一株丝状真菌对半纤维素利用的初步研究

本文筛选出一株能利用木糖产乙醇的丝状真菌Z7，对其利用木糖和半纤维素水解产物产乙醇的发酵条件进行了研究，并对Z7 利用玉米芯产木聚糖酶的条件进行了优化。全文分为三部分： 第一部分：目标微生物筛选、纯化及系统发育分析。以木糖为唯一碳源，采用梯度稀释和平板化线法从高温、中温酒曲中分离到16 株能利用木糖良好生长的丝状真菌；通过发酵试验复筛，获得一株能产乙醇的丝状真菌Z7；综合形态学和ITS 序列分析，初步鉴定为Aspergillus flavus。 第二部分：Z7 的乙醇发酵条件研究。以木糖为碳源，通过单因素试验确定最佳氮源和发酵温度；通过正交试验及SPSS 软件分析得到了不同N、P、K 成分对乙醇、残糖和菌体干重的影响。获得最佳的发酵条件为：（g/L）木糖50，尿素1, NH4NO3 1, K2HPO4 2 , KCl 0.5 , MgSO4.7H2O 0.5 , NaNO3 1 , pH 自然，培养温度33 ℃。以玉米芯半纤维素稀酸水解液为底物进行乙醇发酵，根据稀酸水解的单糖释放量和乙醇产量，确定115 ℃，1 h 为最佳玉米芯预处理条件；结合最佳发酵条件，添加1 g/L 的吐温20 能获得最大的乙醇浓度8.31 g/L。因此，Aspergillus flavus Z7 能利用半纤维素水解产物产乙醇，其中木糖的利用率80%以上。 第三部分：Z7 利用玉米芯产木聚糖酶条件优化。Aspergillus flavus Z7 在具有产乙醇能力的同时还具有产木聚糖酶的能力。本文通过单因素和正交试验得到最佳产酶培养基组分为：(g/L)玉米芯20，尿素2, 酵母膏2.5, K2HPO4 5，NaNO31, MgSO4.7H2O 1。单因素试验表明，用纱布代替塑料布密封摇瓶封口能显著提高产酶量；Z7 在碱性条件下具有更强的产酶性能。在最优条件下发酵，能产生最大木聚糖酶活122.23IU/mL。通过薄层分析，验证了Z7 产生的木聚糖酶具有水解木聚糖生成木糖及木寡糖的能力。 A strain of filamentous fungus which can produce ethanol by using the xylose was isolated in this research. The ethanol fermention conditions from xylose and dilute-acid hydrolyzate of the corn core were studied. The conditions of xylanase production by Z7 were also optimized. The paper involved three parts. Part1: Isolation, purification and phylogenetic analysis of the microbe. By using xylose as the single carbon source and the pla te streaking method, several filamentous fungi were isolated from the wine starter; through the fermentation test, a filamentous fungus Z7 which can produce ethanol was further recognized; furthermore, according to the morphologic observation and ITS seque nces analysis, Z7 was identified as Aspergillus flavus at the first step. Part2: Research on the condition of ethanol fermentation by Z7. By single factor experiment, the optional nitrogen resource and temperature of the fermentation were fixed; meanwhile, through the orthogonal array tests and the analysis of statistic software SPSS, the optional component of the culture medium and the fermentation condition were organized as follows: (g/L) xylose 50, urea 1, NH4NO3 1, K2HPO4 2, KCl 0.5 , MgSO4.7H2O 0.5, NaNO31, pH nature, temperature 33℃. Based on these optimal parameters, the fermentation of dilute-acid hydrolyzate of the corn core was carried on by Z7. According to the quantities of released sugar monomers and content of the ethanol, 115℃ in 1h is the best pretreatment condition; the maximal ethanol content can be obtained when 1g/L Tween 20 was added to. Therefore, the filamentous fungus Aspergillus flavus can use the hydrolysate of hemicellulose to produce ethanol, and the rate of xylose utilization was over 80%. Part3: Optimization of Z7’s xylanase producing condition from corn core. Aspergillus flavus Z7, which can utilize xylose or the hydrolysate of hemicellulose to produce ethanol, also had the ability of xylanase production. The optional component of the culture medium were fixed by the single factor experiment and the orthogonal array tests, and they were organized as follows: (g/L) corn core 20, Urea 2, Yeast extract 2.5, K2HPO4 5, NaNO31, MgSO4.7H2O 1; it was testified by the single factor experiment that sealing the shaking flasks with pledget other than plastic paper can obviously increase the xylanase activity; moreover, Z7 showed better xylanase production ability when in the alkali environment. Under the optional fermentation condition, the maximal xylanase activity 122.23IU/mL was proved. Through the analysis of thin- layer chromatography (TLC), the ability of xylanase from Z7, which can hydrolyze xylan to xylose monomer and oligomer, was vividly displayed.

