tv and Gl laccase are active on the hydroxycinnammates and show a preference for substrate with methoxylations. Product profiles were dominated by the presence of dimeric and trimeric species already after 10 minutes of reaction and similar profiles were obtained with the two laccases. This new HPLC-MS method is highly suitable and accurate as a new method for assaying laccase activity on genuine phenolic substrates, as well as a tool for examining laccase oxidation product profiles.

Laccase-Mediated Treatment of Pharmaceutical Wastes

Laccases are versatile multi-copper enzymes belonging to the superfamily of oxidase enzymes, which have been known since the nineteenth century. Recent discoveries have refined investigators' views of the potential of laccase as a magic tool for remarkable biotechnological purposes. A literature review of the capabilities of laccases, their assorted substrates, and their molecular mechanism of action now indicates the emergence of a new direction for laccase application as part of an arsenal in the fight against the contamination of water supplies by a number of frequently prescribed medications. This chapter provides a critical review of the literature and reveals the pivotal role of laccases in the elimination and detoxification of pharmaceutical contaminants in aquatic environments and wastewaters.

Ascorbic acid sensor using a PVA/laccase-Au-NPs/Pt electrode

A surface-modified electrode, PVA/laccase-Au-NPs/Pt, was prepared to sense ascorbic acid (H₂A) in this study.

Laccase From White Rot Fungi Having Significant Role in Food, Pharma, and Other Industries

Laccases (E.C. 1.10.3.2 benzenediol: oxygen oxidoreductase) are an interesting group of N glycosylated multicopper blue oxidase enzymes and the widely studied enzyme having a broad range of substrate specificity of both phenolic and non-phenolic compounds. They are widely found in fungi, bacteria plant, insects, and in lichen. They catalyze the oxidation of various phenolic and non-phenolic compounds, with the concomitant reduction of molecular oxygen to water. They could increase productivity, efficiency, and quality of products without a costly investment. This chapter depicts the applications of laccase enzyme from white rot fungi, having various industrial (such as textile dye bleaching, paper and pulp bleaching, food includes the baking, it also utilized in fruit juice industry to improve the quality and stabilization of some perishable products having plant oils), pharmaceutical (as it has potential for the synthesis of several useful drugs such anticancerous, antioxidants, synthesis of hormone derivatives because of their high value of oxidation potential) significance.

Simple screening protocol for identification of potential mycoremediation tools for the elimination of polycyclic aromatic hydrocarbons and phenols from hyperalkalophile industrial effluents

A number of fungal strains belonging to the ascomycota, basidiomycota and zygomycota genera were subjected to an in vitro screening regime to assess their ligninolytic activity potential, with a view to their potential use in mycoremediation-based strategies to remove phenolic compounds and polycyclic aromatic hydrocarbons (PAHs) from industrial wastewaters. All six basidiomycetes completely decolorized remazol brilliant blue R (RBBR), while also testing positive in both the guaiacol and gallic acid tests indicating good levels of lignolytic activity. All the fungi were capable of tolerating phenanthrene, benzo-α- pyrene, phenol and p-chlorophenol in agar medium at levels of 10 ppm. Six of the fungal strains, Pseudogymnoascus sp., Aspergillus caesiellus, Trametes hirsuta IBB 450, Phanerochate chrysosporium ATCC 787, Pleurotus ostreatus MTCC 1804 and Cadophora sp. produced both laccase and Mn peroxidase activity in the ranges of 200-560 U/L and 6-152 U/L, respectively, in liquid media under nitrogen limiting conditions. The levels of adsorption of the phenolic and PAHs were negligible with 99% biodegradation being observed in the case of benzo-α-pyrene, phenol and p-chlorophenol. The aforementioned six fungal strains were also found to be able to effectively treat highly alkaline industrial wastewater (pH 12.4). When this wastewater was supplemented with 0.1 mM glucose, all of the tested fungi, apart from A. caesiellus, displayed the capacity to remove both the phenolic and PAH compounds. Based on their biodegradative capacity we found T. hirsuta IBB 450 and Pseudogymnoascus sp., to have the greatest potential for further use in mycoremediation based strategies to treat wastestreams containing phenolics and PAHs.

Laccase: a green catalyst for the biosynthesis of poly-phenols

Laccases (benzene diol: oxidoreductases, EC 1.10.3.2) are able to catalyze the oxidation of various compounds containing phenolic and aniline structures using dissolved oxygen in water. Laccase structural features and catalytic mechanisms focused on the polymerization of aromatic compounds are reported. A description about the most recent research on the biosynthesis of chemicals and polymers is made. Selected applications of this technology are considered as well as the advantages, shortcomings and future needs related with the use of laccases.

