Purification and characterization of a novel laccase from Cerrena sp. HYB07 with dye decolorizing ability

Biodegradation of bisphenol A by a Pichia pastoris whole-cell biocatalyst with overexpression of laccase from Bacillus pumilus and investigation of its potential degradation pathways

Bisphenol A (BPA), an endocrine disrupter with estrogen activity, can infiltrate animal and human bodies through the food chain. Enzymatic degradation of BPA holds promise as an environmentally friendly approach while it is limited due to lower stability and recycling challenges. In this study, laccase from Bacillus pumilus TCCC 11568 was expressed in Pichia pastoris (fLAC). The optimal catalytic conditions for fLAC were at pH 6.0 and 80 °C, with a half-life T1/2 of 120 min at 70 °C. fLAC achieved a 46 % degradation rate of BPA, and possible degradation pathways were proposed based on identified products and reported intermediates of BPA degradation. To improve its stability and degradation capacity, a whole-cell biocatalyst (WCB) was developed by displaying LAC (dLAC) on the surface of P. pastoris GS115. The functionally displayed LAC demonstrated enhanced thermostability and pH stability along with an improved BPA degradation ability, achieving a 91 % degradation rate. Additionally, dLAC maintained a degradation rate of over 50 % after the fourth successive cycles. This work provides a powerful catalyst for degrading BPA, which might decontaminate endocrine disruptor-contaminated water through nine possible pathways.

Characterization of a Novel Fe2+ Activated Non-Blue Laccase from Methylobacterium extorquens

Herein, a novel laccase gene, Melac13220, was amplified from Methylobacterium extorquens and successfully expressed in Escherichia coli with a molecular weight of approximately 50 kDa. The purified Melac13220 had no absorption peak at 610 nm and remained silent within electron paramagnetic resonance spectra, suggesting that Melac13220 belongs to the non-blue laccase group. Both inductively coupled plasma spectroscopy/optical emission spectrometry (ICP-OES) and isothermal titration calorimetry (ITC) indicated that one molecule of Melac13220 can interact with two iron ions. Furthermore, the optimal temperature of Melac13220 was 65 °C. It also showed a high thermolability, and its half-life at 65 °C was 80 min. Melac13220 showed a very good acid environment tolerance; its optimal pH was 1.5. Cu²⁺ and Co²⁺ can slightly increase enzyme activity, whereas Fe²⁺ could increase Melac13220′s activity five-fold. Differential scanning calorimetry (DSC) indicated that Fe²⁺ could also stabilize Melac13220. Unlike most laccases, Melac13220 can efficiently decolorize Congo Red and Indigo Carmine dyes even in the absence of a redox mediator. Thus, the non-blue laccase from Methylobacterium extorquens shows potential application value and may be valuable for environmental protection, especially in the degradation of dyes at low pH.

Evaluation of Antioxidant Potential of Commercial Cinnamon Samples and Its Vasculature Effects

Growing concerns on free radicals are the oxidative processes associated with physiological damage. The consumption of functional foods and use of plants with antioxidant capacity are widespread. Given the importance of determining antioxidant capacity in relation to the therapeutic effect, this study was aimed at evaluating cinnamon extract (Cinnamomum sp.) in commercial samples by spectrophotometric and voltammetric methods and assessing the vascular activity of some samples. The spectrophotometric methods performed were DPPH (1,1-diphenyl-2-picrihydrazine), ABTS (2,21-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid)), and Folin-Ciocalteu radical sequestration assays. For the electrochemical experiments, a three-electrode system was used, consisting of carbon paste electrode, platinum wire, and Ag/AgCl/KClsat, representing the working, auxiliary, and reference electrodes, respectively. The electroanalytical methods used were differential pulse, square wave, and cyclic voltammetries. The extracts were prepared in hydroalcoholic solution. A calibration curve with gallic acid was calculated to quantify their equivalent amounts in the analyzed extract. The correlation between the electrochemical approach and the total phenols calculated by the ABTS, DPPH, and Folin-Ciocalteu methods was 0.63, 0.7, and 0.73, respectively, with 1 being an ideal directly proportional correlation. The correlation between spectrophotometric methods was 0.83. A biosensor was developed in a carbon paste electrode using the enzyme laccase, obtained by the fungus Marasmiellus colocasiae. It was observed that the antioxidant profile of the cinnamon samples had an analytical sign improvement of up to 4 times when compared with the electrode without the modification. The samples were analyzed by mass spectrometer, and the main chemical markers found were coumarin, cinnamaldehyde, and eugenol. Pharmacological trials showed that these samples also induce a significant vasorelaxant effect associated to antioxidant potential on vascular injury induced by oxidative stress. Thus, cinnamon showed a high antioxidant capacity, in agreement with the results obtained in other studies, emphasizing its importance as a functional food.