Synthesis of substituted pyridyl ureas by selenium dioxide-catalyzed carbonylation

A series of commercially useful substituted pyridyl ureas have been synthesized via selenium dioxide-catalyzed reductive carbortylation of substituted nitrobenzene or substituted nitropyridine with amine as co-reagent and carbon monoxide as carbonyl reagent instead of phosgene in one-pot reaction. The recycling reusability of catalyst was also tested. It was also found that selenium dioxide-catalyzed reductive carbonylation of nitroaromatics exhibited reaction-controlled phase-transfer phenomena of the catalyst. (C) 2003 Elsevier B.V. All rights reserved.

EA-IRMS法测定不同类型土壤有机碳稳定性同位素组成

利用元素分析仪-稳定同位素比例质谱仪(EA-IRMS)分析系统,以国际标准物质Urea为基准,标定了高纯钢瓶CO2参考气,其δ13CvsPDB值为(-29.523±0.181)‰。通过试验对比检验了EA-IRMS分析系统的稳定性、线性,测定δ13C值的样品分析精度,建立了测定土壤中有机碳稳定性同位素的分析方法。其离子强度在1.0~7.0V之间具有良好的线性,在1.5~5.0V内的线性优于总体线性;样品分析精度优于0.15‰;样品含碳量大于5μg即可满足测定δ13C的分析要求。应用此方法实测了18份不同类型土壤的有机碳稳定同位素组成,获得其13C天然丰度平均值为1.082%;不同类型的土壤有机碳稳定同位素组成存在较大的差异。

Thermodynamic studies of monuron

Monuron (C9H11ClN2O; N,N-dimethyl-N'-(4-chlorophenyl) urea, CAS 150-68-5) was synthesized and the heat capacities of the compound were measured in the temperature range from 79 to 385 K with a high precision automated adiabatic calorimeter. No phase transition or thermal anomaly was observed in this range. The enthalpy and entropy data of the compound relative to the reference temperature 298.15 K were derived based on the heat capacity data. The thermodynamic properties of the compound were further investigated through DSC and TG analysis. The melting point, the molar enthalpy, and entropy of fusion were determined to be 447.6 +/- 0.1 K, 29.3 +/- 0.2 kJ mol(-1), and 65.4 J K-1 mol(-1), respectively. (C) 2004 Elsevier B.V. All rights reserved.

Detection of K-ras exon 1 mutations by constant denaturant capillary electrophoresis

Among various mutation detection methods, constant denaturant capillary electrophoresis (CDCE) is one of the most common techniques for rapid identification of known or unknown mutations. In this report, a CDCE analysis method with homemade linear polyacrylamide (LPA) kit was developed on ABI 310 genetic analyzer, the effect and relationship of various denaturing factors in CDCE analysis were investigated and K-ras gene mutations of 31 coloerctal cancer patients were detected. Results indicate that, with the increase of chemical danaturant concentration, the optimum temperature was lowered, and when the concentration of urea (formamide) was higher than 7 M (40%), the homoduplex and heteroduplex of mutant samples were separated with difficulty. Detection results of K-ras gene in colorectal samples indicated that mutations were present in eight (26%) of 31 patients; most mutations were localized in codon 12, which is thought to be a critical step and plays an important role in human colorectal carcinogenesisas. Copyright (C) 2004 John Wiley Sons, Ltd.

