Presence Of 1-hydroxybenzotriazole Research Articles

Laccase-mediator system for enzymatic degradation of carbonaceous matter in the sequential pretreatment of double refractory gold ore from Syama mine, Mali

The sequential bio-treatment of refractory carbonaceous gold ore is a promising solution to recover gold effectively by environmentally friendly technology, which includes bio-oxidation of sulfide and biodegradation of carbonaceous matter by lignin-degrading enzymes. There are several drawbacks in enzyme treatment using cell-free spent medium (CFSM), including lignin peroxidase and manganese peroxidase from Phanerochaete chrysosporium, in particular the poor stability of enzyme activities. In the present work, laccase-mediator system (LMS) was applied for the degradation of carbonaceous matter in real gold ore to improve the efficiency of gold extraction as well as handling. The LMS was intended to be a great alternative process of CFSM with utilizing purified laccase in the presence of 1-hydroxybenzotriazole as a mediator. The application of LMS provided several advantages including not only greater stability, greater efficiency to degrade carbonaceous matter, better handling, much saving the treatment time, but also wider availability in laccase. In addition, replacing bio-oxidation with ferric chloride leaching as the dissolution path of sulfides facilitated avoiding the formation of jarosite and saving the required time. The gold recovery by cyanidation was improved from 41.5 ± 0.3% for the starting material to 81.3 ± 3.9% (n = 2) for the solid residues after the modified sequential pretreatment. This is correspondent to 86.3% of gold recovery for the extractable maximum gold excluding the enclosed gold in acid-insoluble silicates. The improved process involving LMS can be proposed with valuable advantages to fit a sustainable metallurgical technology of gold ores.

Bioremoval and Detoxification of Anthracene by a Halophilic Laccase from Alkalibacillus salilacus.

Polycyclic Aromatic Hydrocarbons (PAHs) as resistant compounds in the environment has received much attention in recent years due to their adverse effects on ecological health. Among the various methods studying the removal of PAHs, enzyme biotechnology is one of the most effective and appropriate method. In the present study, a halophilic laccase was used for bioremoval of anthracene in the presence of 1-Hydroxybenzotriazole (HBT). Halophilic laccase from Alkalibacillus salilacus was tested for anthracene degradation. Residual concentration of anthracene at various concentrations of NaCl (0‒4 M), incubation time, pH, solvent, and surfactants in the enzymatic reaction mixtures was determined by HPLC. The maximum removal of substrate was achieved after 72 h at 40 °C, pH 8, and NaCl concentration 1.5 M. Besides, the addition of 1% (v/v) ionic and non-ionic surfactants and 25% (v/v) of various organic solvents increased removal efficiency. The kinetic parameters Km and Vmax of the laccase for removing of anthracene were 0.114 μM and 0.546 μmoL. h.-1 mg-1, respectively. Laccase showed the maximum removal efficiency of anthracene in the presence of 1-Hydroxybenzotriazole (HBT).

Fe3O4 catalytic ozonation of iohexol degradation in the presence of 1-hydroxybenzotriazole: Performance, transformation mechanism, and pathways

This study explored the degradation of an iodine X-ray contrast media, iohexol, under heterogeneous ozone-catalyzed oxidation by adding Fe3O4 and 1-hydroxybenzotriazole (HBT). Results show that increasing the dosages of Fe3O4 catalyst and ozone as well as solution pH were beneficial to the degradation of iohexol. The presence of low background humic acid (HA) concentration (≤10 mg/L) promoted iohexol degradation, but high HA concentration (≥20 mg/L) inhibited it. Adding HBT exhibited a similar effect on iohexol degradation as HA. The degradation rate constant of iohexol was calculated as 0.07108 min−1 in the Fe3O4/O3/HBT process ([HBT] = 5 μM) at pH 7.0, which was approximately 1.5 times higher than that in the Fe3O4/O3 process (0.04533 min−1), and 4 times higher than that in the O3 process (0.01742 min−1). Fe3O4/O3/HBT process was pH-dependent with high degradation efficiency of iohexol at pH 5 or 7. Singlet oxygen (1O2), hydroxyl radical (OH∙), and superoxide radical (O2-∙) have been identified in the Fe3O4/O3/HBT process, and the conversion of Fe2+ to Fe3+ was more obvious on the surface of Fe3O4 compared to that in the Fe3O4/O3 process. Transformation intermediates were identified, and the degradation pathways of iohexol were proposed. Overall, Fe3O4/O3 could enhance iohexol degradation compared with ozone-only system, and adding trace HBT in Fe3O4/O3 system can further enhance heterogeneous ozone-catalyzed process for rapid organic matter degradation.