The production of laccases by white-rot fungi under solid-state fermentation conditions

Laccases (E.C. 1.10.3.2) produced by white-rot fungi (WRF) can be widely used, but the high cost prevents their use in large-scale industrial processes. Finding a solution to the problem could involve laccase production by solid-state fermentation (SSF) simulating the natural growth conditions for WRF. SSF offers several advantages over conventional submerged fermentation (SmF), such as higher efficiency and productivity of the process and pollution reduction. The aim of this review is therefore to provide an overview of the current state of knowledge about the laccase production by WRF under SSF conditions. The focus is on variations in the up-stream process, fermentation and down-stream process and their impact on laccase activity. The variations of up-stream processing involve inoculum preparation, inoculation of the medium and formulation of the propagation and production media. According to the studies, the production process can be shortened to 5-7 days by the selection of a suitable combination of lignocellulosic material and laccase producer without the need for any additional components of the culture medium. Efficient laccase production was achieved by valorisation of wastes as agro-food, municipal wastes or waste generated from wood processing industries. This leads to a reduction of costs and an increase in competitiveness compared to other commonly used methods and/or procedures. There will be significant challenges and opportunities in the future, where SSF could become more efficient and bring the enzyme production to a higher level, especially in new biorefineries, bioreactors and biomolecular/genetic engineering.

A Brief History of Colour, the Environmental Impact of Synthetic Dyes and Removal by Using Laccases

The history of colour is fascinating from a social and artistic viewpoint because it shows the way; use; and importance acquired. The use of colours date back to the Stone Age (the first news of cave paintings); colour has contributed to the social and symbolic development of civilizations. Colour has been associated with hierarchy; power and leadership in some of them. The advent of synthetic dyes has revolutionized the colour industry; and due to their low cost; their use has spread to different industrial sectors. Although the percentage of coloured wastewater discharged by the textile; food; pharmaceutical; cosmetic; and paper industries; among other productive areas; are unknown; the toxic effect and ecological implications of this discharged into water bodies are harmful. This review briefly shows the social and artistic history surrounding the discovery and use of natural and synthetic dyes. We summarise the environmental impact caused by the discharge of untreated or poorly treated coloured wastewater to water bodies; which has led to physical; chemical and biological treatments to reduce the colour units so as important physicochemical parameters. We also focus on laccase utility (EC 1.10.3.2), for discolouration enzymatic treatment of coloured wastewater, before its discharge into water bodies. Laccases (p-diphenol: oxidoreductase dioxide) are multicopper oxidoreductase enzymes widely distributed in plants, insects, bacteria, and fungi. Fungal laccases have employed for wastewater colour removal due to their high redox potential. This review includes an analysis of the stability of laccases, the factors that influence production at high scales to achieve discolouration of high volumes of contaminated wastewater, the biotechnological impact of laccases, and the degradation routes that some dyes may follow when using the laccase for colour removal.

Screening of Novel Laccase Producers-Isolation and Characterization of Cold-Adapted Laccase from Kabatiella bupleuri G3 Capable of Synthetic Dye Decolorization

Psychrophilic laccases catalyzing the bond formation in mild, environmentally friendly conditions are one of the biocatalysts at the focus of green chemistry. Screening of 41 cold-adapted strains of yeast and yeast-like fungi revealed a new laccase-producing strain, which was identified as Kabatiella bupleuri G3 IBMiP according to the morphological characteristics and analysis of sequences of the D1/D2 regions of 26S rDNA domain and the ITS1-5,8S-ITS2 region. The extracellular activity of laccase in reaction with 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) at the optimal pH 3.5 was 215 U/L after 15 days of growth in a medium with waste material and 126 U/L after 25 days of cultivation in a defined medium. Copper (II) ions (0.4 mM), Tween 80 (1.0 mM) and ascorbic acid (5.0 mM) increased the production of laccase. The optimum temperature for enzyme operation is in the range of 30-40 °C and retains over 60% of the maximum activity at 10 °C. New laccase shows high thermolability-half-life at 40 °C was only 60 min. Enzyme degradation of synthetic dyes was the highest for crystal violet, i.e., 48.6% after 1-h reaction with ABTS as a mediator. Outcomes of this study present the K. bupleuri laccase as a potential psychrozyme for environmental and industrial applications.

