The preparation of an immobilised glucose isomerase. I. The production and selected properties of the partially-purified enzyme from Lactobacillus brevis

A strain of Lactobacillus brevis producing glucose isomerase was grown in a xylose-containing medium. Production of intracellular glucose isomerase was four times that previously reported. Methods for the release of enzyme were compared, and a process for the production of an enzyme concentrate proposed involving (i) heat autolysis of the cells at 40 °C for 8 h; (ii) precipitation of nucleic acids with manganese chloride; (iii) precipitation of enzyme with ammonium sulphate, collecting the fraction precipitated between 60 and 85% saturation, and (iv) heat treatment of the dissolved enzyme at 55 °C in the presence of Co²⁺ for 10 min. Enzyme concentrates prepared using steps (i) to (iii) only showed considerable competing activity, and produced sigmoid kinetics. The use of enzymes prepared using the full method showed that substrate inhibition was apparent at glucose concentrations above approximately 30% w/v. The apparent K_M value was calculated as 10 to 12% w/v (glucose), based on the definition of K_M as K_M= S_o at V_o - V_max(observed)/2. The equilibrium concentrations of fructose and glucose were 62 and 38% respectively, and were independent of temperature between 35 and 60 °C.     

A theoretical analysis of the deactivation of an immobilised enzyme in multi-enzyme reactions in fixed-bed and fluid-bed reactors

The effect of time-averaging on the selectivity to an intermediate R (yR ) and the yield to product S (yR ) in a consecutive reaction A→R→S, occurring in a deactivating fixed-bed reactor, has been examined. Time-averaging smooths the selectivity and increases the yield for high values of the deactivation (λ) and reaction (δ) parameters. The kinetics and dynamics of yR and yS in a deactivating steady-state fluid-bed reactor were also examined. Both non-selective and selective deactivation are considered. The practical implications of the development are considered in terms of an example, in which the values chosen for parameters are arbitrary though reasonable with respect to experimental values.     

The preparation and properties of acrylic and methacrylic acid grafted cellulose prepared by ceric ion initiation. II. Water retention properties

Bleached sulfite softwood pulp and the corresponding paper have been grafted with acrylic and methacrylic acids and a number of other monomers. A practical, all aqueous, ceric ion method was used as described in Part I of this series. The water and saline retention values of the grafted pulps were determined. Super water sorbency, up to 48 g/g, were obtained after suitable post treatments. A number of variables were studied including the effects of pH, counterion, crosslinking, drying, and beating. It was gratifying that drying did not affect the effeciency of water or saline water retention. Useful linear functional relationships were found between the saline water retention values and the logarithm of the percent sodium chloride in the water. The two “model” parameters of the plots also correlated well with the water retention values and with the degree of grafting expressed as the ion exchange equivalents of the pulps. The osmotic pressure approach to the water sorption as developed by Grignon and Scallan⁵ coupled with the restraining forces of the grafted polymer itself is used to interpret the process.     

Porous bead polyaromatic copolymers containing ester groups. II. The influence of the preparation conditions on surface properties of copolymers

Porous bead copolymers of styrene with 4,4′-di(methacryloyloxymethyl)diphenylmethane (DMD) have been prepared. Preparation conditions (composition of the monomer mixture with an inert component) were discussed with respect to the porous properties of copolymers (the specific surface area, pore size distribution and mean pore radius).     

氯代纤维素的制备及其性质的研究

本文用氯化锂／二甲基乙酰胺（LiCl/DMAc）作溶剂在均相条件下制备了氯代纤维素，研究了影响氯代反应速率的若干因素，讨论了产品的若干性质。研究发现，在氯代反应过程中存在两种取代反应，一个是氯原子取代，另一个是乙酰基取代。取代基的位置主要集中在葡萄糖基的第六位碳原子（C_6）上。纯的氯代纤维素仅溶解在DMAc中，而带有少量乙酰基的氯代纤维素则可以溶解在甲醇、乙醇、丙酮以及DMAc等溶剂中。在氯代纤维素的DSC曲线上有两个峰，一个是吸热峰，而另一个是放热峰。     

紫外光固化胶粘剂的制备及性能研究

以丙酮为溶剂、AIBN(偶氮二异丁腈)为热引发剂和NDM(十二烷基硫醇)为链转移剂,采用半连续加料工艺制备出黏度适宜的丙烯酸酯预聚体;然后以此为基体、184(1-羟基环己基苯基甲酮)为自由基光引发剂、IBOA(丙烯酸异冰片酯)和TPGDA(二缩三丙二醇二丙烯酸酯)为活性稀释剂,配制出性能优异的UV(紫外光)固化胶粘剂。研究结果表明:当w(AIBN)=1.0%(相对于单体总质量而言)、w(NDM)=1.5%和w(丙酮)=30%(均相对于UV固化胶粘剂总质量而言)以及聚合温度为75℃时,能够合成出黏度为10 Pa·s的丙烯酸酯预聚体;当w(活性稀释剂)=40%(相对于UV固化胶粘剂总质量而言)、m(IBOA)∶m(TPGDA)=10∶30时,UV固化胶膜的折射率达到了1.50左右,透光率在一定波长范围内超过了90%。     