Degradation of Anthracene by Immobilizing Laccase From Trametes Versicolor onto Chitosan Beads and Hyacinth Plant

Polycyclic aromatic hydrocarbons (PAHs) are recognized as a toxic, mutagenic and/or carcinogenic compounds, and their pollution of soil and aquifer is of increasing environmentally risk. Laccases (E.C. 1.10.3.2) are phenoloxidases catalyze the oxidation of PAHs in the presence of a mediator compound and hyacinth plant. In this study laccase from Trametes versicolor was immobilized into chitosan, and the potential to oxidize anthracene in the presence of 1-hydroxybenzotriazole (HBT) was examined. Results indicated that the immobilization enhanced the stability of laccase against temperature, pH, inhibitors and loading time compared with the other cases. The immobilized laccase-mediator system was as efficient as the free enzyme for oxidizing the tested PAHs. After 24h. of incubation, immobilized laccase–HBT showed a system oxidization more than immobilized laccase without (HBT) of PAHs; Chitosan with hyacinth plant and (HBT) resulted better conversion than chitosan with or without HBT. These results indicate a new chance for applying the immobilized laccase in bioremediation.

Application of free and immobilized laccase for removal and detoxification of fluoroquinolones from aqueous solution

<p>Laccase from Trametes versicolor was immobilized by covalent bonds formation on CPC silica carriers. Elimination of two floroqinolone (FQ); enrofloxacine (ENR) and flumequine (FLU) using laccase in both free and immobilized form in the absence and presence of 1-hydroxybenzotriazole (HBT) and 4-Hydroxybenzoic acid (HBA) as mediators was investigated. Temperature, pH and storage stability of immobilized laccase was significantly improved compare to free laccase. In the absence of a laccase mediator, the initial concentrations of 50 mg L–1 of ENR and FLU decreased by 19 % and 28 %, respectively, after 6 h treatment using the immobilized laccase, while, the removal percentages were increased to 98 % and 96 %, respectively, when the immobilized laccase was used in presence of HBT. Whereas, the removal percentages of ENR and FLU were increased to 97 % and 88 %, respectively, when the immobilized laccase was used in presence of HBA. After twenty runs of the enzymatic elimination (laccase-HBT system) of ENR and FLU, the immobilized laccase exhibited the relative removal of 17.63 % and 15.62 %, respectively. The results of microtoxicity test (growth inhabitation percentage of six bacterial strains) showed a significant decrease in toxicity of the laccase-treated ENR and FLU solution.</p>

New Nanoaggregates of Crosslinked Laccase for Reactive Red Bioremediation.

Environmental concerns have led to an increased interest in developing green technologies for bioremediation of wastewater pollutants. In view of this, laccases have emerged as attractive green catalysts due to their applicability in oxidizing broad range of substrates. In the present work laccase was extracted from Coriolus versicolor (MTCC 138) and stabilized by formation of new crosslinked laccase nanoaggregates (CLNAs) using two different crosslinkers-N,N-methylenebisacrylamide (N, N-MBAAm) and ethyleneglycol dimethacrylate (EGDMA). Evaluation of laccase activity profile of the free as well as the well characterized CLNAs was carried out, and these were used in reactive red (RR) bioremediation. The CLNAs showed enriched catalytic activity at different temperatures and pH than the free laccase, good reusability when studied up to six cycles, and thermal and storage stability. CLNAs exhibited good bioremediation ability, which was enhanced in the presence of 1-hydroxybenzo triazole (HBT), a laccase mediator.

Preparation of synthetic auxin-amino acid conjugates

Auxin amide conjugates are regulators of the most important auxin, indole-3-acetic acid (IAA), which is considered responsible for many important processes within the plants. Herein, amide conjugates of IAA were synthesized employing a simple and efficient coupling method with WSCI·HCl, a water-soluble condensing reagent, in the presence of 1-hydroxybenzotriazole. IAA conjugates with 10 amino acids along with their corresponding methyl esters were prepared in excellent yields, up to 95%, aiming to facilitate their identification in plant species. Eight IAA-amino acid methyl ester conjugates are characterized here for the first time.