Tailor-made novel electrospun polystyrene/poly(d,l-lactide-co-glycolide) for oxidoreductases immobilization: Improvement of catalytic properties under extreme reaction conditions

Immobilized enzymes find applications in many areas such as pharmacy, medicine, food production and environmental protection. However, protecting these biocatalysts against harsh reaction conditions and retaining their enzymatic activity even after several biocatalytic cycles are major challenges. Properly selected supports and type of surface modifier therefore seem to be crucial for achieving high retention of catalytic activity of immobilized biomolecules. Here we propose production of novel composite electrospun fibers from polystyrene/poly(d,l-lactide-co-glycolide) (PS/PDLG) and its application as a support for immobilization of oxidoreductases such as alcohol dehydrogenase (ADH) and laccase (LAC). Two strategies of covalent binding, (i) (3-aminopropyl)triethoxysilane (APTES) with glutaraldehyde (GA) and (ii) polydopamine (PDA), were applied to attach oxidoreductases to PS/PDLG. The average fiber diameter was shown to increase from 1.252 µm to even 3.367 µm after enzyme immobilization. Effective production of PS/PDLG fibers and biomolecule attachment were confirmed by Fourier transform infrared spectroscopy analysis. The highest substrate conversion efficiency was observed at pH 6.5 and 5 for ADH and LAC, respectively, and at 25 °C for enzymes attached using the APTES + GA approach. Improvement of enzyme stabilization at high temperatures was confirmed in that relative activities of enzymes immobilized onto PS/PDLG fibers were over 20% higher than those of the free biomolecules, and enzyme leaching from the support using acetate and MES buffers was below 10 mg/g.

Immobilization of yeast cell walls with surface displayed laccase from Streptomyces cyaneus within dopamine-alginate beads for dye decolorization

High amounts of toxic textile dyes are released into the environment due to coloring and wastewaters treatment processes' inefficiency. To remove dyes from the environment and wastewaters, researchers focused on applying immobilized enzymes due to mild reaction conditions and enzyme nontoxicity. Laccases are oxidases with wide substrate specificity, capable of degradation of many different dye types. Laccase from Streptomyces cyaneus was expressed on the surface of Saccharomyces cerevisiae EBY100 cells. The specific activity of surface-displayed laccase was increased by toluene-induced lysis to 3.1 U/g of cell walls. For cell wall laccase immobilization within hydrogel beads, alginate was modified by dopamine using periodate oxidation and reductive amination and characterized by UV-Vis, FTIR, and NMR spectroscopy. Cell wall laccase was immobilized within alginate and dopamine-alginate beads additionally cross-linked by oxygen and laccase. The immobilized enzyme's specific activity was two times higher using dopamine-alginate compared to native alginate beads, and immobilization yield increased 16 times. Cell wall laccase immobilized within dopamine-alginate beads decolorized Amido Black 10B, Reactive Black 5, Evans Blue, and Remazol Brilliant Blue with 100% efficiency and after ten rounds of multiple-use retained decolorization efficiency of 90% with Evans Blue and 61% with Amido Black.

Partial purification and characterization of a thermophilic and alkali-stable laccase of Phoma herbarum isolate KU4 with dye-decolorization efficiency

Production of an extracellular thermophilic and alkali stable laccase from Phoma herbarum isolate KU4 was reported for the first time, both in submerged fermentation (SmF, highest 1590 U/mL) and solid state fermentation (SSF, highest 2014.21 U/mL) using agro-industrial residues. The laccase was partially purified to 7.93 fold with the apparent molecular weight of 298 kDa. The enzyme had pH optimum at 5.0 and temperature optimum at 50 °C, with maximum stability at pH 8.0. It showed activity towards various phenolic and non-phenolic compounds. The kinetic parameters, K_m, V_max and K_cat of the laccase for DMP were 0.216 mM, 270.27 U/mg and 506.69 s^-1, respectively. Laccase activity was inhibited by various metal ions and conventional inhibitors, however, it was slightly increased by Zn²⁺. The laccase showed good decolorization efficiency towards four industrial dyes, namely, methyl violet (75.66%), methyl green (65%), indigo carmine (58%) and neutral red (42%) within 24 h. FTIR analysis of the decolorized products confirmed the degradation of the dyes. The decolorization efficiency of the enzyme suggests that the partially purified laccase could be used to decolorize synthetic dyes present in industrial effluents and for waste water treatments. The thermophilic and alkali stable laccase may also have wider potential industrial applications.

A highly thermotolerant laccase produced by Cerrena unicolor strain CGMCC 5.1011 for complete and stable malachite green decolorization

Laccases are a class of multi-copper oxidases with important industrial values. A thermotolerant laccase produced by a basidiomycete fungal strain Cerrena unicolor CGMCC 5.1011 was studied. With glycerin and peptone as the carbon and nitrogen sources, respectively, a maximal laccase activity of 121.7 U/mL was attained after cultivation in the shaking flask for 15 days. Transcriptomics analysis revealed an expressed laccase gene family of 12 members in C. unicolor strain CGMCC 5.1011, and the gene and cDNA sequences were cloned. A glycosylated laccase was purified from the fermentation broth of Cerrena unicolor CGMCC 5.1011 and corresponded to Lac2 based on MALDI-TOF MS/MS identification. Lac2 was stable at pH 5.0 and above, and was resistant to organic solvents. Lac2 displayed remarkable thermostability, with half-life time of 1.67 h at 70 ºC. Consistently, Lac2 was able to completely decolorize malachite green (MG) at high temperatures, whereas Lac7 from Cerrena sp. HYB07 resulted in accumulation of colored MG transformation intermediates. Molecular dynamics simulation of Lac2 was conducted, and possible mechanisms underlying Lac2 thermostability were discussed. The robustness of C. unicolor CGMCC 5.1011 laccase would not only be useful for industrial applications, but also provide a template for future work to develop thermostable laccases.

