微生物环氧化合物水解酶在有机合成中的应用

环氧化合物水解酶是一种在自然界广泛存在的水解酶 ,它能高对映体选择性、高区域选择性地将环氧化合物水解为相应的邻位二醇。近年来 ,国际上利用微生物环氧化合物水解酶催化的不对称水解反应获得了高光学纯度环氧化合物和邻二醇 ,可用于多种精细化学品和生物活性物质的合成 ,为该酶在合成工业上的应用开辟了一条新途径。这里综述了该酶的来源、催化机理。

水稻水溶性环氧化合物水解酶的生物信息学分析

水溶性环氧化合物水解酶(Soluble Epoxide Hydrolase,SEH)是一组催化环氧化合物水解为相应邻位二醇的酶类,在哺乳动物、植物、昆虫和微生物体内广泛存在。通过BLAST对水稻基因组的蛋白质数据库进行搜索,获得10个水溶性环氧化物水解酶(Soluble Epoxide Hydrolase SEH)sEH蛋白的同源序列。经分析发现这些基因在水稻不同胁迫处理下各个部位都有所表达,而且不同成员之间的表达模式存在较大的差异。水稻sEH蛋白主要参与角质层形成,应激反应,以及病原防御等生理过程,特别在脱毒过程中扮演着重要的角色。对蛋白质多序列联配和三级结构预测结果表明:水溶性环氧化合物水解酶的核心结构域由3个催化残基Asp、His和Asp形成三位一体的催化活性构象。这类基因的表达受抗逆环境诱导,其功能与抗逆性有关,为基因工程抗逆育种提供了参考。

纳米级高活性聚酯催化剂合成及应用技术研究

在反应器中加入易水解钛化合物、二元醇及缓释剂,搅拌使之反应形成凝胶,再加入氧化剂。其中易水解钛化合物与二元醇的摩尔比为0.0009-0.3:1.0;缓释剂为钛酸酯用量的5-10%;氧化剂与钛酸酯的摩尔比为1.2-1.5:1.0。加热升温,通入惰性气体或抽真空逐步排出反应系统中生成的低分子化合物,使凝胶转化为固体物,将此固体物进行离心分离或真空抽滤,滤液回收循环利用,固体物经工业乙醇或丙酮等低沸点溶剂洗涤脱色、干燥,即得到化学式为C_nH_(2n)+1O_5Ti的抗水解高活性钛系聚酯催化剂,其在二元醇中经常规搅拌或超声波分散后,在催化聚酯缩聚反应中催化剂活性超过锑系催化剂。

姬松茸固态发酵对小麦多酚的影响

为研究姬松茸固态发酵对小麦多酚的影响并初步探索其代谢机理,对姬松茸固态发酵后小麦的多酚物质(游离态多酚、结合态多酚和总酚)含量和3种碳水化合物水解酶(纤维素酶、α-淀粉酶和β-葡萄糖苷酶)酶活性进行了测定,并对它们之间的关系进行了研究。结果表明,游离态多酚和总酚含量随发酵时间的延长而增加,均在发酵30 d时达到最大,分别为3.121 mg/g和3.207 mg/g。结合态多酚含量随发酵时间的延长而降低。纤维素酶和α--淀粉酶的酶活性随发酵时间的延长而增加,在发酵第20 d达到最大,之后逐渐降低。β--葡萄糖苷酶的酶活在5~30 d的发酵时间内一直随发酵时间延长而增加。3种酶对结合态多酚从细胞壁释放出来起重要作用。

Chemical characterization and composition of dissolved organic matter in Jiaozhou Bay

Biologically utilizable dissolved organic compounds,including dissolved organic carbon (DOC),dissolved carbohydrates (DCHO) and dissolved free amino acids (DFAA) were analyzed in filtered surface seawater samples collected at 19 stations in Jiaozhou Bay,China,on June 3,2007.In these samples,concentrations of DOC,dissolved free carbohydrates (DFCHO),dissolved combined carbohydrates (DCCHO),total dissolved carbohydrates (TDCHO) and total dissolved free amino acids (TDFAA) ranged from 141.7 to 191.1 μmol C/L,1.98 to 18.18 μmol C/L,5.04 to 24.90 μmol C/L,14.52 to 30.36 μmol C/L,and 1.83 to 11.89 μmol C/L,respectively.As a major component of the dissolved carbohydrates,the concentrations of DCCHO were about three times higher than those of DFCHO.Three major constituents of the DFAA were threonine (23.0±5.7 mol%),glutamic acid (16.6±3.2 mol%) and arginine (9.1±3.3 mol%).Based on the composition of DFAA,a molar C:N ratio of 3.60±0.75 in DFAA was derived,indicating longer carbon chains in the amino acids.DCCHO (8.1%) was the most abundant fraction of DOM in most samples,followed by DFCHO (4.8%) and TDFAA (2.7%).These DOM concentrations displayed a decreasing trend from the coast to the central region.Significant correlations were found between the DCCHO and DFCHO concentrations (r=-0.724,n=19,P<0.001) and the DCCHO and TDCHO concentrations (r=0.506,n=19,P=0.027).

