Transformation of 3,5-dimethoxy-4-hydroxy cinnamic acid and its derivatives using enzyme from white-rot fungus Trametes versicolor: Enzyme characteristics and its application

Transformation of 3,5-dimethoxy-4-hydroxy cinnamic acid (sinapic acid), sinapaldehyde, sinapine and sinapoyl in the model system containing an enzyme secreted by the fungus Trametes versicolor was investigated. The affinity of this enzyme was highest for sinapic acid followed by sinapaldehyde and sinapine. The optimum temperature and pH for these transformations were 50°C and pH 3·3, 50°C and pH 4·5, 60°C and pH 4·0 for sinapaldehyde, sinapine, and sinapic acid, respectively. The apparent heat of the enzyme-sinapic acid complex formation is −2557·6 J mol⁻¹. Higher concentrations of sinapine and sinapic acid caused enzyme inhibition. When canola meal was treated with this enzyme the phenolics content in this commodity was decreased by 90%.     

草酸酯合成研究进展

简述草酸及草酸酯合成的传统方法。着重介绍一氧化碳催化氧化偶联制草酸酯的发展历史、技术原理及工艺研究的进展情况。     

Overview of the pulp and paper industry from a chemical industry perspective

The major processes of the pulp and paper industry are overviewed with particular emphasis given to existing chemical requirements; processing trends are identified which may affect future chemical requirements. The pulp and paper industry represents a vast market for chemicals. On the papermaking side, overall chemical usage will probably increase due to ever greater product sophistication and emphasis on value-added grades. On the pulping side, the pressing needs for fibre conservation and more effective utilization of fibre sources can only be achieved through continuing exploitation of chemical developments.     

纸浆漂白废水中可吸附有机氯化物的特性研究进展

纸浆漂白废水中含有的可吸附有机氯化物是国内外造纸工业严控的废物,是造纸环保界关注的重点。在查阅资料基础上,对目前关于纸浆漂白废水中可吸附有机氯化物的成分、分布、生成以及降解特性等方面的研究进行了述评,重点介绍了纸浆漂白废水中可吸附有机氯化物的生成及降解性能方面的研究成果,并在此基础上对今后的研究趋势进行了展望。     

Simulating the impact of kraft pulping and bleaching parameters on Eucalyptus camaldulensis pulp properties using MATLAB

In this work, Eucalyptus camaldulensis was evaluated as the raw material for chemical pulp under different pulping and bleaching conditions. The pulping was carried out at different H‐factors, and at different effective alkalis. The resulting pulps were then oxygen delignified and bleached using various dosages of bleaching chemicals in a D₀EpD₁ sequence. The effect of independent variables (pulping or bleaching variables) on dependent variables (pulp properties) was analysed based on the multivariable least square method via MATLAB software. An agreement was found between the results predicted from the models and the experimental data. To obtain a kappa number of 15, the optimum pulping conditions were a temperature of 155°C, a time of 225 min, and an EA of 23%. Also, the hexenuronic acid (HexA) content of cooked pulp was significantly decreased in the chlorine dioxide bleaching stages, and was only marginally related to the final HexA content of bleached pulps.     

Synergism of enzymes in chemical pulp bleaching from an industrial point of view: A critical review

Enzymes are biological catalysts and are very specific, catalyzing either a single chemical reaction or a limited number of closely related reactions. For example, xylanases are enzymes that catalyze the cleavage of polymeric xylan and thereby break down this hemicellulose. The first xylanase enzyme preparations used in the bleaching process of chemical pulp also contained cellulase, which catalyzes the hydrolysis of cellulose. This obviously had an adverse effect on pulp yield and quality. Unfortunately, this setback gave enzyme-assisted pulp bleaching a negative reputation. At a later stage, enzyme producers managed to engineer enzyme production strains that generated cellulase-free xylanase preparations. However, due to the initial negative experiences with the earlier enzyme mixtures, only a limited number of companies in the pulp industry have seriously considered using these so-called second-generation enzymes in their bleach plants. It is apparent that these improved enzyme preparations would bring about significant benefits in terms of chemical cost savings and effluent quality. In addition to xylanase-aided bleaching, it is possible to improve the effectivity further by adding other enzymes, such as lipase and esterase, to create an enzyme cocktail. This may be particularly beneficial in the bleaching of hardwood pulp, such as white birch, which often encounters complex and troublesome problems with wood extractives. By adding different types of enzymes at more than one position in the fiberline, even further improvements are possible. The main objective of this review is to discuss the advantages of incorporating modern enzyme preparations in the bleaching of chemical pulp.     