Immobilized laccase on bentonite-derived mesoporous materials for removal of tetracycline

Bentonite is a natural and environmentally clay mineral, and bentonite-derived mesoporous materials (BDMMs) were obtained conveniently from the alkali and acid treatment of bentonite. In the present study, BDMMs were explored for immobilization of laccase obtained from Trametes versicolor. As a result, bentonite-derived mesoporous materials-Laccase (BDMMs-Lac) was developed for the removal of tetracycline (TC). The enzyme immobilization process was carried out through physical adsorption contact (ion exchange adsorption, hydrogen bond adsorption, and Van der waals adsorption) between the BDMMs and laccase. The process of immobilization remarkably increased its operating temperature. The BDMMs-Lac exhibited over 60% removal efficiency for TC within 3 h in the presence of 1-hydroxybenzotriazole (HBT). In conclusion, BDMMs-Lac showed more promising potential than free laccase for practical continuous applications.

Mechanism and stereoselectivity in NHC-catalyzed β-functionalization of saturated carboxylic ester.

To understand the mechanism and origin of the stereoselectivity of the [3 + 2] annulation reaction between a carboxylic ester and an isatin generating spirooxindole lactone catalyzed by N-heterocyclic carbene (NHC), density functional theory (DFT) calculations have been carried out. DFT results indicate that the catalytic cycle begins with the coupling of the catalyst with benzotriazole ester, followed by α-deprotonation to produce the enolate intermediate. The subsequent 1,4-proton transfer affords the homoenolate intermediate. The next crucial step is the stereoselective C–C bond formation. Then proton transfer takes place leading to the formation of the lactone intermediate. Finally, the elimination of the catalyst furnishes the final product. The presence of 1-hydroxybenzotriazole (HOBt) dramatically accelerates the proton transfer step. More importantly, HOBt has a non-negligible impact on stereoselective C–C bond formation, and the SR-configured product is the major stereoisomer of the annulation product, which is in good agreement with the experimental observations. The differential π⋯π stacking, C–H⋯π, lone pair (LP)⋯π and repulsion interactions are found to be responsible for the stereoselectivity. The obtained mechanistic insights should provide valuable information for understanding the important roles of the NHC catalyst and HOBt additive and be helpful for designing better NHC catalysts for this kind of reaction.

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.

Purification and Characterization of the Laccase Involved in Dye Decolorization by the White-Rot Fungus Marasmius scorodonius.

Marasmius scorodonius secretes an extracellular laccase in potato dextrose broth, and this enzyme was purified up to 206-fold using (NH4)2SO4 precipitation and a Hi-trap Q Sepharose column. The molecular mass of the purified laccase was estimated to be ~67 kDa by SDS-PAGE. The UV/vis spectrum of the enzyme was nontypical for laccases, and metal content analysis revealed that the enzyme contains 1 mole of Fe and Zn and 2 moles of Cu per mole of protein. The optimal pH for the enzymatic activity was 3.4, 4.0, and 4.6 with 2,2'-azino-bis(3-ethylbenzothazoline-6-sulfonate) (ABTS), guaiacol, and 2,6-dimethoxy phenol as the substrate, respectively. The optimal temperature of the enzyme was 75°C with ABTS as the substrate. The enzyme was stable in the presence of some metal ions such as Ca2+, Cu2+, Ni2+, Mg2++, Mn2+, Ba2+, Co2+, and Zn2+ at a low concentration (1 mM), whereas Fe2+ completely inhibited the enzymatic activity. The enzymatic reaction was strongly inhibited by metal chelators and thiol compounds except for EDTA. This enzyme directly decolorized Congo red, Malachite green, Crystal violet, and Methylene green dyes at various decolorization rates of 63-90%. In the presence of 1-hydroxybenzotriazole as a redox mediator, the decolorization of Reactive orange 16 and Remazol brilliant blue R was also achieved.

Purification and immobilization of laccase from Trichoderma harzianum strain HZN10 and its application in dye decolorization.

In this study we report the purification of laccase produced by Trichoderma harzianum strain HZN10 (using wheat bran under solid state fermentation) and its application in decolorization of synthetic dyes. Extracellular laccase was purified to homogeneity by DEAE-Sepharose and Sephadex G-100 chromatography with specific activity of 162.5 U/mg and 25-fold purification. Purified laccase was immobilized in various entrapments like calcium alginate, copper alginate, calcium alginate–chitosan beads and sol–gel matrix. Optimization results revealed that the laccase immobilized in sol–gel was optimally active in wide pH range (4.0–7.0) and thermo-stable (50–70 °C) than free enzyme which was optimum at 50 °C and pH 6.0. Kinetic analysis showed Km of 0.5 mM and 2.0 mM and Vmax of 285 U/mg and 500 U/mg by free laccase and sol–gel immobilized laccase respectively with 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) [ABTS] substrate. Free and immobilized laccase was employed for decolorization of three different synthetic dyes (malachite green, methylene blue and congo red). High performance liquid chromatography (HPLC) analysis results revealed that approximately 100% of malachite green, 90% of methylene blue and 60% of congo red dyes at initial concentration of 200 mg/L were decolorized within 16, 18 and 20 h, respectively by laccase immobilized in sol–gel matrix in the presence of 1-hydroxybenzotriazole (HBT) mediator. During the decolorization all three synthetic dyes showed various peaks on HPLC chromatogram indicating different by-products formation. Finally, phytotoxicity analysis results revealed that the by-products of synthetic dyes (formed during decolorization) showed less toxicity against Phaseolus mungo compared to untreated synthetic dyes.