小麦根系对水分和氮肥的生理生态反应

利用模拟土柱研究了不同水分和氮素营养条件下春小麦根系的生理生态反应。结果表明 ,适量施氮 (尿素 60 0kg/hm2 )增加了总根重和深层土壤中的根重 ,改善了根系的水分关系 ,提高了细胞膜的稳定性 ,因而有助于提高小麦的抗旱性 ;过量施氮 (尿素 150 0kg/hm2 )增加上层根重对抗旱性的意义并不大。严重水分胁迫下 ,过量施氮导致根细胞膜伤害率明显增加 ,根系水分关系恶化 ,根系保水能力下降 ,使小麦抗旱性降低

施用农用化学品及生防制剂对土壤线虫群落动态影响的研究

Dynamics of soil nematode communities amended with agrochemicals and bio control preparations were investigated in a soybean field. The results showed that the frequency of plant non parasitic nematodes were obviously higher in soil amended with bio control preparations (Doufeng 1) than with urea and herbicide, however, that of plant parasitic nematodes exhibited an inverse trend.

Self-assembled 3D microflowery In(OH)(3) architecture and its conversion to In2O3

Using sodium dodecyl sulfate (SDS), a 3D microflowery indium hydroxide [In(OH)(3)] structure assembled from 2D nanoflakes was fabricated in a large quantity via a hydrothermal approach at relative low temperature. The obtained In(OH)(3) flowers exhibited a narrow size range between 4 and 6 mu m. The properties of these composites were characterized by XRD, EDX, FE-SEM, TEM, SAED, and TGA. In this work, both the use of urea and SDS and the amounts of these components played important roles in the formation of In(OH)3 with different nanostructures.

Indium sulfide microflowers: Fabrication and optical properties

With the assistance of urea, uniform 2D nanoflakes assembled 3D In2S3 microflowers were synthesized via a facile hydrothermal method at relative low temperature. The properties of the as-obtained In2S3 flowers were characterized by various techniques. In this work, the utilization of urea and L-cysteine, as well as the amount of them played important roles in the formation of In2S3 with different nanostructures. Inferred from their morphology evolution, a urea induced precursor-decomposition associated with the Ostwald-ripening mechanism was proposed to interpret these hierarchical structure formation.

One-step synthesis of graphene/SnO2 nanocomposites and its application in electrochemical supercapacitors

A one-step method was developed to fabricate conductive graphene/SnO2 (GS) nanocomposites in acidic solution. Graphite oxides were reduced by SnCl2 to graphene sheets in the presence of HCl and urea. The reducing process was accompanied by generation of SnO2 nanoparticles. The structure and composition of GS nanocomposites were confirmed by means of transmission electron microscopy, x-ray photoelectron and Raman spectroscopy. Moreover, the ultracapacitor characteristics of GS nanocomposites were studied by cyclic voltammograms (CVs) and electrical impedance spectroscopy (EIS). The CVs of GS nanocomposites are nearly rectangular in shape and the specific capacitance degrades slightly as the voltage scan rate is increased. The EIS of GS nanocomposites presents a phase angle close to p/2 at low frequency, indicating a good capacitive behavior.

Tunable Luminescence in Monodisperse Zirconia Spheres

In this article, monodisperse spherical zirconia (ZrO2) particles with a narrow size distribution were prepared by the controlled hydrolysis of zirconium butoxide in ethanol, followed by heat treatment in air at low temperature from 300 to 500 degrees C. X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric and differential thermal analysis (TG/DTA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL) spectra, kinetic decay, and electron paramagnetic resonance were used to characterize the samples. The experimental results indicate that the annealed ZrO2 samples exhibit broad, intense visible photoluminescence. The annealing temperature is indispensable for the luminescence of the obtained ZrO2 particles. The emission colors of the ZrO2 samples can be tuned from blue to nearly white to dark orange by varying the annealing temperature.

