利用具有过水解活性的乙酰基木聚糖酯酶催化制备过氧乙酸

以甘油三乙酸酯和H2O2为底物,利用来源枯草芽孢杆菌的乙酰木聚糖酯酶(AXE)游离酶和固定化酶催化过水解反应制备过氧乙酸(PAA),并以化学法制备的过氧乙酸为对照组进行性质比较。结果表明:游离酶用量(酶蛋白)为1.0 g/L,可得到11.6 g/L的过氧乙酸,对甘油三乙酸酯的转化率为16.7%;游离酶用量(酶蛋白)为75 mg/L,过氧乙酸质量浓度可达3.5 g/L,对甘油三乙酸酯的转化率为15.3%;固定化酶用量(树脂量)为50 g/L,可得3.6 g/L的过氧乙酸。低浓度过氧乙酸比高浓度过氧乙酸更稳定。将对照组和酶法制备过氧乙酸的质量浓度均设置为3.5 g/L,其pH分别为1.98和4.45;对照组使铜片形成重度腐蚀,对碳钢有轻度腐蚀性,对不锈钢和铝基本无腐蚀;酶法制备的过氧乙酸对上述4种金属均无腐蚀。

植物根际芽胞杆菌菌种资源采集及其具有过水解催化活性水解酶基因的克隆

[背景]芽胞杆菌源枯草杆菌蛋白酶(subtilisin carlsberg)、乙酰基木聚糖酯酶(acetyl xylan esterase)和头孢菌素乙酰水解酶(cephalosporin acetyl hydrolase)具有较高的过水解催化活性,有商业开发价值。[目的]挖掘芽胞杆菌菌株中具有过水解酶催化活性的水解酶蛋白基因,为后续制备过水解酶及酶法合成过氧乙酸奠定基础。[方法]利用定向筛选培养基,从植物根际及纳豆产品中筛选产蛋白酶芽胞杆菌候选菌株,并利用RFLP及16S rRNA基因对其进行鉴定。从蛋白酶高产芽胞杆菌菌株中克隆枯草杆菌蛋白酶、乙酰木聚糖醋酶和头孢菌素乙酰水解酶的全长基因。[结果]从植物根际土壤及纳豆产品中共分离到85个候选菌株,RFLP及16S rRNA基因鉴定结果表明候选菌株均为芽胞杆菌,分别属于Bacillus subtilis、Bacillus cereus、Bacillus pumilus和Bacillus megaterium四个类群。从B.subtilis NSYT-3克隆的枯草杆菌蛋白酶基因编码的多肽链全长381个氨基酸,从B.pumilus OSLJ-3克隆得到的乙酰基木聚糖酯酶基因编码的多肽链全长320个氨基酸,从B.subtilis NSYT-3克隆的头孢菌素乙酰水解酶基因编码的多肽链全长318个氨基酸,3D结构模拟表明这3个酶蛋白均具有α/β水解酶折叠家族蛋白结构特点。[结论]芽胞杆菌源具过水解催化活性水解酶基因的克隆,为后续开发酶法合成过氧乙酸工艺奠定了基础。

在α-蒎烯生物环氧化反应过程中酯对反应的影响及机理探讨

在以过氧化脲(UHP)为氧源、Nov435为催化剂的体系中进行α-蒎烯生物环氧化反应的研究,重点考察不同酯作为酰基供体对反应的影响。从反应速率和酶批次稳定性综合考虑,以丙酸乙酯为最佳溶剂,30℃下α-蒎烯3h的环氧转化率可达到87%左右,经6批次反应后仍可达到47.6%,发现过酸和H2O2的协同作用对酶稳定性的影响要高于单一因素。酶催化乙酸乙酯、丙酸乙酯、乙酸戊酯、己酸乙酯等不同酰基供体过水解反应均可在60min达到平衡,但过酸平衡浓度和α-蒎烯化学环氧化反应速率受酯影响较大,进而对总反应化学-酶法联合催化环氧化产生影响。最后探讨了丙酸乙酯为唯一酰基供体时的反应机制,认为酶利用丙酸产过酸的反应速率和过酸平衡浓度远低于酯;丙酸乙酯的水解和过水解反应为一对竞争性反应,因此有机体系更有利于环氧化反应。