Continuous biobleaching of black liquor from the pulp and paper industry using an immobilized cell system

Three different support materials have been screened for immobilization of Phanerochaete chrysosporium for biobleaching of anaerobically digested black liquor. Of these, jute rope-immobilized P. chrysosporium showed better performance than cotton and wheat carriers in terms of decolorization and COD reduction. Process parameters such as temperature, mycelial load, pH, glucose concentration and retention time were optimized using jute-immobilized fungus and the optimal values recorded were 40°C, 340 mg, 5·5, 1% (w/v) and 72 h, respectively. Continuous biobleaching of anaerobically digested black liquor using a packed bed reactor system carrying the jute-immobilized fungal biomass was successfully carried out over a period of 21 days. © 1998 Society of Chemical Industry     

Optimized design of wastewater treatment systems: Application to the mechanical pulp and paper industry: I. Design and cost relationships

Four different end-of-pipe waste-treatment processes applicable to mechanical pulp and paper manufacture were modelled. Calculated costs for an average mill were capital $34–$44 million, operating cost $3.5–$6 million/year and discounted (10 years) $60–$85 million. Compared with mill reported values, capital and operating costs of activated sludge treatment (AST) were higher by 17 and 29%, respectively; those for aerated stabilization basin (ASB) were higher by 27 and 180%. Major variables affecting the costs were BOD and TSS levels and the wastewater-to-pulp ratio. It was concluded that ASB is more economical than AST and that anaerobic treatment plus AST could be advantageous at high BOD levels.     

Immobilization of the Laccases from Trametes versicolor and Streptomyces coelicolor on Single‐wall Carbon Nanotube Electrodes: A Molecular Dynamics Study

In this work, we investigate the immobilization of laccases from Trametes versicolor (TvL) and the small laccase (SLAC) from Streptomyces coelicolor on single‐wall carbon nanotube (SWCNT) surfaces. SLAC may potentially offer improved adsorption on the electrode, thus improving bioelectrocatalytic activity via direct electron transfer (DET). Laccase immobilization on SWCNTs is achieved non‐covalently with a molecular tether (1‐pyrene butanoic acid, succinimidyl ester) that forms an amide bond with an amine group on the laccase surface while the pyrene coordinates to the SWCNT by π–π stacking. In our approach, density functional theory calculations were first used to model the interaction energies between SWCNTs and pyrene to validate an empirical force field, thereafter applied in molecular dynamics (MD) simulations. In the simulated models, the SWCNT was placed near the region of the (type 1) Cu(T1) atom in the laccases, and in proximity to other regions where adsorption seems likely. Calculated interaction energies between the SWCNTs and laccases and distances between the SWCNT surface and the Cu(T1) atom have shown that SWCNTs adsorb more strongly to SLAC than to TvL, and that the separation between the SWCNTs and Cu(T1) atoms is smaller for SLAC than for TvL, having implications for improved DET.     

废纸苯酚液化及生成树脂的结构表征

首先在一定液化工艺条件下,对废纸进行了液化处理,而后对液化后的产物分别进行了傅立叶转换红外光谱(FTIR)以及电子扫描电镜(SEM)的测定分析,并对其生成树脂进行差热(DTA)分析。FTIR的结果表明,液化废纸结构发生了明显变化,而且出现了化学组分中的最基本结构单元,表明苯酚液化处理使废纸发生了降解、酚化等化学反应。SEM测定结果表明,液化后的废纸液化中依然含有废纸的未完全液化的微小废纸组织碎片,废纸纤维结构被进一步破坏。对废纸液化树脂差热(DTA)分析的结果表明,废纸液化物树脂峰顶温度低于传统酚醛树脂;废纸液化物树脂和传统酚醛树脂一样,顶峰温度随着升温速率提高。     

Protein engineering loops in aspartic proteinases: site-directed mutagenesis, biochemical characterization and X-ray analysis of chymosin with a replaced loop from rhizopuspepsin

The loop exchange mutant chymosm 155–164 rhizopuspepsinwas expressed in Trichoderma reesei and exported into the mediumto yield a correctly folded and active product. The biochemicalcharacterization and crystal structure determination at 2.5Å resolution confirm that the mutant enzyme adopts a nativefold. However, the conformation of the mutated loop is unlikethat in native rhizopuspepsin and involves the chelation ofa water molecule in the loop. Kinetic analysis using two syntheticpeptide substrates (six and 15 residues long) and the naturalsubstrate, milk, revealed a reduction in the activity of themutant enzyme with respect to the native when acting on boththe long peptide substrate and milk. This may be a consequenceof the different charge distribution of the mutated loop, itsincreased size and/or its different conformation.     