A New Laccase of Lac 2 from the White Rot Fungus Cerrena unicolor 6884 and Lac 2-Mediated Degradation of Aflatoxin B1

Aflatoxin B₁ (AFB₁) is a known toxic human carcinogen and can be detoxified by laccases, which are multicopper oxidases that convert several environmental pollutants and toxins. In this study, a new laccase that could catalyze AFB₁ degradation was purified and identified from the white-rot fungus Cerrena unicolor 6884. The laccase was purified using (NH₄)₂SO₄ precipitation and anion exchange chromatography, and then identified as Lac 2 through zymogram and UHPLC-MS/MS based on the Illumina transcriptome analysis of C. unicolor 6884. Six putative laccase protein sequences were obtained via functional annotation. The lac 2 cDNA encoding a full-length protein of 512 amino acids was cloned and sequenced to expand the fungus laccase gene library for AFB₁ detoxification. AFB₁ degradation by Lac 2 was conducted in vitro at pH 7.0 and 45 °C for 24 h. The half-life of AFB₁ degradation catalyzed by Lac 2 was 5.16 h. Acetosyringone (AS), Syrinagaldehyde (SA) and [2,2' -azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid)] (ABTS) at 1 mM concentration seemed to be similar mediators for strongly enhancing AFB₁ degradation by Lac 2. The product of AFB₁ degradation catalyzed by Lac 2 was traced and identified to be Aflatoxin Q₁ (AFQ₁) based on mass spectrometry data. These findings are promising for a possible application of Lac 2 as a new aflatoxin oxidase in degrading AFB₁ present in food and feeds.

Comparison of downstream processing methods in purification of highly active laccase

Laccases have received the attention of researchers in the last few decades due to their ability to degrade phenolic and lignin-related compounds. This study aimed at obtaining the highest possible laccase activity and evaluating the methods of its purification. The crude laccase from bioreactor cultivation of Cerrena unicolor fungus was purified using ultrafiltration, aqueous two-phase extraction (ATPE) and foam fractionation (FF), which allowed for the assessment of these three downstream processing (DSP) methods. The repeated fed-batch cultivation mode applied for the enzyme production resulted in a high laccase specific activity in fermentation broth of 204.1 U/mg. The use of a specially constructed spin filter inside the bioreactor enabled the integration of enzyme biosynthesis and biomass filtration in one apparatus. Other methods of laccase concentration and purification, namely ATPE and FF, proved to be useful for laccase separation; however, the efficiency of FF was rather low (recovery yield of 24.9% and purification fold of 1.4). Surprisingly, the recovery yield after ATPE in a PEG 6000-phosphate system in salt phase was higher (97.4%) than after two-step ultrafiltration (73.7%). Furthermore, it was demonstrated that a simple, two-step purification procedure resulted in separation of two laccase isoforms with specific activity of 2349 and 3374 U/mg. All in all, a compact integrated system for the production, concentration and separation of fungal laccases was proposed.

Rotating magnetic field as tool for enhancing enzymes properties - laccase case study

The aim of this study was to analyse the effect of rotating magnetic field (RMF) exposition on the fungal laccase catalytic properties. The results obtained in the study revealed that RMF may positively alter the laccase activity. A significant increase in activities of 11%, 11%, and 9% were observed at 10 Hz, 40 Hz and 50 Hz, respectively. Exposure of laccase to the rotating magnetic field resulted in its increased activity at broader pH range and a slight shift in optimum pH from 4.0 to 4.5 at RMF with frequency 20 Hz. The results show that the enzyme activity, stability, and optimum pH can be significantly altered depending on the characteristic of the applied RMF. Application of rotating magnetic field opens a new way for controlling and directions of enzyme-based bioprocessing.

A novel homodimer laccase from Cerrena unicolor BBP6: Purification, characterization, and potential in dye decolorization and denim bleaching