Influence of magnesium and aluminum salts on hydrolysis of titanyl sulfate solution

The influence of magnesium and aluminum salts as impurities on the hydrolysis of titanyl sulfate was investigated.The degree of TiOSO4 conversion to hydrated titanium dioxide（HTD） and the particle size of HTD were measured as functions of the concentrations of MgSO4 and Al2（SO4）3 in the TiOSO4 solution.The Boltzmann growth model,which focuses on two main parameters,namely the concentrations of Mg2＋ and Al3＋（ρ（Mg2＋） and ρ（Al3＋）,respectively）,fits the data from the hydrolysis process well with R20.988.The samples were characterized by ICP,SEM,XRD,and laser particle size analyzer.It is found that the addition of Mg SO4 simultaneously improves the hydrolysis ratio and the hydrolysis rate,especially when F（the mass ratio of H2SO4 to TiO2） is high,hydrolysis ratio increases from 42.8% to 83.0%,whereas the addition of Al2（SO4）3 has negligible effect on the chemical kinetics of HTD precipitation during the hydrolysis process,hydrolysis ratio increases from 42.8% to 51.9%.An investigation on the particle size of HTD reveals that the addition of Mg SO4 and Al2（SO4）3 clearly increases the size of the crystallites and decreases the size of the aggregates.

THE PREPARATION OF PEROVSKITE TYPE STRONTIUM TITANATE BY SOL-GEL PROCESS

By using strontium acetate and titanium n--butoxide [Ti(OBun)4] as starting agents, perovskite -- type double oxide SrTiO3 can be obtained by the sol--gel method. By means of infra-red spectra (IR), X--ray diffraction (XRD), differential thermal analysis (DTG), thermal gravimetry (TG) and scanning electron microscopy (SEM), basical factors, affecting the formation .of SrTiO3,have been discussed. IR results show that the acetic acid as a chelating ligand plays an important role in modifying the whole hydrolysis --condensation process. The addition of glycerol leads to obtaining clear and unique gels. The structure of SrTiO3 calcined at 800℃ is cubic.

In situ growth of minimal Ir-incorporated CoxNi1-xO nanowire arrays on Ni foam with improved electrocatalytic activity for overall water splitting

Exploration of cost-effective electrocatalysts for boosting the overall water-splitting efficiency is vitally important for obtaining renewable fuels such as hydrogen.Here,earth-abundant CoxNi1-xO nanowire arrays were used as a structural framework to dilute Ir incorporation for fabricating electrocatalysts for water splitting.Minimal Ir-incorporated CoxNi1-xO nanowire arrays were synthesized through the facile hydrothermal method with subsequent calcination by using Ni foam(NF)as both the substrate and source of Ni.The electrocatalytic water-splitting performance was found to crucially depend on the Ir content of the parent CoxNi1-xO nanowire arrays.As a result,for a minimal Ir content,as low as 0.57 wt%,the obtained Ir-CoxNi1-xO/NF electrodes exhibited optimal catalytic activity in terms of a low overpotential of 260 mV for the oxygen evolution reaction and 53 mV for the hydrogen evolution reaction at 10 mA cm?2 in 1 mol L–1 KOH.When used as bifunctional electrodes in water splitting,the current density of 10 mA cm–2 was obtained at a low cell voltage of 1.55 V.Density functional theory calculations revealed that the Ir-doped CoxNi1-xO arrays exhibited enhanced electrical conductivity and low Gibbs free energy,which contributed to the improved electrocatalytic activity.The present study presents a new strategy for the development of transition metal oxide electrocatalysts with low levels of Ir incorporation for efficient water splitting.

