A novel magnetically separable laccase-mediator catalyst system for the aerobic oxidation of alcohols and 2-substituted-2,3-dihydroquinazolin-4(1H)-ones under mild conditions

In this study, a magnetically reusable artificial metalloenzyme has been constructed by co-immobilization of palladium nanoparticles as a strong oxidizing catalyst and laccase as an oxygen-activating enzyme into the cavities of magnetic mesocellular foams silica (Pd-Laccase@MMCF). The combination of Pd-Laccase@MMCF and hydroquinone (HQ) act as electron-transfer mediator system and make stepwise electron transfer from substrate to molecular oxygen. This catalyst system was used for the aerobic (i) oxidation of alcohols to the corresponding carbonyl compounds and (ii) dehydrogenation of 2-substituted-2,3-dihydroquinazolin-4(1H)-ones in phosphate buffer (0.1 M, pH 4.5, 4 mL)/THF (4%, 1 mL) as solvent under mild conditions. The co-immobilization of both laccase and Pd onto high surface area mesoporous support, high catalytic activity and magnetically separable and reusable make the present catalyst system superior to other currently available electron-transfer mediator systems.     

Characterization of a Novel Laccase LAC-Yang1 from White-Rot Fungus Pleurotus ostreatus Strain Yang1 with a Strong Ability to Degrade and Detoxify Chlorophenols

In this study, a laccase LAC-Yang1 was successfully purified from a white-rot fungus strain Pleurotus ostreatus strain yang1 with high laccase activity. The enzymatic properties of LAC-Yang1 and its ability to degrade and detoxify chlorophenols such as 2,6-dichlorophenol and 2,3,6-trichlorophenol were systematically studied. LAC-Yang1 showed a strong tolerance to extremely acidic conditions and strong stability under strong alkaline conditions (pH 9–12). LAC-Yang1 also exhibited a strong tolerance to different inhibitors (EDTA, SDS), metal ions (Mn²⁺, Cu²⁺, Mg²⁺, Na⁺, K⁺, Zn²⁺, Al³⁺, Co²⁺, and metal ion mixtures), and organic solvents (glycerol, propylene glycol). LAC-Yang1 showed good stability in the presence of Mg²⁺, Mn²⁺, glycerol, and ethylene glycol. Our results reveal the strong degradation ability of this laccase for high concentrations of chlorophenols (especially 2,6-dichlorophenol) and chlorophenol mixtures (2,6-dichlorophenol + 2,3,6-trichlorophenol). LAC-Yang1 displayed a strong tolerance toward a variety of metal ions (Na²⁺, Zn²⁺, Mn²⁺, Mg²⁺, K⁺ and metal ion mixtures) and organic solvents (glycerol, ethylene glycol) in its degradation of 2,6-dichlorophenol and 2,3,6-trichlorophenol. The phytotoxicity of 2,6-dichlorophenol treated by LAC-Yang1 was significantly reduced or eliminated. LAC-Yang1 demonstrated a good detoxification effect on 2,6-dichlorophenol while degrading this compound. In conclusion, LAC-Yang1 purified from Pleurotus ostreatus has great application value and potential in environmental biotechnology, especially the efficient degradation and detoxification of chlorophenols.     

Amperometric Biosensors Based on Recombinant Bacterial Laccase CotA for Hydroquinone Determination

In this study, stable CotA laccase from Bacillus subtilis 168 was adsorbed on electrode modified with a thiol graphene‐gold nanoparticle (thGP‐AuNPs) nanocomposite film. The novel bacterial laccase biosensor was employed for quantitative detection of hydroquinone (HQ) and the electrochemical properties of this laccase biosensor were investigated. The results indicate that the immobilized CotA shows great oxidation activity towards HQ in the presence of oxygen and the biosensor shows linear electrocatalytic activity in the concentration range from 1.6 to 409.6 μM, with a detection limit of 0.3 μM. Further, the CotA modified electrode, when compared to fungal laccase‐modified biosensors, shows better alkaline stability (retaining approximately 80 % and 70 % of response current at pH 8 and 9, respectively) and reusability (retaining ～87 % of response current after 100 days). The development of this new kind of laccase on a biosensor will offer a novel tool for substance detection applications in hostile environments, especially for industrial pollutants.     