The white-rot fungus Cerrena unicolor BBP6 produced up to 243.4 U mL-1 laccase. A novel laccase isoform LacA was purified; LacA is a homodimer with an apparent molecular mass of 55 kDa and an isoelectric point of 4.7. Its optimal pH was 2.5, 4.0, and 5.5 when 2, 2'-Azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS), guaiacol, and 2, 6-dimethoxyphenol (2, 6-DMP) were used as the substrates, respectively. The optimal temperature was 60°C for ABTS and 80°C for both guaiacol and 2, 6-DMP. LacA retained 82-92% activity when pH was greater than 4 and 42%-92% activity at or below 50°C. LacA was completely inhibited by 0.1 mM L-cysteine, 1 mM Dithiothreitol, and 10 mM metal ions, Ca2+, Mg2+ and Co2+. LacA had good affinity for ABTS, with a Km of 49.1 μM and a kcat of 3078.9 s-1. It decolorized synthetic dyes at 32.3-87.1%. In the presence of 1-hydroxybenzotriazole (HBT), LacA decolorized recalcitrant dyes such as Safranine (97.1%), Methylene Blue (98.9%), Azure Blue (96.6%) and simulated textile effluent (84.6%). With supplemented manganese peroxidase (MnP), Mn2+ and HBT, the purified LacA and BBP6 fermentation broth showed great potential in denim bleaching, with an up to 5-fold increase in reflectance values.

Fungal Laccase Efficiently Destains Coomassie Brilliant Blue-R-250 Stained Polyacrylamide Gels

Fungal laccase-mediated destaining of Coomassie Brilliant Blue-R-250 stained polyacrylamide electrophoretic gel is very sensitive and environment friendly. Fermenting of Cerrena sp. HYB07 yields a broth with laccase activity which when supplemented with distilled water and used as a destaining solution results in a clear gel background in 2 h at 37 °C. Also, separation of the laccase enzyme for efficient functioning is not required. The method utilizes gel destaining and process of decolorizing dye simultaneously with a detection sensitivity of up to 10 ng. This technique avoids the use of hazardous organic compounds, as the destaining solution and the destain solution could be discarded easily without any further treatment.

Kinetic analysis and structural studies of a high-efficiency laccase from Cerrena sp. RSD1

A high‐efficiency laccase, DLac, was isolated from Cerrena sp. RSD1. The kinetic studies indicate that DLac is a diffusion‐limited enzyme. The crystal structure of DLac was determined to atomic resolution, and its overall structure shares high homology to monomeric laccases, but displays unique substrate‐binding loops from those in other laccases. The substrate‐binding residues with small side chain and the short substrate‐binding loop IV broaden the substrate‐binding cavity and may facilitate large substrate diffusion. Unlike highly glycosylated fungal laccases, the less‐glycosylated DLac contains one highly conserved glycosylation site at N432 and an unique glycosylation site at N468. The N‐glycans stabilize the substrate‐binding loops and the protein structure, and the first N‐acetylglucosamine is crucial for the catalytic efficiency. Additionally, a fivefold increase in protein yield is achieved via the submerged culture method for industrial applications.

Database

The atomic coordinates of the structure of DLac from Cerrena sp. RSD1 and structural factors have been deposited in the RCSB Protein Data Bank (PDB ID: 5Z1X).

Expression and characterization of novel laccase gene from Pandoraea sp. ISTKB and its application

In the present study, a non-blue laccase gene from previously reported lignin degrading bacterium, Pandoraea sp. ISTKB, was isolated, cloned and expressed in E. coli. Bioinformatics analysis of sequence discovered twin-arginine translocation signal sequence, copper binding motifs and presence of more random coil compare to helices and sheets in structure. The enzyme was found to be active on wide pH range and the pH optima was observed at pH 4 and 8 on substrate 2,2'-Azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) and 2,6-Dimethoxyphenol respectively. This is a thermophilic enzyme with maximum activity around 50-70 °C. The enzyme was further characterized by spectroscopy, reaction kinetics and effect of metal ions and inhibitors were studied. Compared to laccase alone; the treatment of dyes with laccase plus mediator resulted in enhanced decolorization of crystal violet, methylene blue, azure B, carmine and Congo red but the effect of mediator was not observed on trypan blue. Laccase treatment triggered polymerization on vanillic acid (VA) and kraft lignin (KL). Laccase plus mediator treatment reversed the polymerization and resulted in transformation or degradation of VA and KL. This thermophilic and alkalophilic non-blue laccase from Pandoraea sp. ISTKB is promising with prospective biotechnological application.

Isolation, identification of a laccase-producing fungal strain and enzymatic properties of the laccase

A new type of thermostable laccase was isolated from Paraphoma sp. GZS18, and its partial enzymatic properties were determined. A strain GZS18 of laccase with high yield was screened from forest soil and identified as Paraphoma sp. GZS18 through morphological characteristics and ITS sequence analysis. The laccase of Paraphoma sp. GZS18 (Lac-P) was obtained through cation-anion exchange chromatography, gel filtration chromatography, and other purification processes. The testing result shows that Lac-P is a single protein of 75 kDa, and the 11 amino acid sequences in the N-terminal are AX^aVSVASREMT (X^a was the non-standard protein). The optimum temperature and optimum pH of lac-P activity are substrate-independent. The temperature is in the range of 50-70 °C, and pH has high catalytic efficiency in the acidic range. Lac-P has good stability in the temperature and pH. The half time at 70-60 °C is 1.5 and 4 h, respectively. At pH 6-9 and room temperature, there is more than 80% activity 24 h later. Lac-P is tolerant of most metal ions and low concentrations of inhibitors but is inhibited by Hg²⁺, Fe²⁺ and NaN₃. The laccase from Paraphoma sp. GZS18 at high temperature and pH 6-9, with strong stability, has better industrial application characteristics.