Elimination and detoxification of sulfathiazole and sulfamethoxazole assisted by laccase immobilized on porous silica beads

This study assessed the immobilization of laccase on CPC silica beads and removal of two sulfonamides, sulfathiazole (STZ) and sulfamethoxazole (SMZ), using free and immobilized laccase. The results showed that free laccase (1Uml−1) removed 66% and 77% of SMZ and STZ, respectively, in the presence of 1-hydroxybenzotriazole (1 mM) as a laccase mediator after incubation at 40 °C for 1 h. Maximum enzymatic removal of both applied sulfonamides was achieved at a temperature of 50 °C and a pH of 5. At the elevated temperature of 70 °C, immobilized laccase removed 71.7% of STZ and 53% of SMZ. After ten cycles of removal experiments, 63.3% and 82.6% of the initial activity of the immobilized laccase toward SMZ and STZ remained, respectively. A lower Km value for STZ (0.056 mM) compared to that of SMZ (0.096 mM) confirmed a higher affinity of immobilized laccase toward STZ. A microtoxicity study of the inhibition of bacterial growth showed a decrease in toxicity of the laccase-treated sulfonamide solution.

Decolorization of two synthetic dyes using the purified laccase of Paraconiothyrium variabile immobilized on porous silica beads

BackgroundDecolorization of hazardous synthetic dyes using laccases in both free and immobilized form has gained attention during the last decades. The present study was designed to prepare immobilized laccase (purified from Paraconiothyrium variabile) on porous silica beads followed by evaluation of both free and immobilized laccases for decolorization of two synthetic dyes of Acid Blue 25 and Acid Orange 7. Effects of laccase concentration, pH and temperature alteration, and presence of 1-hydroxybenzotriazole (HBT) as laccase mediator on decolorization pattern were also studied. In addition, the kinetic parameters (K m and V max ) of the free and immobilized laccases for each synthetic dye were calculated.ResultsImmobilized laccase represented higher temperature and pH stability compare to free one. 39% and 35% of Acid Blue 25 and Acid Orange 7 was decolorized, respectively after 65 min incubation in presence of the free laccase. In the case of immobilized laccase decolorization percent was found to be 76% and 64% for Acid Blue 25 and Acid Orange 7, respectively at the same time. Increasing of laccase activity enhanced decolorization percent using free and immobilized laccases. Relative decolorization of both applied dyes was increased after treatment by laccase-HBT system. After nine cycles of decolorization by immobilized laccase, 26% and 31% of relative activity were lost in the case of Acid Blue 25 and Acid Orange 7, respectively.ConclusionsTo sum up, the present investigation introduced the immobilized laccase of P. variabile on porous beads as an efficient biocatalyst for decolorization of synthetic dyes.

Separation and characterization of cellulose fibers from cypress wood treated with ionic liquid prior to laccase treatment

Separation of cellulose fibers (CFs) from woody biomass with minimal structural alteration using a “green” and efficient method was achieved by treatment with the ionic liquid (IL), [emim][OAc] (1-ethyl-3-methylimidazolium acetate) at 80°C for 1h. The IL was recovered by rinsing with water–acetone mixture prior to treatment of the wood with Trametes sp. laccase in the presence of 1-hydroxybenzotriazole as a mediator. IL pretreatment did not significantly change the chemical composition of the wood, but did alter its structure and rendered its surface more accessible to the enzyme. Treated and untreated samples were characterized by SEM, FTIR, XRD, TGA, and chemical methods. The cellulose content of the produced fibers was approximately 73.1% and the lignin content was 9.8%, much lower than the lignin content of 29.3% of the untreated wood. The cellulose fibers exhibited higher cellulose crystallinity and better thermal stability compared to untreated wood materials.