漆树漆酶的催化氧化作用——Ⅷ.四卤代氢醌的漆酶催化氧化

在静止条件下,对四卤代氢醌(TXQH_2,X=Cl、Br、I)的漆酶催化氧化行为进行了考察。结果证明,四卤代氢醌的酶反应具有几个明显特征:1)一级离解种是底物参与反应的必要形式;2)半醌自由基阴离子是反应的产物;3)半醌自由基经歧化转变成相应的对醌;4)整个反应过程呈现出连串反应属性。这些特征反映了漆酶催化氧化反应的共性。结果还表明,由于卤原子的吸电子作用不强,不能使自由电子有效地离域,生成的半醌自由基寿命短,衰减快;但在二甘醇存在下,可以有效地延缓半醌自由基的衰减,实现提高半醌自由基动力学稳定性的目的。     

Active Layer of an Oxygen Electrode Based on Nanocomposite Disperse Carbon Carrier + Laccase Material

Effect of the carbon material dispersivity on the efficiency of oxygen electroreduction by laccase immobilized on finely divided colloidal graphite (FCG) and carbon black AD-100 is studied. A highly active composite material based on FCG with laccase immobilized on it is proposed and investigated. This creates optimum conditions for direct bioelectrocatalysis by enzyme molecules. The specific oxygen reduction current calculated per enzyme molecule for nanocomposite FCG + laccase is five times that on an AD-100-based composite. Increasing the active-layer thickness, which is of importance for creating a gas-diffusion oxygen electrode, reduces specific activity of composite and only the activity of ultrathin layers is thickness-independent. This is explained by percolation restrictions on the electron transport, which reduce the number of catalytically active centers in the electrode's active layer that take part in reaction. The FCG particles are presumed to form agglomerates in the active layer. The size of the agglomerates is determined on the basis of computer-aided modeling of percolation processes and experimental data on the dependence of the specific capacitance of the active mass on the active-layer thickness. Hypotheses on the origin of percolation phenomena are put forth. One such hypothesis is that agglomerates of carbon particles are fractal clusters.     

Pulp bleaching using laccase from trametes versicolor under high temperature and alkaline conditions

Kraft pulp was delignified using laccase produced by the white rot fungusTrametes versicolor immobilized in solid support under specific conditions. The stability tests showed that this enzyme was stable for 6 h at 55°C and pH 8.0, allowing its use under pH and temperature conditions very close to those used in industrial bleaching. In this work, unbleached hardwood Kraft pulp was submitted to prebleaching using 2 U laccase/g pulp basis. Reaction time, temperature, and pH of the enzymatic treatment were investigated. Good results regarding Kappa number reduction, selectivities, and high viscosities were obtained when prebleaching was performed for 1 h at temperature of 55©C and pH 8.0 followed by alkaline extraction and ECF bleaching sequences.

     

聚马来松香乙二醇酯Cu(II)配合物固定化漆树漆酶的研究

制备了聚马来松香乙二醇酯(MEEP)Cu2 、Ni2 、Ca2 和Mg2 金属离子配合物,并分别以4种配合物为载体固定化漆树漆酶,初步探讨了反应时间对酶固定化的影响,考察了固定化酶的性质。实验结果表明,在反应温度为25℃条件下,漆树漆酶的最佳固定化时间为16h;MEEPCu2 配合物固定化酶的固定化结果较好,重复使用6次后,酶相对保留活力为55.0%;该固定化酶的最适作用温度为40℃,pH值范围为5.89~9.23,固定化漆树漆酶具有比游离酶更好的热稳定性和更广泛的pH值适用范围。     

用微量热法研究漆酶和3,4—二羟基苯甲醛的反应

用微量热法研究漆酶和３，４－二羟基苯甲醛的反应望天志＊吴鼎泉万洪文＊＊屈松生（武汉大学化学系，武汉４３００７２，＊＊华中师范大学化学系武汉）关键词漆树漆酶，微量热法，３，４－二羟基苯甲醛１９９６－０８－０８收稿，１９９６－１０－１７修回国家自然科学基...     

Laccase‐catalyzed Synthesis and Antioxidant Property of Poly(catechin)

Catechin was oxidatively polymerized by laccase in a mixture of a polar organic solvent and buffer to give a new class of flavonoid polymers. Myceliophthora laccase showed high catalytic activity for the polymerization. Using a mixed solvent of acetone and pH 5 acetate buffer efficiently produced the polymer. Under the selected conditions, DMF‐soluble polymers were obtained in good yields. Effects of reaction parameters on the yield, solubility, and molecular weight of the polymer have been systematically investigated. A radical species was detected in the polymer by ESR spectroscopy. The polymers showed greatly amplified superoxide scavenging activity and xanthine oxidase inhibitory activity compared with monomeric catechin.

Superoxide scavenging activity of poly(catechin)s, n = 3. ○: catechin, □: poly(catechin).     

CuTAPc-Fe3O4纳米复合粒子及其漆酶固定化研究

漆酶的固定化研究对基于漆酶催化的光纤生物传感器具有十分重要的意义，制备了四氨基酞菁铜(CuTAPc)-Fe3O4纳米复合粒子，并用红外(IR)、场发射扫描电镜(FEG—SEM)、X射线衍射(XRD)、能谱、粒径仪等对其进行了表征．结果表明形成了以CuTAPc包覆在Fe3O4纳米粒子表面的纳米复合粒子，粒子呈现不规则球形，且分布均匀，粒子平均粒径在50nm左右，用此纳米复合粒子通过戊二醛交联法固定了漆酶，固定后的酶比游离酶具有更好的贮存稳定性及操作稳定性，这为研制高性能的光纤生物传感器打下了较好的基础。