Desulphurization of some low-rank Turkish lignites with crude laccase produced from Trametes versicolor ATCC 200801

In this paper, data obtained during the oxidative desulphurization of some low-rank Turkish lignites with crude laccase enzyme produced from Trametes versicolor ATCC 200801 are presented. In order to optimize desulphurization conditions, effects of incubation time, pulp density, incubation temperature, medium pH, and also lignite source on the desulphurization have been examined. The values for incubation period, pulp density, temperature and pH in optimum incubation condition were found as 30 min, 5%, 35 °C, and pH 5.0, respectively. Under optimum conditions, treatment of coal samples with crude laccase has caused nearly 29% reduction in their total sulphur content. During the study, the rate of desulphurization of coal sample provided from Tunçbilek with crude laccase was found to be relatively higher than the other examined coal samples. Results of analytical assays have indicated that the treatment of coals with crude laccase has caused no change in their calorific values but reduced their sulphur emissions. 35%, 13%, and 25% reductions of pyritic sulphur, sulphate and organic sulphur in a period of 30 min were achieved, for a particle size of 200 μm under optimal conditions with enzymatic desulphurization. Also, statistical analyses such as Tukey Multiple Comparison tests and ANOVA were performed.     

漆酶催化聚合对氨基苯酚

漆酶在pH 5.0的醋酸盐缓冲溶液中催化聚合4-氨基苯酚,微型反应器中40℃持续反应10h后得到黑褐色粉末。通过UV-Vis、FT-IR、1HNMR、MALDI-TOF MS、TGA和DSC对产物的结构和性能进行表征。结果表明：所得聚合物在氯仿中不溶,在丙酮、四氢呋喃、N,N-二甲基甲酰胺和二甲基亚砜中均有良好的溶解性能。根据UV-Vis、FT-IR和1HNMR分析得知聚合物中酚羟基保留,氨基参与反应,苯环上的氢部分被取代,并且推测了可能的聚合物结构。根据MALDI-TOF MS、TGA和DSC结果分析,聚合物为低聚物,相对分子质量分布在300Da到1500Da之间,聚合度从3到14。产物的分解温度为223℃,具有良好的耐热性能。     

Laccase mediated conjugation of sugar beet pectin and the effect on emulsion stability

Laccase catalyzes intermolecular cross-links between ferulic acid of sugar beet pectin (SBP). Conjugation of SBP by laccase was confirmed by increased molecular weight, monitored by size exclusion chromatography, combined with multi-angle laser light scattering (SEC–MALLS), by reduced ferulic acid concentration detected at UV 325 nm, as well as by increased particle size. In addition, cross-linked SBP developed a more compact, branched structure as verified by a smaller root mean square (RMS) when molecular weight increased. Emulsions prepared with conjugated SBP had significantly smaller d_4,3 diameter and uniform droplet size, with more negative ζ-potential than non-treated SBP, during 30 days storage at 37 °C. The d_4,3 diameter was 5.3 μm and 3.8 μm for SBP and conjugated SBP, respectively. Covalently conjugated SBP has increased functionality and improved emulsion stability, most likely attributable to development of thick layer at the oil interface.     

Sprouting and Solid-State Bioprocessing by Rhizopus oligosporus Increase the In Vitro Antibacterial Activity of Aqueous Soybean Extracts Against Helicobacter pylori

Abstract

Helicobacter pylori infection has been implicated as a major cause of gastric inflammation, peptic ulcer disease, and gastric cancer. While antibiotics have been the mainstay of current therapies for gastrointestinal disease linked to H. pylori infection, negative side-effects and antibiotic resistance issues have strengthened the need for alternative therapeutic strategies. In the search for new antimicrobial agents, much recent research has focused on the potential of dietary phenolic compounds. In this study, soybean extracts enriched for phenolic content via sprouting or solid-state bioprocessing by the dietary fungus Rhizopus oligosporus were investigated for in vitro antibacterial activity against H. pylori. Helicobacter pylori growth inhibition by soybean extracts was increased most effectively by 2?d sprouting or 2?d R. oligosporus bioprocessing. Anti-H. pylori activity was not associated with antioxidant activity, but was linked to extracts when activity of the phenolic-polymerizing enzymes guaiacol peroxidase (in sprouted soybean extracts) and laccase (in R. oligosporus-bioprocessed soybean extracts) were the highest. This suggests the potential involvement of polymeric phenolics in the anti-H. pylori activity of soybean extracts and possible mechanisms for such action are discussed.     