Degradation of Wastewater Containing Nitrobenzene by High Gravity-Ultrasonic/Ozonation/Electrolysis Technology

The integrated high gravity-ultrasonic/ozonation/electrolysis technology was applied in the pretreatment of wastewater containing nitrobenzene. The effect ofpH value, high gravity factor, liquid flow-rate and electric current density on removal of COD and nitrobenzene compounds was investigated. Experimental results have determined the optimal pro- cess regime involving a high gravity factor of 100, an electric current density of 20 mA/cm2, a liquid flow-rate of 100 L/h, and an initial liquid pH value of 11. After the wastewater had been treated for 180 rain, the degradation of nitrobenzene and COD reached 99% and 80%, respectively, with the biochemical coefficient （BOD/COD） equating to 0.64, and the subse- quent treatment of wastewater could be carried out by conventional biochemical means. Compared with traditional aeration- ozone contactors, a rotating packed bed with high mass transfer characteristics could be used to increase the ozonation treat- ment efficiency.

High efficiency production of ginsenoside compound K by catalyzing ginsenoside Rb1 using snailase

The rare ginsenoside Compound K （C-K） is attracting more attention because of its good physiological activity and urgent need. There are many pathways to obtain ginsenoside C-K, including chemical and biological methods. Among these, the conversion of PPD-type ginsenosides by enzymatic hydrolysis is a trend due to its high efficiency and mild conditions. For effectively extracting from the other panaxadiol saponins, the conversion process for ginsenoside C-K was investigated using snailases in this study. The univariate experimental design and response surface methodology were used to determine the optimal hydrolysis conditions for the conversion of ginsenoside Rbl into ginsenoside C-K by snailases. The optimum conditions were as follows： pH 5,12, temperature 51 ℃, ratio of snailase/substrate 0.21, and reaction time 48 h. On the basis of these parameters, the addition of 1.0 mmol· L- 1 ferric ion was found to significantly improve the enzymolysis ofsnailases for the first time. With the above conditions, the maximum conversion rate reached 89.7%, suggesting that the process can obviously increase the yield of ginsenoside C-K. The bioassay tests indicated that the ginsenoside C-K showed anti-tumor activity in a series of tumor cell lines. Based on these results, we can conclude that the process of rare ginsenoside C- K production by enzymolysis with snailase is feasible, efficient, and suitable for the industrial production and application.

Biochar-based Solid Acids as Catalysts for Carbohydrate Hydrolysis: A Critical Review

Recently, increasing interest has been focused on the hydrolysis of carbohydrates to monosaccharides, among which, glucose and xylose as typical platform sugars can be used to produce chemicals and biofuels. As heterogeneous catalysts, solid acids have gained extensive attention for biomass biorefinery and could replace the conventional process owing to their excellent properties, including acceptable acidity and easy separation. In particular, biochar-based solid acids derived from biomass are promising for biomass conversion owing to the low-cost of feedstocks and the simple preparation procedure. Herein, we attempt to provide a critical overview of biochar-based solid acids for hydrolysis of carbohydrates into glucose and xylose. The preparation methods and properties of biochar-based catalysts as well as the influence of their properties on catalytic performance were discussed in detail. We also highlight the major challenges facing the use of biochar-based solid acids for carbohydrate hydrolysis.

Hydrolysis of Carbonyl Sulfide in Binary Mixture of Diethylene Glycol Diethyl Ether and Water

The solubility and hydrolysis of carbonyl sulfide in binary mixture of diethylene glycol diethyl ether and water are studied as a function of composition. The use of an aqueous solution of diethylene glycol diethyl ether enhances the solubility and hydrolysis rate of carbonyl sulfide compared with that in pure water. The composition of the mixture with maximum hydrolysis rate varies with temperature. The thermophysical properties including density, viscosity, and surface tension as a function of composition at 20℃ under atmospheric pressure as well as liquid-liquid equilibrium (LLE) data over the temperature range from 28℃ to 90℃ are also measured for the binary mixture.

Spatiotemporal variation of dissolved carbohydrates and amino acids in Jiaozhou Bay,China

Surface seawater samples were collected from Jiaozhou Bay,China,during six cruises(MarchMay 2010,September-November 2010) to study the distribution of dissolved organic matter including dissolved organic carbon(DOC),total dissolved carbohydrates,namely monosaccharides(MCHO) and polysaccharides(PCHO) and total hydrolysable amino acids.These included dissolved free amino acids(DFAA) and combined amino acids(DCAA).The goal was to investigate possible relationships between these dissolved organic compounds and environmental parameters.During spring,the concentrations of MCHO and PCHO were 9.6(2.8-22.6) and 11.0(2.9-42.5) μmol C/L,respectively.In autumn,MCHO and PCHO were 9.1(2.6-27.0) and 10.8(2.4-25.6) μmol C/L,respectively.The spring concentrations of DFAA and DCAA were 1.7(1.1-4.1) and 7.6(1.1-31.0) μmol C/L,respectively,while in autumn,DFAA and DCAA were 2.3(1.1-8.0) and 3.3(0.6-7.2) μmol C/L,respectively.Among these compounds,the concentrations of PCHO were the highest,accounting for nearly a quarter of the DOC,followed by MCHO,DCAA and DFAA.The concentrations of the organic compounds exhibited a decreasing trend from the coastal to the central regions of the bay.A negative correlation between concentrations of DOC and salinity in each cruise suggested that riverine inputs around the bay have an important impact on the distribution of DOC in the surface water.A significant positive correlation was found between DOC and total bacteria count in spring and autumn,suggesting bacteria play an important role in the marine carbon cycle.