Experimental characterization of the self-healing of cracks in an ultra high performance cementitious material: Mechanical tests and acoustic emission analysis

Self-healing of cracks in an ultra high performance concrete, considered as a model material, is investigated in this paper. An experimental program is carried out in order to quantify the phenomenon, which has been mainly highlighted by means of water permeability tests until now. Mechanical behaviour of self-healed concrete under three points bending, and acoustic emission analysis of the cracking mechanisms are reported. The mechanical tests demonstrate a recovery of the global stiffness, depending on the time of healing, for specimens initially cracked and then self-healed, and a slow improvement of structural strength. The acoustic emission (AE) analysis is performed in order to show that the mechanical response is due to new crystals precipitating in the crack. The microcracking of these products during three points bending tests is highlighted and an energy analysis provides insights about the cracking process of healed concrete, including damage of the newly formed crystals and continuation of the crack propagation.     

Estradiol Favors the Formation of Eicosapentaenoic Acid (20:5n-3) and n-3 Docosapentaenoic Acid (22:5n-3) from Alpha-Linolenic Acid (18:3n-3) in SH-SY5Y Neuroblastoma Cells

Whether neurosteroids regulate the synthesis of long chain polyunsaturated fatty acids in brain cells is unknown. We examined the influence of 17-β-estradiol (E2) on the capacity of SH-SY5Y cells supplemented with α-linolenic acid (ALA), to produce eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA). Cells were incubated for 24 or 72 h with ALA added alone or in combination with E2 (ALA + E2). Fatty acids were analyzed by gas chromatography of ethanolamine glycerophospholipids (EtnGpl) and phosphatidylcholine (PtdCho). Incubation for 24 h with ALA alone increased EPA and DPA in EtnGpl, by 330 and 430% compared to controls (P < 0.001) and DHA by only 10% (P < 0.05). Although DHA increased by 30% (P < 0.001) in ALA + E2-treated cells, the difference between the ALA and ALA + E2 treatments were not significant after 24 h (Anova-1, Fisher’s test). After 72 h, EPA, DPA and DHA further increased in EtnGpl and PtdCho of cells supplemented with ALA or ALA + E2. Incubation for 72 h with ALA + E2 specifically increased EPA (+34% in EtnGpl, P < 0.001) and DPA (+15%, P < 0.001) compared to ALA alone. Thus, SH-SY5Y cells produced membrane EPA, DPA and DHA from supplemental ALA. The formation of DHA was limited, even in the presence of E2. E2 significantly favored EPA and DPA production in cells grown for 72 h. Enhanced synthesis of ALA-elongation products in neuroblastoma cells treated with E2 supports the hypothesis that neurosteroids could modulate the metabolism of PUFA.     

Involvement of various amino- and carboxyl-terminal residues in the active site of the histidine-containing protein HPr of the phosphoenolpyruvate-dependent phosphotransferase system of Staphylococcus carnosus: site-directed mutagenesis with the ptsH gene, biochemical characterization and NMR studies of the mutant proteins

The phosphocarrier HPr (heat stable protein) of Staphylococcuscarnosus was modified by site-directed mutagenesis of the correspondingptsH gene in order to analyse the importance of amino acidswhich were supposed to be part of the active centre of the protein.Three residues which are conserved in all HPrs, Argl7, Prol8and Glu84, were mutated: Argl7 was changed to His (17RH) andPro18 and Glu84 were changed into Ala (18PA and 84EA). In addition,Leu86 was changed into Ala (86LA) and one mutant protein wasmissing the last six residues of the HPr (83). The wild typegene and all mutant genes were overexpressed and the gene productspurified to homogeneity. Three-dimensional structures of wildtype and mutant proteins were monitored by NMR spectroscopy.All five mutant HPrs had native conformations. The ATP-dependentHPr kinase can phosphorylate all HPr derivatives at Ser46. ThePTS activity of the amino-terminal HPr mutant proteins 17RHand 18PA was different compared to wild type HPr. In contrast,the car boxy-terminal mutant HPrs possessed a similar enzymeactivity to the wild type HPr. The 17RH and 18PA HPrs with substitutionnear the active centre His15 showed a very slow phosphorylationby enzyme I but the further transfer of the phosphoryl groupto enzyme III was also strongly inhibited. The enzyme activityof the HPr 17RH was significantly improved at low pH. NMR pH-titrationexperiments showed that Arg17 is not responsible for the lowpK_a, of the active centre His15 but this positively chargedresidue is essential in this position for the HPr activity.     