Expression of a new laccase from Moniliophthora roreri at high levels in Pichia pastoris and its potential application in micropollutant degradation

Laccases have gained significant attention due to their emerging applications including bioremediation, biomass degradation and biofuel cells. One of the prerequisites for the industrial application of laccases is their sufficient availability. However, expression levels of recombinantly expressed laccases are often low. In this study Mrl2, a new laccase from the basidiomycete Moniliophthora roreri, was cloned in Pichia pastoris and produced in an optimized fed-batch process at an exceptionally high yield of 1.05 g l⁻¹. With a redox potential of 0.58 V, Mrl2 belongs to mid-redox potential laccases. However, Mrl2 demonstrated high k_cat values of 316, 20, 74, and 36 s⁻¹ towards 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS), syringaldazine (SGZ), 2,6-dimethoxyphenol (2,6-DMP) and guaiacol, respectively. Mrl2 remained stable above pH 6 and in the presence of many metal ions, which is important for application in bioremediation. Mrl2 was investigated for the ability to degrade endocrine disrupting chemicals (EDCs) and non-steroidal anti-inflammatory drugs (NSDAIs) at neutral pH value. The enzyme accepted and converted estrone, 17β-estradiol, estriol, the synthetic contraceptive 17α-ethinyl estradiol and bisphenol A at pH 7 faster than high-potential laccases from Trametes versicolor. For example, within 30 min Mrl2 removed more than 90% bisphenol A, 17ß-estradiol, 17α-ethinyl estradiol and estriol, respectively. The concentration of the recalcitrant drug diclofenac dropped by 56% after 20 h incubation with Mrl2.

Immobilized Cerrena sp. laccase: preparation, thermal inactivation, and operational stability in malachite green decolorization

Laccases are polyphenol oxidases with widespread applications in various industries. In the present study, the laccase from Cerrena sp. HYB07 was immobilized with four methods, namely entrapment in alginate, covalently binding to chitosan as well as formation of cross-linked enzyme aggregates (CLEAs) and magnetic CLEAs (M-CLEAs). The activity recovery rates of the immobilized laccases ranged from 29% to 68%. Immobilization elevated the reaction temperature optimum and reduced substrate specificity, but not necessarily the turnover rate. pH stability of immobilized laccases was improved compared with that of the free laccase, especially at acidic pH values. Thermal inactivation of all laccases followed a simple first-order exponential decay model, and immobilized laccases displayed higher thermostability, as manifested by lower thermal inactivation rate constants and longer enzyme half-life time. Operational stability of the immobilized laccase was demonstrated by decolorization of the triphenylmethane dye malachite green (MG) at 60 °C. MG decolorization with free laccase was accompanied by a shift of the absorption peak and accumulation of a stable, colored intermediate tetradesmethyl MG, probably due to lower thermostability of the free laccase and premature termination of the degradation pathway. In contrast, complete decolorization of MG was achieved with laccase CLEAs at 60 °C.

A halotolerant laccase from Chaetomium strain isolated from desert soil and its ability for dye decolourization

A novel fungal laccase produced by the ascomycete Chaetomium sp. isolated from arid soil was purified and characterized and its ability to remove dyes was determined. Extracellular laccase was purified 15-fold from the crude culture to homogeneity with an overall yield of 50% using ultrafiltration and anion-exchange chromatography. The purified enzyme was found to be a monomeric protein with a molecular mass of 68 kDa, estimated by SDS-PAGE, and with an isoelectric point of 5.5. The optimal temperature and pH value for laccase activity toward 2,6-DMP were 60 °C and 3.0, respectively. It was stable at temperatures below 50 °C and at alkaline conditions. Kinetic study showed that this laccase showed higher affinity on ABTS than on 2,6-DMP. Its activity was enhanced by the presence of several metal ions such as Mg2+, Ca2+ and Zn2+, while it was strongly inhibited by Fe2+, Ag+ and Hg2+. The novel laccase also showed high, remarkable sodium chloride tolerance. Its ability to decolorize different dyes, with or without HBT (1-hydroxy-benzotriazole), as redox mediator, suggests that this protein may be useful for different industrial applications and/or bioremediation processes.