Effects of H_3PO_4 and Ca(H_2PO_4)_2 on mechanical properties and water resistance of thermally decomposed magnesium oxychloride cement

The effects of H3PO4 and Ca（H2PO4）2 on compressive strength, water resistance, hydration process of thermally decomposed magnesium oxychloride cement （TDMOC） pastes were studied. The mineral composition, hydration products and hydration heat release were analyzed by XRD, FT-IR, SEM and TAM air isothermal calorimeter, etc. After being modified by H3PO4 and Ca（HzPO4）2, the properties of the TDMOC are improved obviously. The compressive strength increases from 14.8 MPa to 48.1 MPa and 37.1 MPa, respectively. The strength retention coefficient （Kn） increases from 0.38 to 0.99 and 0.94, respectively. The 24 h hydration heat release decreases by 10% and 4% and the time of hydration peak appearing is delayed from 1 h to about 10 h. The XRD, FT-IR and SEM results show that the main composition is 5Mg（OH）z＇MgCIz＇8H20 in the modified TDMOC pastes. The possible mechanism for the strength enhancement was discussed. The purposes are to extend the potential applications of the salt lake magnesium resources and to improve the mechanical properties of TDMOC.

Simultaneous hydrogen and peroxide production by photocatalytic water splitting

Photocatalytic oxidation of water is a promising method to realize large-scale H2O2 production without a hazardous and energy-intensive process. In this study, we introduce a Pt/TiO2(anatase) photocatalyst to construct a simple and environmentally friendly system to achieve simultaneous H2 and H2O2 production. Both H2 and H2O2 are high-value chemicals, and their separation is automatic. Even without the assistance of a sacrificial agent, the system can reach an efficiency of 7410 and 5096 μmol g^-1 h^–1 (first 1 h) for H2 and H2O2, respectively, which is much higher than that of a commercial Pt/TiO2(anatase) system that has a similar morphology. This exceptional activity is attributed to the more favorable two-electron oxidation of water to H2O2, compared with the four-electron oxidation of water to O2.

Preparation of hexagonal and amorphous chromium oxyhydroxides by facile hydrolysis of K_xCrO_y

The hydrolysis process and mechanisms of unique as-prepared KCrO2 and K3 CrO4 were systematically investigated. The characterization results of XRD, IR and SEM show that the hydrolysis reaction can be realized at a low reaction temperature of 80 ℃ and a reaction time of 24 h. Moreover, the greyish-green α-CrOOH with a hexagonal plate-like morphology and a large size of 10 μm is formed via the hydrolysis of the single-phase hexagonal KCrO2, while the green sol-gel of amorphous Cr(OH)3 with a lumpy aggregate morphology is generated through the hydrolysis of a cubic K3 CrO4. It is a facile and rapid method to synthesize pure-phase chromium oxyhydroxide via the above hydrolysis.

Resistivity in Formation and Decomposition of Natural Gas Hydrate in Porous Medium

A new one-dimensional system for resistivity measurement for natural gas hydrate(NGH)exploitation is designed,which is used to study the formation and decomposition processes of NGH.The experimental results verify the feasibility of the measurement method,especially in monitoring the nucleation and growth of the NGH. Isovolumetric formation experiment of NGH is performed at 2°C and 7.8 MPa.Before the NGH formation,the initial resistivity is measured to be 4-7Ω·m,which declines to the minimum value of 2-3Ω·m when NGH begins to nucleate after the pressure is reduced to 3.3 MPa.As the NGH grows,the resistivity increases to a great extent,and finally it keeps at 11-13Ω·m,indicating the completion of the formation process.The NGH decomposition experiment is then performed.When the outlet pressure decreases,NGH begins to decompose,accordingly,the resistivity declines gradually,and is at 5-9Ω·m when the decomposition process ends,which is slightly higher than the resistivity value before the formation of NGH.The occurrence and distribution uniformity of NGH are determined by the distribution and magnitude of the resistivity measured on an one-dimensional sand-packed model.This study tackles the accurate estimation for the distribution of NGH in porous medium,and provides an experimental basis for further study on NGH exploitation in the future.

Kinetic Studies on Wheat Straw Hydrolysis to Levulinic Acid

Levulinic acid is considered as a promising green platform chemical derived from biomass.The kinetics of levulinic acid accumulation in the hydrolysis process of wheat straw was investigated in the study.Using dilute sulfuric acid as a catalyst,the kinetic experiments were performed in a temperature range of 190-230°C and an acid concentration range of 1%-5% (by mass) .A simple model of first-order series reactions was developed,which provided a satisfactory interpretation of the experimental results.The kinetics of main intermediates including sugar and 5-hydroxymethylfurfural(5-HMF) were also established.The kinetic parameters provided useful information for understanding the hydrolysis process.