Kinetics and reaction mechanism of template polymerization investigated by conductimetric measurements Part 4. Radical polymerization of acrylic acid in the presence of poly(vinyl alcohol): characterization of resulting polymer blends

The radical polymerization of acrylic acid in the presence of poly(vinyl alcohol) as a template in aqueous solution has been studied using conductimetry, which shows template influences on the reaction rate. A comparison is made between data obtained by differential scanning calorimetry and infrared spectroscopy for poly(acrylic acid)–poly(vinyl alcohol) blends prepared either by template polymerization or by casting of the preformed polymers. Evidence for more significant interpolymer interactions in blends prepared by template polymerization than in those obtained by simple mixing is given. © 2001 Society of Chemical Industry     

Cobalt-exchanged mordenites: preparation,characterization and catalytic activity for the abatement of NO with CH<Subscript>4</Subscript> in the presence of excess O<Subscript>2</Subscript>

The abatement of NO with methane in the presence of oxygen was studied on various commercial MOR in the Na-form (Na-MOR) and H-form (H-MOR), or exchanged to various extents with cobalt (Co-MOR). The sodium and cobalt contents were determined by atomic absorption. Samples were characterized by FTIR and volumetric measurements of CO adsorption. Chemical analysis indicated that one cobalt species replaced two Brønsted acid sites in H-MOR and two Na⁺ ions in Na-MOR. The IR analysis of the OH stretching region, evidencing an unexpected presence of Brønsted acid sites (band at 3610 cm^?1) in Co-MOR, indicated that the exchange process had a more complex stoichiometry. The adsorption of CO at RT on Co-MOR, in addition to the bands of the corresponding H-MOR and Na-MOR matrices, yielded two types of Co^II-carbonyls, the first type occupied the?mordenite main channels, and the second one the mordenite smaller channels. Brønsted acid sites in mordenites were active for the selective catalytic reduction of NO with CH₄. Co-MOR samples were far more active than Na-MOR and H-MOR samples, showing that acid protons play a negligible role when Co is present. Co-MOR catalysts showing the highest activity had the largest amount of Co^II-carbonyls in the main channels. This result strongly suggests that Co^II in the main channels of MOR are the active sites for the CH₄ + NO + O₂ reaction.     

Acrylonitrile/acrylamidoxime/2‐acrylamido‐2‐ methylpropane sulfonic acid‐based hydrogels: Synthesis,characterization and their application in the removal of heavy metals

Crosslinked acrylonitrile/acrylamidoxime/2‐acrylamido‐2‐methylpropane sulfonic acid (AN/AAx/AMPS)‐based hydrogels were prepared by free radical crosslinking solution polymerization technique. The chemical structures of the hydrogels were characterized by FT‐IR analysis. The morphology of the dry hydrogel sample was examined by scanning electron microscope (SEM). These hydrogels were used for the removal of Cd(II), Cu(II), and Fe(III) ions from their aqueous solutions. The influence of the uptake conditions such as pH, time and initial feed concentration on the metal ion binding capacity of hydrogel was also tested. The selectivity of the hydrogel towards the different metal ions tested was arranged in the order of Cd(II) > Fe(III) > Cu(II). It was observed that the specific interaction between metal ions and ionic comonomer in the hydrogel affected the metal binding capacity of the hydrogel. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Poly(l-lactic acid)/SiO2 nanocomposites via in situ melt polycondensation of l-lactic acid in the presence of acidic silica sol: Preparation and characterization

In situ melt polycondensation of l-lactic acid (LLA) in the presence of acidic silica sol (aSS) is proposed for the first time to prepare PLLA/SiO₂ nanocomposites. The SiO₂ nanoparticles were readily dispersed in LLA monomer, which has similar polarity and hydrophilicity to the silica sol medium. During the polycondensation process, both the matrix and the surface of SiO₂ nanoparticles changed from high polarity/hydrophilicity to weak polarity/hydrophobicity due to simultaneous chain growth in the organic phase and chemical grafting on the particle surface. The chemical grafting provided steric stabilization and ensured satisfactory nano-scale dispersion in the final nanocomposites. The introduction of SiO₂ nanoparticles resulted in unchanged yield and better color. The molecular weight kept almost constant at low SiO₂ content (<8 wt%) but decreased at higher SiO₂ content. The method is also characterized by commercially available and cheap starting material and environmentally benign process. It appears to be a promising approach for the preparation of PLLA/SiO₂ nanocomposites.