General and Facile Method To Prepare Uniform Y2O3:Eu Hollow Microspheres

Well-shaped Y2O3:Eu hollow microspheres have been successfully prepared on a large scale via a urea-based homogeneous precipitation technique in the presence of colloidal carbon spheres as hard templates followed by a subsequent heat treatment process. XRD results demonstrate that all the diffraction peaks of the samples can be well indexed to the pure cubic phase Of Y2O3. TEM and SEM images indicate that the shell of the uniform hollow spheres, whose diameters are about 250 nm, is composed of many uniform nanoparticles with diameters of about 20 nm, basically consistent with the estimation of XRD results. Furthermore, the main process in this method was carried out in aqueous condition, without the use of organic solvents or etching agents. The as-prepared hollow Y2O3:Eu microspheres show a strong red emission corresponding to the D-5(0)-F-7(2) transition of the Eu3+ ions under ultraviolet or low voltage excitation, which might find potential applications in fields such as light phosphor powders, advanced flat panel displays, field emission display devices, and biological labeling.

Synthesis and luminescence properties of nanocrystalline Gd2O3 : Eu3+ by combustion process

The nanocrystalline Gd2O3:Eu3+ powders with cubic phase were prepared by a combustion method in the presence of urea and glycol. The effects of the annealing temperature on the crystallization and luminescence properties were studied. The results of XRD show pure phase can be obtained, the average crystallite size could be calculated as 7, 8, 45, and 23 run for the precursor and samples annealed at 600, 700 and 800 degrees C, respectively, which coincided with the results from TEM images. The emission intensity, host absorption and charge transfer band intensity increased with increasing the temperature. The slightly broad emission peak at 610 nm for smaller particles can be observed. The ratio of host absorption to O-2-Eu3+ charge transfer band of smaller nanoparticles is much stronger compared with that for larger nanoparticles, furthermore, the luminescence lifetimes of nanoparticles increased with increasing particles size. The effects of doping concentration of Eu3+ on luminescence lifetimes and intensities were also discussed. The samples exhibited a higher quenching concentration of Eu3+, and luminescence lifetimes of nanoparticles are related to annealing temperature of samples and the doping concentration of Eu3+ ions.

Single-wall carbon nanotube-based voltammetric sensor and biosensor

The pH-sensitive property of the single-wall carbon nanotube modified electrode based oil the electroactive group on the single-wall carbon nanotube was explored by differential pulse voltammetry technique. In pH range 1-13 investigated in Britton-Robinson (B-R) buffer, the anodic peak shifted negatively along with the increase of pH exhibiting a reversible Nernstian response. Experiments were carried out to investigate the response of the single-wall carbon nanotube (SWNT) modified electrode to analytes associated with pH change. The response behavior of the modified electrode to ammonia was studied as an example. The potential response could reach equilibrium within 5 min. The modified electrode had good operational stability. Voltammetric urease and acetylcholinesterase biosensors were constructed by immobilizing the enzymes with sol-get hybrid material. The maximum potential shift could reach 0.130 and 0.220V for urea and acetylthiocholine, respectively. The methods for preparing sensor and biosensor were simple and reproducible and the range of analytes could be extended to substrates of other hydrolyases and esterases.

Synthesis and luminescence properties of Gd2O3 : Eu3+ phosphors

Gd2O3: EU3+ phosphors were prepared by urea homogeneous precipitation with different surfactant and sol-gel method. XRD patterns show that all the obtained samples are in cubic Gd2O3, and the results of FTIR and fluorescent spectra conformed that OP is a good surfactant for preparing the Gd2O3: Eu3+ phosphors. The SEM photographs show that the particles prepared by urea homogeneous precipitation method are all spherical and well-dispersed, and grain morphology can be controlled by different surfactant. XRD and SEM indicate that the particle sizes prepared by sol-gel method are in the range of 5 similar to 30 nm, and the grain sizes increase with increasing of heated temperatures. Luminescence spectra indication that the main emission peaks of all samples are at 610 nm, the intensities are different from samples prepared with different surfactant and the luminescence intensities increase with increasing of annealed temperatures.