Affinity chromatography as a rapid and convenient method for purification of fungal laccases

High density polyethylene (HDPE) biodegradation by the fungus Cladosporium halotolerans

Polyethylene (PE) is high molecular weight synthetic polymer, very hydrofobic and hardly biodegradable. To increase polyethylene bio-degradability it is very important to find microorganisms that improve the PE hydrophilic level and/or reduce the length of its polymeric chain by oxidation. In this study, we isolated Cladosporium halotolerans, a fungal species, from the gastric system of Galleria mellonella larvae. Here, we show that C. halotolerans grows in the presence of PE polymer, it is able to interact with plastic material through its hyphae and secretes enzymes involved in PE degradation.

Multicopper oxidase laccases with distinguished spectral properties: A new outlook

Multicopper oxidases (MCOs) has a unique feature of having the presence of four Cu atoms arranged into three (Type I, II and III) spectral classification. MCOs laccase due to its broad range of substrate specificity has numerous biotechnological applications. The two types of laccases include the typical blue and the atypical white, yellow laccases which have been isolated from diverse geographical locations globally. In the present study laccases were identified using Liquid Chromatograph Mass Spectrometer Studies (LCMS) study where blue laccase exhibited homology with Trametes villosa Q99044 and Q99046 and white, yellow laccase exhibited homology with Myrothecium verrucaria OX = 1859699; Q12737 and Trametes versicolor Q12717 respectively. The spectral comparison between laccases were determined via spectroscopic analysis where UV-spectra of blue laccase from Trametes versicolor had a peak at 605 nm (Type I Cu atom) whereas in case of white and yellow laccases the peak was absent and in addition had an absorption peak at 400nm. It was followed by X-Ray Diffraction (XRD) analysis of proteins where α-helix (10°) and β-sheet (22°) structure were observed in case of all the three laccases. However, the intensity of α-helix in white and yellow laccase was stronger as compared to the blue laccase whereas the intensity of β-sheet was stronger in case of blue laccase as compared to other two laccases. Further, Fourier-transform infrared spectroscopy (FTIR) analysis was performed which enabled the analysis of proteins where α-helix (1650–1658 cm⁻¹), β-sheets (1620–1640 cm⁻¹), amide I (1700−1600 cm⁻¹) amide II (bands at under 1400 cm⁻¹) and amide A, B (bands above 3000 cm⁻¹).

Enhanced production, one-step affinity purification, and characterization of laccase from solid-state culture of Lentinus tigrinus and delignification of pistachio shell by free and immobilized enzyme

Laccase mediated bio-delignification has shown promising results for the removal of lignin from bio-wastes and for providing a sustainable future for using of lignocellulosic materials in different industries. This study reports an extracellular laccase from Lentinus tigrinus with delignification capability. The production of laccase was enhanced through a solid-state fermentation on the pistachio shell bio-waste to 172.0 U mg^-1 (8.2-fold) by one-factor-at-a-time optimizing of fermentation conditions. Laccase was purified using a new synthetic affinity resin yielding a specific activity of 543.6 U mg^-1 and a 23.9-fold purification. The purified laccase was then immobilized covalently on the large pore magnetic SBA-15. Compared to free enzyme, immobilized enzyme maintained more stable at pH 2.0-11.0 and 25-55 °C, and against organic solvents, surfactants, metal ions, and inhibitors. The activity of both forms of the enzyme was increased with Cu²⁺, Ca⁺², cetyltrimethylammonium bromide, and ethyl acetate. A 0.72 V redox potential caused enzyme specificity to various substrates. 80% of lignin content of the bio-waste was removed by 50 U mL^-1 of immobilized enzyme after 8 h fermentation and delignification efficiency was greatly increased by applying higher enzyme dosages, surfactants, and organic solvents. In addition, residual activity was more than 50% after 20 cycles of delignification. The results of delignification were confirmed by GC-MS, SEM, and composition analysis of pistachio shells. This study illustrated the notable promise of the enzyme for biotechnological and environmental applications.

A structural-chemical explanation of fungal laccase activity

Fungal laccases (EC 1.10.3.2) are multi-copper oxidases that oxidize a wide variety of substrates. Despite extensive studies, the molecular basis for their diverse activity is unclear. Notably, there is no current way to rationally predict the activity of a laccase toward a given substrate. Such knowledge would greatly facilitate the rational design of new laccases for technological purposes. We report a study of three datasets of experimental K_m values and activities for Trametes versicolor and Cerrena unicolor laccase, using a range of protein modeling techniques. We identify diverse binding modes of the various substrates and confirm an important role of Asp-206 and His-458 (T. versicolor laccase numbering) in guiding substrate recognition. Importantly, we demonstrate that experimental K_m values correlate with binding affinities computed by MMGBSA. This confirms the common assumption that the protein-substrate affinity is a major contributor to observed K_m. From quantitative structure-activity relations (QSAR) we identify physicochemical properties that correlate with observed K_m and activities. In particular, the ionization potential, shape, and binding affinity of the substrate largely determine the enzyme’s K_m for the particular substrate. Our results suggest that K_m is not just a binding constant but also contains features of the enzymatic activity. In addition, we identify QSAR models with only a few descriptors showing that phenolic substrates employ optimal hydrophobic packing to reach the T1 site, but then require additional electronic properties to engage in the subsequent electron transfer. Our results advance our ability to model laccase activity and lend promise to future rational optimization of laccases toward phenolic substrates.