Photo-electro-chemical properties of TiO2 mediated by the enzyme glucose oxidase

Electrochemical measurements show that the enzyme glucose oxidase (GO) is adsorbed on the surface of TiO₂ without apparently changing the flat band potential of the semiconductor, indicating that it does not cause a change of the energy of conduction band electrons. On the other hand, it is observed that GO markedly increases the efficiency of the two electron reduction of O₂ to H₂O₂ which is accumulated in the solution phase.

ESR spin trapping investigations indicate that GO favors the formation of OH radicals, due to either the inhibition of charge recombination processes or to H₂O₂ reduction by conduction band electrons. Accordingly, photo-oxidation of different alcohols to the corresponding radical species is also enhanced in the presence of GO.

The photo-oxidation of 1,2-propandiol on TiO₂/GO is regioselective in that (i) partial oxidation to hydroxyacetone is observed and (ii) no mineralization (full combustion to CO₂) of the substrate occurs. These facts are of particular interest in the field of studies concerning the design of new photocatalytic systems with enhanced activity and controllable oxidative power.     

Influence of the preparation conditions on the properties of gold catalysts for the oxidation of glucose

In this work, two deposition–precipitation methods for the preparation of gold catalysts for glucose oxidation were investigated. Thus far, gold colloids immobilized on carbon have been used for catalytic glucose oxidation, but the long-term stability of these systems was not sufficient. To improve the long-term stability we used the deposition–precipitation methods using NaOH (DP NaOH) or urea (DP urea) as precipitation agents as they were described by Haruta and Dekkers, respectively, using alumina as a support material. With these methods, it was possible to prepare highly active and selective catalysts which showed an excellent long-term stability. DP urea was found to be the preferred method, because in contrast to DP NaOH, no losses of gold occurred during the preparation, and it was possible to adjust various gold contents up to 10 wt% Au.     

Pore network model of deactivation of immobilized glucose isomerase in packed-bed reactors II: three-dimensional simulation at the particle level

Immobilized glucose isomerase is widely used for converting glucose to fructose by enzymatic isomerization. The process takes place in a packed-bed reactor consisting of mesoporous particles with distributed pore sizes and interconnectivities. Its efficiency is, however, significantly affected by deactivation of the mesoporous particles. In this paper, we study deactivation of the mesoporous particles using a three-dimensional pore network model of the pore space with distributed pore sizes and interconnectivities, and investigate several plausible mechanisms of deactivation of the porous particles. The results of the present study, which will be used as the input for simulation of the phenomenon at the reactor level, demonstrates the strong effect of the particles’ morphology on the deactivation process.     

Comparison of backbone structures of glucose isomerase from Streptomyces and Arthrobacter

The C backbones of the glucose isomerase molecules of Streptomycesrubiginosus and Arthrobacter have been determined by X-ray crystallographyand compared. Each molecule is a tetramer of eight-stranded/ß barrels, and the mode of association of the tetramersis identical in each case. The Arthrobacter electron densityshows four additional amino acids at the carboxyl terminus.There is also an insertion of six amino acids at position 277,and two individual insertions at about positions 348 and 357(numbering according to the Streptomyces structure). There isa close structural homology throughout the whole molecule, whichis most accurate up to position 325. The r.m.s. displacementfor 315 homologous C positions up to this position is 0.92 Å.     

ITO膜的制备及性能研究

采用直流磁控溅射技术,在玻璃上沉积了30 nm～700 nm厚的系列透明导电ITO(In_2O_3∶Sn)薄膜。研究膜厚对透光率、方阻和屏效的影响。可见光的平均透光率在79%～87%,方阻在1.4Ω/～44Ω/之间变化,在低频的时候,屏蔽效能和膜厚没有多大的关系,在高频阶段屏蔽效能随膜厚的增加而增大。     