Preparation of starch–sodium lignosulfonate graft copolymers via laccase catalysis and characterization of antioxidant activity

Graft copolymers of waxy maize starch and sodium lignosulfonate (SLS) were prepared by Trametes versicolor laccase catalysis in aqueous solution. Amount of SLS grafted based on phenol analysis was 0.5% and 1.0% in the absence and presence of 1-hydroxybenzotriazole (HBT), respectively. Starch–SLS graft copolymers were effective antioxidants as judged by 2,2′-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity. The presence of laccase caused a reduction in starch molecular weight although a cross-linked gel fraction was also observed when HBT was present. This new method for preparing starch chemically modified with phenolic compounds is simple and the resulting antioxidant polymers have potential in food, cosmetic and packaging applications.

Decolorization of malachite green by laccase: Optimization by response surface methodology

The potential of banana peel as a solid-substrate for the production of extracellular laccase by the white-rot fungus Pleurotus florida NCIM 1243 was studied in this paper. Response surface methodology (RSM) was applied to optimize the decolorization of the malachite green (MG) dye by partially purified laccase obtained from P. florida. We observed that the presence of 1-hydroxybenzotriazole (HBT) enhances the decolorization of MG. Four variables namely, dye (MG), enzyme (laccase), redox mediator (HBT) and time (h) were used in this study to optimize significant correlation between the effects of these variables on the decolorization of MG using RSM. It was observed that the variables MG, laccase, HBT and time were found to be 95.80ppm, 2.16U/ml, 0.85mM and 3.02h, respectively, for maximum (about 96%) decolorization of MG dye. A quadratic model was developed through RSM in terms of related independent variables to describe the dye decolorization rate as the response. The experimental values were in good agreement with the predicated ones and the model was highly significant. The toxicity test was performed; the root growth inhibition of Allium cepa was depending on the dye concentration.

Laccase/HBT and laccase-CBM/HBT treatment of softwood kraft pulp: Impact on pulp bleachability and physical properties

Pycnoporus cinnabarinus laccase and a chimeric laccase-CBM were applied in softwood kraft pulp biobleaching in the presence of 1-hydroxybenzotriazole (HBT). The presence of CBM could enhance the laccase biobleaching potential as a decrease in the enzymatic charge and chlorine dioxide consumption, as well as an increase in pulp brightness were observed. Laccase/HBT treatment could be improved by increasing oxygen pressure from 1 to 3bar and pulp consistency from 5% to 10%. Conversely, under the same conditions, no improvement of laccase-CBM/HBT treatment was observed, indicating a different behavior of both systems. However, laccase-CBM/HBT treatment led to a better preservation of pulp properties. This effect was probably due to fiber surface modifications involving the action of the CBM. Transmission electron microscopy examination of pulp fibers indicated a retention of laccase-CBM inside the pulp fibers due to CBM binding and an increased external microfibrillation of the fibers due to enzymatic treatments.

Treatment of tetracycline antibiotics by laccase in the presence of 1-hydroxybenzotriazole

Tetracycline antibiotics are widely used in human and veterinary medicine; however, residual amounts of these antibiotics in the environment are of concern since they could contribute to selection of resistant bacteria. In this study, tetracycline (TC), chlortetracycline (CTC), doxycycline (DC) and oxytetracycline (OTC) were treated with laccase from the white rot fungus Trametes versicolor in the presence of the redox mediator 1-hydroxybenzotriazole (HBT). High performance liquid chromatography demonstrated that DC and CTC were completely eliminated after 15min, while TC and CTC were eliminated after 1h. This system also resulted in a complete loss of inhibition of growth of Escherichia coli and Bacillus subtilis and the green alga Pseudokirchneriella subcapitata with decreasing tetracycline antibiotic concentration. These results suggest that the laccase–HBT system is effective in eliminating tetracycline antibiotics and removing their ecotoxicity.

Postsynthetic Modification of Oligonucleotides with Imidazophenazine Dye and its Effect on Duplex Stability

Carboxyalkyl derivative of the intercalating agent imidazo[4,5-b]phenazine was used for the postsynthetic oligonucleotide modification. Model pentadecathymidylate-imidazophenazine conjugate was prepared from 5′-aminoalkyl-modified (dT)15 by using phosphonium coupling reagent BOP in the presence of 1-hydroxybenzotriazole. Spectral-fluorescent properties of the conjugate were studied. The attachment of the dye was found to increase the thermal stability of (dT)15 duplex with poly(dA) by more than 4°C, probably by the intercalation mechanism.