Effect of Increasing Course of Temperature and Pressure on Polypropylene Degradation in Supercritical Water

The effect of increasing course of temperature and pressure on polypropylene （PP） degradation in supercritical water was investigated for developing a process of recycling waste plastic. A group of experiments was carded out in a reaction system at a pressure of 26MPa, temperature of 380℃ or 400℃ for 30min, 70min, and 120min by Course One （the increasing course of temperature and pressure is via gaseous regions to supercritical regions）, and the other group was carried out at corresponding holding conditions by Course Two （the increasing course of temperature and pressure is via liquid regions to supercritical regions）. The time of the increasing courses was about 30min. Products were analyzed by Ostward-type viscometer, gaseous chromatography, and mass spectrometers （GC/MS）. Characterization results suggested that different increasing courses of temperature and pressure would give rise to different results, although they were treated under the similar holding conditions. It was also found that Course Two was more effective on PP degradation in supercritical water.

Improvement of Cellulose Hydrolysis Process and Cost Savings

The hydrolysis process to obtain the so-called ＂reducing sugars＂ represents the main step involved in the production of the second generation bioethanol. This product can be obtained directly from various types of green biomass, replacing the use of cereals cultivations, with obvious benefits to the environment and the economy of agricultural production. However, it is necessary to improve the hydrolysis process of the cellulose to achieve this goal. To this purpose, we applied a chemical process formerly used. The values of sugars yield were increased by about 40% with respect to the previous study. Further significant cost savings were accomplished, resulting from the recovery of the by-product, calcium sulfate, commercially known as gypsum.

Kinetic Parameter of Alfa-amylase and Glucoamylase Enzymatic Reaction on the Glucose Yield from Hydrolyzed Processes of Tapioca Solid Waste

The increasing of tapioca production nowadays effected the production of waste. The waste of tapioca industries consists of two kinds, which were liquid waste and solid waste. Further more, tapioca solid waste treatment was ineffective. Weather solid waste produced from the extraction process still contains high concentration of starch that can be used to produce high quality product, for example, bio ethanol or other alternative energy sources. Objective of these experimental work was utilizing solid waste of tapioca industries and looking for the exactly composition of n-amylase and gluco-amylase enzymes on the hydrolysis processes of the solid waste of tapioca. The exact composition from both enzymes can be expected to increase the yield of glucose. Variables of cx-amylase enzyme for this research were 0.3% （w/w） and 0.5% （w/w） with liquefaction time were 1 hour and 1.5 hours, and variables of glucoamylase enzyme were 0.3% （w/w） and 0.5% （w/w）. To achieve these goals, the experimental work was held in laboratory scale with batch process. Firstly, tapioca solid waste was pretreated at 90 ~C and added u-amylase enzyme for 1 hour and 1.5 hours （variable of liquefaction time）. Then, substrate was cooled down to 60 ~C added with proposed variables of glucoamylase enzyme, and was analysed 24 hours after added. This experiment showed the best ratio between a-amylase and glucoamylase enzymes 0.5%：0.5% with 1 hour of liquefaction time. The highest glucose reaches 8.468% and yields 0.892 （g glucose/g starch） with starch conversion of 59.94%. KM = 0.0468 g/mL and rmax = 0.311 g/mL·h,

Experimental study of water effects on gas desorption during highpressure water injection

For the question of applying high-pressure water injection to increase gas extraction efficiency by increasing the permeability of water to drive gas action, an independently designed gas desorption experimental measuring device was used under the condition of external solution invasion. The law of water effect on gas desorption was obtained after water invasion through experiment for the first time. The results show that water＇s later invasion not only can make the quantity of gas dcsorp- tion greatly reduced, but also can make gas desorption end early. Therefore, when evaluating the applications of high-pressure water injection to increase gas extraction efficiency, we should take water damaging effects on gas desorption into account.