Adsorption-degradation of malachite green using alkali-modified biochar immobilized laccase under multi-methods

Malachite green (MG) is an environmental persistent pollutant. The excellent adsorption capacity and enzyme carrier potential of alkali modified biochar (A-MB) are potential solutions for the treatment of MG. In this paper, laccase was immobilized onto A-MB via multi-immobilization methods. The batch adsorption equilibrium experiments were conducted to study the adsorption behavior of MG on carrier A-MB. The results showed that the adsorption of MG on A-MB followed the pseudo-second-order equation and the Langmuir isotherm model. In addition, A-MB possessed a relatively high q_max (757.58 mg/g) for MG. The comparative experiment was set up to compare the removal rate of MG on free laccase (FL) and immobilized laccase (adsorption method: A/lac@A-MB; adsorption-crosslinking method: A-C/lac@A-MB; covalent binding method: CB/lac@A-MB), the maximum removal rate of FL was 89.68 %, but the maximum removal rate of A/lac@A-MB, A-C/lac@A-MB and CB/lac@A-MB was 97.70 %, 98.77 % and 97.86 %, respectively.     

A laccase-glucose oxidase biofuel cell prototype operating in a physiological buffer

Here we report on the design and study of a biofuel cell consisting of a glucose oxidase-based anode (Aspergillus niger) and a laccase-based cathode (Trametes versicolor) using osmium-based redox polymers as mediators of the biocatalysts’ electron transfer at graphite electrode surfaces. The graphite electrodes of the device are modified with the deposition and immobilization of the appropriate enzyme and the osmium redox polymer mediator. A redox polymer [Os(4,4′-diamino-2,2′bipyridine)₂(poly{N-vinylimidazole})-(poly{N-vinylimidazole})₉Cl]Cl (E⁰′ = −0.110 V versus Ag/AgCl) of moderately low redox potential is used for the glucose oxidizing anode and a redox polymer [Os(phenanthroline)₂(poly{N-vinylimidazole})₂-(poly{N-vinylimidazole})₈]Cl₂ (E⁰′ = 0.49 V versus Ag/AgCl) of moderately high redox potential is used at the dioxygen reducing cathode. The enzyme and redox polymer are cross-linked with polyoxyethylene bis(glycidyl ether). The working biofuel cell was studied under air at 37 °C in a 0.1 M phosphate buffer solution of pH range 4.4-7.4, containing 0.1 M sodium chloride and 10 mM glucose. Under physiological conditions (pH 7.4) maximum power density, evaluated from the geometric area of the electrode, reached 16 μW/cm² at a cell voltage of 0.25 V. At lower pH values maximum power density was 40 μW/cm² at 0.4 V (pH 5.5) and 10 μW/cm² at 0.3 V (pH 4.4).     

Hydrophilic carbon nanoparticle-laccase thin film electrode for mediatorless dioxygen reduction: SECM activity mapping and application in zinc-dioxygen battery

Laccase from Cerrena unicolor was adsorbed on hydrophilic carbon nanoparticles (diameter = ca. 7.8 nm) modified with phenyl sulfonate groups and immobilized on an ITO electrode surface in a sol-gel processed silicate film. As shown by scanning electron and atomic force microscopies, the nanoparticles are evenly distributed on the electrode surface forming small aggregates of tens of nanometers in size. The mediator-free electrode exhibits significant and pH-dependent electrocatalytic activity towards dioxygen reduction. The maximum catalytic current density (95 μA cm⁻²) is obtained at pH 4.8 corresponding to maximum activity of the enzyme. Under these conditions dioxygen electroreduction commences at 0.575 V vs. Ag|AgCl_sat, a value close to the formal potential of the T1 redox centre of the laccase. The scanning electrochemical microscopy images obtained in redox competition mode exploiting mediatorless electrocatalysis show that the laccase is evenly distributed in the composite film. The obtained electrode was applied as biocathode in a zinc-dioxygen battery operating in 0.1 M McIlvaine buffer (pH 4.8). It provides 1.48 V at open circuit and a maximum power density 17.4 μW cm⁻² at 0.7 V.     