Degradation of Synthetic Dyes by Laccases – A Mini-Review

Laccases provide a promising future as a tool to be used in the field of biodegradation of synthetic dyes with different chemical structures. These enzymes are able to oxidize a wide range of phenolic substrates without the presence of additional co-factors. Laccases have been confirmed for their potential of synthetic dye degradation from wastewater and degradation products of these enzymatic reactions become less toxic than selected dyes. This study discusses the potential of laccase enzymes as agents for laccase-catalyzed degradation in terms of biodegradation efficiency of synthetic dyes, specifically: azo dyes, triphenylmethane, indigo and anthraquinone dyes. Review also summarizes the laccase-catalyzed degradation mechanisms of the selected synthetic dyes, as well as the degradation products and the toxicity of the dyes and their degradation products.

A High Redox Potential Laccase from Pycnoporus sanguineus RP15: Potential Application for Dye Decolorization

Laccase production by Pycnoporus sanguineus RP15 grown in wheat bran and corncob under solid-state fermentation was optimized by response surface methodology using a Central Composite Rotational Design. A laccase (Lacps1) was purified and characterized and the potential of the pure Lacps1 and the crude culture extract for synthetic dye decolorization was evaluated. At optimal conditions (eight days, 26 °C, 18% (w/w) milled corncob, 0.8% (w/w) NH₄Cl and 50 mmol·L⁻¹ CuSO₄, initial moisture 4.1 mL·g⁻¹), the laccase activity reached 138.6 ± 13.2 U·g⁻¹. Lacps1 was a monomeric glycoprotein (67 kDa, 24% carbohydrate). Optimum pH and temperature for the oxidation of 2,2’-azino-bis(3-ethylbenzthiazoline-6-sulfonate) (ABTS) were 4.4 and 74.4 °C, respectively. Lacps1 was stable at pH 3.0–8.0, and after two hours at 55–60 °C, presenting high redox potential (0.747 V vs. NHE). ABTS was oxidized with an apparent affinity constant of 147.0 ± 6.4 μmol·L⁻¹, maximum velocity of 413.4 ± 21.2 U·mg⁻¹ and catalytic efficiency of 3140.1 ± 149.6 L·mmol⁻¹·s⁻¹. The maximum decolorization percentages of bromophenol blue (BPB), remazol brilliant blue R and reactive blue 4 (RB4), at 25 or 40 °C without redox mediators, reached 90%, 80% and 60%, respectively, using either pure Lacps1 or the crude extract. This is the first study of the decolorization of BPB and RB4 by a P. sanguineus laccase. The data suggested good potential for treatment of industrial dye-containing effluents.

Preliminary studies of new strains of Trametes sp. from Argentina for laccase production ability

Oxidative enzymes secreted by white rot fungi can be applied in several technological processes within the paper industry, biofuel production and bioremediation. The discovery of native strains from the biodiverse Misiones (Argentina) forest can provide useful enzymes for biotechnological purposes. In this work, we evaluated the laccase and manganese peroxidase secretion abilities of four newly discovered strains of Trametes sp. that are native to Misiones. In addition, the copper response and optimal pH and temperature for laccase activity in culture supernatants were determined. The selected strains produced variable amounts of laccase and MnP; when Cu(2+) was added, both enzymes were significantly increased. Zymograms showed that two isoenzymes were increased in all strains in the presence of Cu(2+). Strain B showed the greatest response to Cu(2+) addition, whereas strain A was more stable at the optimal temperature and pH. Strain A showed interesting potential for future biotechnological approaches due to the superior thermo-stability of its secreted enzymes.

Purification and Characterization of a White Laccase with Pronounced Dye Decolorizing Ability and HIV-1 Reverse Transcriptase Inhibitory Activity from Lepista nuda

A strain LN07 with high laccase yield was identified as basidiomycete fungus Lepista nuda from which a white laccase without type I copper was purified and characterized. The laccase was a monomeric protein with a molecular mass of 56 kDa. Its N-terminal amino acid sequence was AIGPAADLHIVNKDISPDGF. Besides, eight inner peptide sequences were determined and lac4, lac5 and lac6 sequences were in the Cu²⁺ combination and conservation zones of laccases. HIV-1 reverse transcriptase was inhibited by the laccase with a half-inhibitory concentration of 0.65 μM. Cu²⁺ ions (1.5 mM) enhanced the laccase production and the optimal pH and temperature of the laccase were pH 3.0 and 50 °C, respectively. The Km and Vmax of the laccase using ABTS as substrate were respectively 0.19 mM and 195 μM. Several dyes including laboratory dyes and textile dyes used in this study, such as Methyl red, Coomassie brilliant blue, Reactive brilliant blue and so on, were decolorized in different degrees by the purified laccase. By LC-MS analysis, Methyl red was structurally degraded by the laccase. Moreover, the laccase affected the absorbance at the maximum wavelength of many pesticides. Thus, the white laccase had potential commercial value for textile finishing and wastewater treatment.