Isolation, one-step affinity purification, and characterization of a polyextremotolerant laccase from the halophilic bacterium Aquisalibacillus elongatus and its application in the delignification of sugar beet pulp

The aim of the present work was to study the ability of a halophilic bacterial laccase to efficient delignification in extreme conditions. Here, a highly stable extracellular laccase showing ligninolytic activity from halophilic Aquisalibacillus elongatus is described. The laccase production was strongly influenced by NaCl and CuSO₄ and under optimal conditions reached 4.8UmL^-1. The monomeric enzyme of 75kDa was purified by a synthetic affinity column with 68.2% yield and 99.8-fold purification. The enzyme showed some valuable features viz. stability against a wide range of organic solvents, salts, metals, inhibitors, and surfactants and specificity to a wide spectrum of substrates diverse in structure and redox potential. It retained more than 50% of the original activity at 25-75°C and pH 5.0-10.0. Furthermore, the enzyme was found to be effective in the delignification of sugar beet pulp in an ionic liquid that makes it useful for industrial applications.

Modeling Based Structural Insights into Biodegradation of the Herbicide Diuron by Laccase-1 from Ceriporiopsis subvermispora

The herbicide diuron (3-(3,4-dichlorophenyl)-1,1-dimethylurea) is used in many agricultural crops and non-crop areas worldwide, leading to the pollution of the aquatic environment by soil leaching. White rot fungi and its lignin modifying enzymes, peroxidases and laccases, are responsible for its degradation. Therefore, it is of interest to explore the potential use of Ceriporiopsis subvermispora laccase (CersuLac1) in the biotransformation of this herbicide by using its enzyme laccase. However, the structure of laccase from Ceriporiopsis subvermispora is still unknown. Hence, a model of laccase was constructed using homology modeling. The model was further used to dock p-methylbenzoate in the presence of four copper ions to analyze molecular basis of its binding and interaction. The ligand-protein interaction is stereo-chemically favorable in nature. The presence of the single protonated Lys457 was necessary for catalysis, being coordinated by a cupper ion. The best pose of diuron on CersuLac1 has a theoretical Ki of 2.91 mM. This is comparable to the KM values for laccases from other organisms with similar compounds. Thus, we document the insights for the potential use of laccase from Ceriporiopsis subvermispora in the biotransfrormation of diuron.

Functionalized magnetic mesoporous silica nanoparticles: fabrication, laccase adsorption performance and direct laccase capture from Trametes versicolor fermentation broth

A simple and highly efficient protocol using magnetic mesoporous silica nanoparticles (MMSNPs) with metal affinity ligands was developed to directly capture laccase from Trametes versicolor fermentation broth. The Cu(2+)-chelated magnetic mesoporous silica nanoparticles (MMSNPs-Cu(2+)) with pore sizes ranging from 3.6 to 27.1 nm exhibited size selectivity on laccase capture from the fermentation broth, and the MMSNPs-Cu(2+) with an average pore size of 14.5 nm provided 60.6-fold purification of laccase and 114.6% recovery yield of enzyme activity. Both size selectivity of the MMSNPs and affinity of the chelated metal ion resulted in high laccase capture efficiency from the fermentation broth. The most efficient MMSNPs-Cu(2+) demonstrated no significant loss in laccase capture effectiveness following 10 reuse cycles. This simple and efficient strategy has the potential to be used for the robust and inexpensive preparation of purified laccase at the industrial scale.

Immobilization of laccase on gold, silver and indium tin oxide by zirconium–phosphonate–carboxylate (ZPC) coordination chemistry

In this paper we present a simple method allowing for stable laccase immobilization on various conducting surfaces that retains the activity of the enzyme. The strategy for laccase immobilization presented in this paper relies on Zr(4+) ion coordination chemistry that involves -COO- terminal groups present on the protein. Using a host of techniques, including surface plasmon resonance (SPR), quartz crystal microbalance (QCM) gravimetry, atomic force microscopy (AFM), surface enhanced Raman scattering (SERS), resonance Raman scattering (RR) and electrochemical techniques, we show that laccase bound to a surface coordinatively through zirconium phosphonate/carboxylate (ZPC) functionalities forms a stable enzymatic layer with the enzyme retaining its activity to a significant extent.

Inactivation of enzyme laccase and role of cosubstrate oxygen in enzymatic removal of phenol from water

Research was conducted to evaluate the potential use of laccase and its susceptibility to inactivation in an alternative enzyme-based treatment technology to remove parent phenol from buffered distilled water. Enzymatic oxidative polymerization of phenol with laccase was carried out in continuously stirred batch reactors. The reaction products were insoluble polymers, which precipitated out of the solution once their solubility limits were exceeded. The findings demonstrated that the polymeric products had significant effects on enzyme activity consumption and subsequent phenol removal. Enzyme species present in the reaction vessel were classified into enzyme remaining in the solution (type 1) and enzyme adhering to the precipitate polymers (type 2). Type 1 enzyme was more efficient in removal of phenol from solution compared with type 2. Subsequent filtration enhanced the phenol removal by removing type 2 enzyme adhering to the polymer particles and decelerating enzyme inactivation. The study also investigated the effects of available dissolved oxygen, provided through aeration and hydrogen peroxide addition, on phenol removal. Aeration and hydrogen peroxide addition increased the dissolved oxygen concentration, but had no effect on the progress curve for phenol removal.