琥珀酰基月桂酰壳聚糖的制备及性能

以丁二酸酐和壳聚糖(CS)为原料合成亲水性琥珀酰基壳聚糖(SCS),然后与月桂酰氯通过酰化反应制备了两亲性的琥珀酰基月桂酰壳聚糖(LSCS)。采用FTIR和1HNMR对壳聚糖衍生物进行了结构表征。LSCS的琥珀酰基的取代度为41.27%,月桂酰基的取代度为6.32%。改性后的壳聚糖在pH<3.0和pH>6.5时溶解度较好,在等电点及附近的pH范围内溶解度降低。LSCS具有较强的分子间相互作用,随其质量分数增加溶液黏度显著增加,且在质量分数达到2%时可形成物理凝胶。该物理凝胶对NaCl浓度较敏感,随着NaCl浓度的增加,凝胶强度减小。     

The preparation and properties of surface-active N-acylamino-methanesulfonates

Summary The preparation and properties of aminomethanesulfonic acid and several of its lower and higher N-alkyl derivatives have been studied. The acylation of these compounds was investigated, and the optimum conditions were determined. Measurements of the surface-active properties, including pour foam, soil removal, and redeposition, of several of the acylated derivatives are described, with reference to Igepon T.     

The preparation and properties of vinyl cellulose

The vinylation of cellulose by acetylene under alkaline conditions was optimized with respect to both DS and DP. Shortening the reaction time reduced the harmful alkaline depolymerization of cellulose during the reaction and gave products with higher DP values. Thus cellulose, activated by KOH, was vinylated for 180 min at 431K and 5.5 MPa to yield 72.1% of a product with DS 1.46 and DP _w 175. Results of vinyl cellulose analysis by new and old methods were in good agreement with each other. Trimethylsilylated vinyl cellulose was prepared for proton NMR and GPC measurements. It was found that vinyl cellulose slowly loses its vinyl groups when stored in light and air.     

The preparation of alkyl esters from highly unsaturated triglycerides. II

A previously described procedure for the basecatalyzed alcoholysis of fish-oil triglycerides with alcohols of low molecular weight has been applied to the preparation of alkyl esters using high molecular weight, aromatic, and terminally unsaturated alcohols. Some monoethers of ethylene-and diethylene glycol have also been used in this work. Thin-layer chromatography was used to follow the course of the reaction and determine optimum reaction times and yields of products.     

一种UV固化聚硫代醚密封胶的制备与性能研究

利用巯基-乙烯基"点击"反应制备了一种UV(紫外光)固化聚硫代醚密封胶。探讨了引发剂、填料等对UV固化聚硫代醚密封胶的固化深度、拉伸性能和粘接性能等影响。研究结果表明:与室温固化聚硫代醚密封胶相比,UV固化聚硫代醚密封胶具有固化速率较快、固化过程几乎不受环境影响等优势;UV固化聚硫代醚密封胶的力学性能良好,具有稳定的粘接性能,并且其耐高温性能比聚硫密封胶更优异。     

The effect of glucose oxidase enzyme on wool fibres

Glucose oxidase is a type of enzyme that converts glucose into hydrogen peroxide and gluconic acid by enzymatic reaction. Glucose oxidase is widely used in industry; however, in the textile industry, glucose oxidase has only received academic interest. Previously, wool was bleached by some reducing agents; however, currently in industry, hydrogen peroxide dominates the bleaching of wool fibres. In this study, the effect of glucose oxidase enzyme treatment on wool merino fibres and dyeability properties was investigated. Wool fibres were treated with glucose oxidase enzyme, after which the whiteness index (Stensby) and yellowness index (ASTM D 1925 and ASTM E 313) were investigated. Scanning electron microscopy and scanning electron microscopy with energy dispersive X-ray spectroscopy were used to identify the morphological structure of wool fibres and their atomic content. The chemical damage caused by enzyme was investigated using a fluorescence and a light microscope, and the alkali solubility (ASTM D 1283) was determined. After enzymatic treatment, the wool fibres were dyed at a 2.0% concentration with reactive dyes. Dyeability (K/S) and CIELab values were assessed with a Minolta CM 3600 D spectrophotometer (D65, 10°). The washing fastness of wool fibres was investigated according to TS EN ISO 105-C06 (A1S).     

The rotating electrolyser. II. Transport properties and design equations

It is shown that mass transfer in the rotating electrolyser is controlled by the rotational Reynolds number (Re _φ) and that species electrogenerated at the wall are confined to a thin layer close to the wall. The radial dispersion coefficient is of the same order as that of a non-rotational, capillary gap cell. Criteria for scale-up are discussed briefly.     

明胶的酶降解反应动力学研究——Ⅱ.动力学规律和机理

根据文献[1]中的实验数据,结合化学反应动力学的基础理论,计算了明胶的酶降解反应的反应级数、表观活化能、指前因子等有关动力学参数值。得到反应的总速率方程。所求得的反应速率常数与温度的关系表明,在实验温度范围内,符合Arrhenius公式。最后提出了该反应的酶催化反应机理,实验结果与所推得的机理动力学方程相吻合。