Electrochemical evaluation of electron transfer kinetics of high and low redox potential laccases on gold electrode surface

Laccases and other multicopper oxidases are reported to be able to carry out direct electron transfer reactions when immobilized onto electrode surface. This allows detailed research of their electron transfer mechanisms. We have recently characterized the kinetic properties of four laccases in homogenous solution and immobilized onto an electrode surface with respect to a set of different redox mediators. In this paper we report the direct electron transfer of four purified laccases from Trametes hirsuta (ThL), Trametes versicolor (TvL), Melanocarpus albomyces (r-MaL) and Rhus vernicifera (RvL), by trapping the proteins within an electrochemically inert polymer of tributylmethyl phosphonium chloride coating a gold electrode surface. In particular, we have characterized the steps involved in the laccases electron transfer mechanism as well as the factors limiting each step. During the voltammetric experiments, non-turnover Faradic signals with midpoint potential of about 790 and 400 mV were observed for high potential laccases, ThL and TvL, corresponding to redox transformations of the T1 site and the T2/T3 cluster of the enzyme, respectively, whereas low redox potential laccases r-MaL and RvL shown a redox couple with a midpoint potential around 400 mV. The electrocatalytic properties of these laccase modified electrodes for the reduction of oxygen have been evaluated demonstrating significative direct electron transfer kinetics. The biocatalytic activity of laccases was also monitored in the presence of a well known inhibitor, sodium azide. On the basis of the experimental results, a hypothesis about the electronic pathway for intramolecular electron transfer characterizing laccases has been proposed.     

Immobilization of laccase onto 1-aminopyrene functionalized carbon nanotubes and their electrocatalytic activity for oxygen reduction

Carbon nanotubes (CNTs) were non-covalent-functionalized with 1-aminopyrene (1-AP) and used for the first time to immobilize laccase (Lac) with the aid of glutaraldehyde (GA). The results of Fourier transform infrared (FTIR) spectra confirmed the successful modification of CNTs with 1-AP. The dispersibility of CNTs in aqueous solution was improved by the functionalization of 1-AP. The electrocatalytic properties of the Lac immobilized on the 1-AP functionalized CNTs (Lac/AP-CNTs) for oxygen reduction have been investigated by cyclic voltammetry in the presence of 2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonate) diammonium salt (ABTS) in the Britton-Robinson (B-R) buffer solution (pH 3.0). Under the same experimental condition, the Lac/AP-CNTs catalyst shows higher electrocatalytic activity and better stability than the Lac immobilized on the pristine CNTs (Lac/CNTs). Additionally, effects of the mass ratio of 1-AP to CNTs in the AP-CNTs composites, the loading mass of the Lac/AP-CNTs catalyst and the pH value of the electrolyte on the electrocatalytic activity of the Lac/AP-CNTs/glassy carbon electrode for oxygen reduction were also optimized.     

Laccase immobilization on radiation synthesized epoxy functionalized polyethersulfone beads and their application for degradation of acid dye

The enzymatic degradation of textile dyes offers an alternative approach over the conventional waste water treatment processes. Covalent immobilization of the enzymes onto insoluble supports not only permits their reusability and easy separation of enzymes from the product but also, if properly performed, may improve their activities, stability and hence reduces the cost of process. In the present work, epoxy functionalized polyethersulfone (PES) was synthesized via radiation induced polymerization of poly(2,3-epoxypropyl methacrylate) [poly(EPMA)] in PES-NMP (N-methyl-2-pyrrolidone) solution using ⁶⁰Co-gamma radiation source. Poly(EPMA)-functionalized-PES [poly(EPMA)-f-PES] beads were fabricated via phase inversion route using water as the anti solvent. Laccase was covalently immobilized on to the beads via one step-room temperature coupling reaction of amine group of enzyme with the epoxy group of poly(EPMA). Enzyme activity was assayed using 2,2′-azino-bis(3-ethylthiazoline-6-sulfonate) (ABTS) as the substrate. Effect of temperature and pH on the free and immobilized enzyme activity was studied. The immobilized laccase was successfully employed to degrade Acid Red 1 (AR1) dye in aqueous solution. Room temperature incubation of the laccase immobilized poly(EPMA)-f-PES beads with AR1 dye (∼10 ppm) resulted in ∼88% degradation of the dye over a period of 15 days.