A novel multicopper oxidase (laccase) from cyanobacteria: Purification, characterization with potential in the decolorization of anthraquinonic dye

A novel extracellular laccase enzyme produced from Spirulina platensis CFTRI was purified by ultrafiltration, cold acetone precipitation, anion exchange and size exclusion chromatography with 51.5% recovery and 5.8 purification fold. The purified laccase was a monomeric protein with molecular mass of ~66 kDa that was confirmed by zymogram analysis and peptide mass fingerprinting. The optimum pH and temperature of the enzyme activity was found at 3.0 and 30°C using ABTS as substrate but the enzyme was quite stable at high temperature and alkaline pH. The laccase activity was enhanced by Cu+2, Zn+2 and Mn+2. In addition, the dye decolorization potential of purified laccase was much higher in terms of extent as well as time. The purified laccase decolorized (96%) of anthraquinonic dye Reactive blue- 4 within 4 h and its biodegradation studies was monitored by UV visible spectra, FTIR and HPLC which concluded that cyanobacterial laccase can be efficiently used to decolorize synthetic dye and help in waste water treatment.

Degradation of tetracycline by immobilized laccase and the proposed transformation pathway

Magnetic cross-linked enzyme aggregates (M-CLEAs) were prepared for Cerrena laccase and used in antibiotic treatment. Of the seven antibiotics examined in this study, Cerrena laccase M-CLEAs were most effective in degradation of tetracycline (TC) and oxytetracycline (OTC), followed by ampicillin, sulfamethoxazole and erythromycin. The redox mediator ABTS was not able to improve efficiencies of degradation of TC and OTC. Cerrena laccase at 40U/mL eliminated 100μg/mL TC at pH 6 and 25°C in 48h in the absence of a redox mediator, with over 80% degradation occurring within the first 12h. Laccase treatment also significantly suppressed the antimicrobial activity of TC and OTC. Three TC transformation products, the levels of which initially increased and subsequently decreased during laccase treatment were identified by using LC-TOF MS. A mechanism of laccase-mediated TC oxidation was proposed based on the identified intermediates.

Laccase Gene Family in Cerrena sp. HYB07: Sequences, Heterologous Expression and Transcriptional Analysis

Laccases are a class of multi-copper oxidases with industrial potential. In this study, eight laccases (Lac1-8) from Cerrena sp. strain HYB07, a white-rot fungus with high laccase yields, were analyzed. The laccases showed moderate identities to each other as well as with other fungal laccases and were predicted to have high redox potentials except for Lac6. Selected laccase isozymes were heterologously expressed in the yeast Pichia pastoris, and different enzymatic properties were observed. Transcription of the eight laccase genes was differentially regulated during submerged and solid state fermentation, as shown by quantitative real-time polymerase chain reaction and validated reference genes. During 6-day submerged fermentation, Lac7 and 2 were successively the predominantly expressed laccase gene, accounting for over 95% of all laccase transcripts. Interestingly, accompanying Lac7 downregulation, Lac2 transcription was drastically upregulated on days 3 and 5 to 9958-fold of the level on day 1. Consistent with high mRNA abundance, Lac2 and 7, but not other laccases, were identified in the fermentation broth by LC-MS/MS. In solid state fermentation, less dramatic differences in transcript abundance were observed, and Lac3, 7 and 8 were more highly expressed than other laccase genes. Elucidating the properties and expression profiles of the laccase gene family will facilitate understanding, production and commercialization of the fungal strain and its laccases.

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.

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.

Optimal parameters for laccase-mediated destaining of Coomassie Brilliant Blue R-250-stained polyacrylamide gels

The data presented in this article are related to the research article entitled “Destaining of Coomassie Brilliant Blue R-250-stained polyacrylamide gels with fungal laccase” [1]. Laccase is a class of multicopper oxidases that can catalyze oxidation of recalcitrant dyestuffs. This article describes optimal parameters for destaining of polyacrylamide gels, stained with Coomassie Brilliant Blue R-250, with laccase from basidiomycete Cerrena sp. strain HYB07. Effects of laccase activity, mediator type and concentration, temperature and time on destaining of polyacrylamide gels were evaluated with respect to gel background intensity and protein band signals, and the optimal destaining effects were obtained with 15 U mL⁻¹ laccase and 2 μM ABTS at 37 °C after 2 h.

Laccase Production and Differential Transcription of Laccase Genes in Cerrena sp. in Response to Metal Ions, Aromatic Compounds, and Nutrients

Laccases can oxidize a wide range of aromatic compounds and are industrially valuable. Laccases often exist in gene families and may differ from each other in expression and function. Quantitative real-time polymerase chain reaction (qPCR) was used for transcription profiling of eight laccase genes in Cerrena sp. strain HYB07 with validated reference genes. A high laccase activity of 280.0 U/mL was obtained after submerged fermentation for 5 days. Laccase production and laccase gene transcription at different fermentation stages and in response to various environmental cues were revealed. HYB07 laccase activity correlated with transcription levels of its predominantly expressed laccase gene, Lac7. Cu²⁺ ions were indispensable for efficient laccase production by HYB07, mainly through Lac7 transcription induction, and no aromatic compounds were needed. HYB07 laccase synthesis and biomass accumulation were highest with non-limiting carbon and nitrogen. Glycerol and inorganic nitrogen sources adversely impacted Lac7 transcription, laccase yields, and fungal growth. The present study would further our understanding of transcription regulation of laccase genes, which may in turn facilitate laccase production as well as elucidation of their physiological roles.