Voltammetric determination of catalytic reaction parameters of laccase based on electrooxidation of hydroquinone and ABTS

A convenient method for the measurement of the catalytic activity of laccase is proposed based on the voltammetric determination of catalytic reaction substrates: 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonate) diammonium salt (ABTS) and 1,4-benzenediol (hydroquinone). The measurement performed using microelectrodes working under spherical diffusion conditions is both accurate and simple, and allows to monitor parallely the consumption of substrate and formation of product of the catalytic reaction. The method proposed in this paper was compared with the two generally employed procedures based on oxygen measurement by Clark electrode and on spectrophotometry. The procedure described in the present paper was found to be simpler and more reproducible results were obtained than using Clark electrode. Compared to spectrophotometry a larger range of catalytic reaction substrates can be studied including colorless compounds.

Fungal laccases – occurrence and properties

Laccases of fungi attract considerable attention due to their possible involvement in the transformation of a wide variety of phenolic compounds including the polymeric lignin and humic substances. So far, more than a 100 enzymes have been purified from fungal cultures and characterized in terms of their biochemical and catalytic properties. Most ligninolytic fungal species produce constitutively at least one laccase isoenzyme and laccases are also dominant among ligninolytic enzymes in the soil environment. The fact that they only require molecular oxygen for catalysis makes them suitable for biotechnological applications for the transformation or immobilization of xenobiotic compounds.

Characterization and immobilization of the laccase from Pleurotus ostreatus and its use for the continuous elimination of phenolic pollutants

A laccase, the only ligninolytic enzyme produced by the basidiomycete Pleurotus ostreatus strain RK 36 was purified to homogeneity and characterized. The enzyme is a monomeric protein with a molecular weight of 67 000 Da and an isoelectric point of 3.6. Type I and type III Cu(2+) centers were identified by spectrophotometry. With syringaldazine as substrate laccase showed the highest oxidation rates at pH 5.8, 50 degrees C, and in 40 mM phosphate buffer. Among the tested stabilization parameters laccase retained most of its activity in high ionic buffer, pH 10, -20 degrees C, in the presence of 10 mM benzoic acid and with 35% ethylene glycol respectively. Crude laccase was covalently immobilized to Eupergit((R))C. Benzoate was found to stabilize the enzyme during the immobilization process. The activity loss of laccase during 10 days at 25 degrees C storage was 2% on average. Continuous elimination of 2,6-dimethoxyphenol by immobilized laccase was carried out in a packed bed reactor followed by filtration of the formed precipitate. The solubility of the polymerisates of oxidized syringaldazine, o-dianisidine, and 2,6-dimethoxyphenol with respect to temperature, pH-value and organic solvents were examined. The precipitates were found to be insoluble under non-extreme environmental conditions.

Production and Characterization of Laccase from Botrytis cinerea 61-34

An isolate of Botrytis cinerea (strain 61-34) constitutively expresses substantial amounts of extracellular laccase on a defined growth medium. The enzyme has been purified to homogeneity by a facile operational sequence, the last stage of which involves hydrophobic interaction chromatography. By these means, over 80 mg of laccase liter(sup-1) can be obtained from aerated fermentor reaction broths. The enzyme, with an estimated M(infr) of 74,000 and pI of 4.0, is a monomeric glycoprotein containing 49% carbohydrate predominantly as hexose. With 2,6-dimethoxyphenol, it exhibits a pH optimum of 3.5 and a temperature optimum of 60(deg)C, and its K(infm) is 100 (mu)M. The purified enzyme with this substrate has a specific activity of 9.1 mkat mg of protein(sup-1). Taken together with a broad substrate range and its stability in 4% sodium dodecyl sulfate or 2 M urea solutions, several biotechnology transfers are suggested.

A new enzyme immobilization procedure using copper alginate gel: application to a fungal phenol oxidase

A new procedure was developed for enzyme immobilization by entrapment in copper alginate gel. The mechanical properties of the copper alginate gel were characterized and compared with those of the most widely used calcium alginate. The system was applied to the immobilization of a fungal phenol oxidase. Optimal conditions for enzyme immobilization were set up: the system immobilized 85% of the enzyme, and the remaining 15% was recovered in the aqueous immobilization medium. The stability and activity of the immobilized enzyme were studied. After immobilization, the enzyme was active in a wider pH range, the temperature of its optimal activity was shifted to lower values, and the possibility of storage at 4 degrees C was greatly improved. The immobilized enzyme generally increased the rate of oxidation of various substrates. The results indicate a potential use of this system for the construction of bioreactors to be used in the detoxification of polluted waste waters.