Physical Simulation of Water Dissolved Gas (WDG)During Migration

By using the equipment designed and developed by ourselves, experiment of investigating the influence of dissolution on some geo-chemical parameters (such as δ13C,δD,and iC4/nC4 in water-dissolved gas (WDG) during migration) was performed. The result shows that, with the increase of distance, 1) the relative abundance of non-hydrocarbon (CO2) and hydrocarbon (CH4) increase while the relative abundance of hydrocarbon (C2+) decreases (the relative abundance of hydrocarbon (C5+) can be basically negligible); 2) the relative abundance of benzene and methylbenzene increase in the initial time and then decrease. The carbon and hydrogen isotopes of methane vary slightly, which can be regarded as indicators of gas dissolved in water formation.

COD Removal Efficiencies of Some Aromatic Compounds in Supercritical Water Oxidation

Some aromatic compounds, phenol, aniline and nitrobenzene, were oxidized in supercritical water. It was experimentally found that the chemical oxygen demand (COD) removal efficiency of these organic compounds can achieve a high level more than 90% in a short residence time at temperatures high enough. As temperature, pressure and residence time increase, the COD removal efficiencies of the organic compounds would all increase. It is also found that temperature and residence time offer greater influences on the oxidation process than pressure. The difficulty in oxidizing these three compounds is in the order of nitrobenzene ＞ aniline ＞ Phenol. In addition, it is extremely difficult to oxidize aniline and nitrobenzene to CO2 and H2O at the temperature lower than 873.15 K and 923.15 K, respectively. Only at the temperature higher than 873.15 K and 923.15 K, respectively, the COD removal efficiencies of 90% of aniline and nitrobenzene can be achieved.

Preparation of Photocatalytic TiO_2 and TiO_2-SiO_2 Particles and Application to Degradation of Trace Organics in Aqueous Solution

TiO2 and TiO2-SiO2 photocatalysts were prepared by sol-gel and supercritical CO2 fluid drying method and characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), etc. Their catalytic properties were tested through the photocatalytic degradation of phenol and aniline in wastewater. The results show that the developed fluidized photocatalytic reactor (FPR) and TiO2 catalyst had better performance in degrading pollutants as compared with slurry photocatalytic reactor (SPR) and commercial TiO2 catalyst. The composition and crystal form of TiO2-SiO2 composite oxide had obvious influence on catalytic effect and TiO2-SiO2 photocatalysts showed better catalytic activity and stability.

Pyrolysis of Banana and Coffee Residues after Acid Hydrolysis

The use of the residues from renewable feedstock, besides the production of fuels, but also for the generation of other chemicals products, has become a priority. Superior plants have considerable potential as carbohydrate, aryl and fatty acids sources. However, the separation of the main constituents of the samples is necessary for several purposes in the biorefinery concept. The acid hydrolysis and pyrolysis processes are very promising technology, however, some adjustments in the conditions of pyrolysis are needed for different biomasses since carbohydrates were detected （14%-17%） in the residues after the conventional acid hydrolysis of these uncommon biomasses （coffee husk and banana stem and stalk）. On the other hand, it was showed that, by pyrolysis, it is possible to obtain from the solid residue after acid hydrolysis： pyrogenic carbon （charcoal with a yield of 48.5%-52.7%） for agriculture use （biochar） and valuable chemicals in the pyrolysis oil biooil fraction （that accounted by 26.4%-29.0%, free of water）, such as lignin monomers （32.6%-56.4% of the bio-oil） and fatty acids （30%-52.5%）.

Theoretical On-Board Hydrogen Redox Electric Power Generator for Infinite Cruising Range Fuel Cell Vehicles

The development of hydrogen redox electric power generators for infinite cruising range electric vehicles represents a true technological breakthrough. Such systems consist of a polymer electrolyte membrane hydrogen electrolytic cell equipped with an electrostatic-induction potential-superposed water electrolytic cell that provides a stoichiometric H2-O2 fuel mixture during operation of the vehicle. This generator functions with zero power input, zero matter input and zero emission due to the so-called ＂zero power input＂ electrostatic-to-chemical energy conversion occurring in the electrolytic cell. Here, theoretical simulations were performed to verify the target performance of such generators, assuming a pair of FC （fuel cell） and electrolytic cell stacks, both of which are commercially available.