Destaining of Coomassie Brilliant Blue R-250-stained polyacrylamide gels with fungal laccase

An enzyme-based method for destaining polyacrylamide gels stained with Coomassie Brilliant Blue R-250 is described. Distilled water supplemented with diluted fermentation broth of a laccase-producing white-rot fungus, Cerrena sp., was used for gel destaining, and a clear gel background was obtained in 2 h at 37 °C. Sensitivity of protein detection was 10 ng. The method did not require organic solvents or changing the destaining solution. Due to simultaneous gel destaining and dye decolorization, the colorless destaining solution can be disposed of directly. Laccase destaining of polyacrylamide gels was simple, efficient, and environmentally friendly.

Investigating the degradation process of kraft lignin by β-proteobacterium, Pandoraea sp. ISTKB

The present study investigates the kraft lignin (KL) degrading potential of novel alkalotolerant Pandoraea sp. ISTKB utilizing KL as sole carbon source. The results displayed 50.2 % reduction in chemical oxygen demand (COD) and 41.1 % decolorization after bacterial treatment. The maximum lignin peroxidase (LiP) and manganese peroxidase (MnP) activity detected was 2.73 and 4.33 U ml(-1), respectively, on day 3. The maximum extracellular and intracellular laccase activities observed were 1.32 U ml(-1) on day 5 and 4.53 U ml(-1) on day 4, respectively. The decolorization and degradation was maximum on day 2. Further, it registered an increase with the production of extracellular laccase. This unusual trend of decolorization and degradation was studied using various aromatic compounds and dyes. SEM and FTIR results indicated significant change in surface morphology and functional group composition during the course of degradation. Gas chromatography and mass spectroscopy (GC-MS) analysis confirmed KL degradation by emergence of new peaks and the identification of low molecular weight aromatic intermediates in treated sample. The degradation of KL progressed through the generation of phenolic intermediates. The identified intermediates implied the degradation of hydroxyphenyl, ferulic acid, guaiacyl, syringyl, phenylcoumarane, and pinoresinol components commonly found in lignin. The degradation, decolorization, and GC-MS analysis indicated potential application of the isolate Pandoraea sp. ISTKB in treatment of lignin-containing pollutants and KL valorization.

Laccase-catalyzed decolorization of malachite green: performance optimization and degradation mechanism

Malachite green (MG) was decolorized by laccase (LacA) of white-rot fungus Cerrena sp. with strong decolorizing ability. Decolorization conditions were optimized with response surface methodology. A highly significant quadratic model was developed to investigate MG decolorization with LacA, and the maximum MG decolorization ratio of 91.6% was predicted under the conditions of 2.8 U mL(-1) LacA, 109.9 mg L(-1) MG and decolorization for 172.4 min. Kinetic studies revealed the Km and kcat values of LacA toward MG were 781.9 mM and 9.5 s(-1), respectively. UV-visible spectra confirmed degradation of MG, and the degradation mechanism was explored with liquid chromatography-mass spectrometry (LC-MS) analysis. Based on the LC-MS spectra of degradation products, LacA catalyzed MG degradation via two simultaneous pathways. In addition, the phytotoxicity of MG, in terms of inhibition on seed germination and seedling root elongation of Nicotiana tabacum and Lactuca sativa, was reduced after laccase treatment. These results suggest that laccase of Cerrena was effective in decolorizing MG and promising in bioremediation of wastewater in food and aquaculture industries.

A novel laccase from basidiomycete Cerrena sp.: Cloning, heterologous expression, and characterization

A novel laccase gene Lac1 and its cDNA were cloned from a white-rot fungus Cerrena sp. and characterized. The 1554-bp cDNA of Lac1 encoded a mature protein with 497 amino acids, preceded by a signal peptide of 20 amino acids. An unconventional intron splice site and incomplete splicing variants of Lac1 were observed. Lac1 was heterologously expressed in the yeast host Pichia pastoris, and a maximal laccase activity of 6.3UmL(-1) in the fermentation broth was achieved after fermentation for 9 days. The recombinant protein rLac1 was purified, and its enzymatic properties and functional characteristics were investigated. When ABTS was used as the substrate, the enzyme was most active at pH 3.5 and 55°C, and stable at pH 4-10 and 20-60°C. The Km and kcat values of rLac1 toward ABTS were 28.9 μM and 332.4s(-1), respectively. Furthermore, rLac1 was tolerant to common metal ions up to 100mM concentration and capable of decolorizing structurally different dyes in the absence of a redox mediator. Hence, Lac1 may be useful for industrial applications, such as dye decolorization and bioremediation.