Hydrolysis of Lactose： Estimation of Kinetic Parameters Using Artificial Neural Networks

The analysis of any kinetic process involves the development of a mathematical model with predictive purposes. Generally, those models have characteristic parameters that should be estimated experimentally. A typical example is Michaelis-Menten model for enzymatic hydrolysis. Even though conventional kinetic models are very useful, they are only valid under certain experimental conditions. Besides, frequently large standard errors of estimated parameters are found due to the error of experimental determinations and/or insufficient number of assays. In this work, we developed an artificial neural network （ANN） to predict the performance of enzyme reactors at various operational conditions. The net was trained with experimental data obtained under different hydrolysis conditions of lactose solutions or cheese whey and different initial concentrations of enzymes or substrates. In all the experiments, commercial 13-galactosidase either free or immobilized in a chitosan support was used. The neural network developed in this study had an average absolute relative error of less than 5% even using few experimental data, which suggests that this tool provides an accurate prediction method for lactose hydrolysis.

Research on the Influence of Acid Concentration on Reducing Sugar in Straw Waste

This paper studies the effect of reducing sugar concentration, reducing sugar yield and byproducts furfural concentration that generate by straw under the condition of acid concentration and flow rate in the gradient temperature hydrolysis process （60℃-230℃）, we can conclude that reducing sugar yield is highest when the concentration of sulfuric acid is 1%, the velocity of reaction liquid is 25mL/min, at the highest concentration of wheat straw yield of reducing sugar up to 32.9g/L, the reducing sugar yield was 60.8%. At this point the furfural concentration is lower than 1.0g/L, but in the entire gradient heating process, reducing sugar concentration peak of furfural concentration peak appears in the temperature lower, can realize the separation of the reducing sugar and furfural good, reduce the inhibition of fermentation by- products such follow-up treatment process.

Biological activities of a neutral water-soluble agar polysaccharide prepared by agarase degradation

Depolymerization of agar was performed using agarase, which was extracted from the cell-free medium of a culture of marine bacterial Alterornonas sp. nov. SY 37-12. After ethanol fractionation and lyophilization, the water-soluble agar polysaccharide （WSAP3） was collected. The anti-tumor activity of the product was determined by using Sarcoma 180 tumor in mouse. The tumor inhibition rate of WSAP3 the product was determined by using Sarcoma 180 tumor in mouse. The tumor inhibition rate of WSAP3 reached 48.7% at a dose of 64mg kg^-1 after 15 days treatment. WSAP3 enhanced the aetivities of superoxide dismutase and catalase, which suggests that WSAP3 was effective in promoting the antioxidation ability and eliminating danger from free radicals. The result of flow cytometry showed that the WSAP3 had no activities of cell cycle inhibition or apoptosis-inducing activities. The anti-oxidation of WSAP3 was further confirmed by test in vitro, which might play an important role in anti-tumor activity. The immunological regulation of WSAP3, especially its effect on the phagocytosis ratio and phagocytosis index of rophage was also assayed in test in vivo.

Combinatorial model of solute transport in porous media

Modeling of solute transport is a key issue in the area of soil physics and hydrogeology. The most common approach (the convection-dispersion equation) considers an average convection flow rate and Fickian-like dispersion. Here,we propose a solute transport model in porous media of continuously expanding scale, according to the combinatorics principle. The model supposed actual porous media as a combinative body of many basic segments. First, we studied the solute transport process in each basic segment body, and then deduced the distribution of pore velocity in each basic segment body by difference approximation, finally assembled the solute transport process of each basic segment body into one of the combinative body. The simulation result coincided with the solute transport process observed in test. The model provides useful insight into the solute transport process of the non-Fickian dispersion in continuously expanding scale.

Research on soil salt transfer under freeze-thawing condition

Soil salt transformation plays an important role in the freeze-thawing process,which is also one of basic problems of cryopedology. The very special law is made up of the two time salt-moisture transfer under freeze-thawing condition. Based on the latest research at home and abroad,through the investigation of soil moisture-salt change in the freeze-thawing process,the conclusion is made that the soil water potential gradient is the main driving force of soil salt movement and the factors are of quantities. The research shows that,when freezing,temperature drops,salt and moisture move towards frozen layer. All make the salinity content of the frozen layer increase significantly. In the thawing process,salinity and moisture in the soil move up again with evaporation and makes the salt second migration.