阴离子交换树脂固定化果胶酶及其酶学性质的研究

以阴离子交换树脂为载体,戊二醛为交联剂,对果胶酶进行先吸附后交联的固定化,研究吸附温度、吸附pH值、吸附时间、加酶量、戊二醛浓度、交联温度、交联时间对果胶酶固定化效果的影响,同时对固定化果胶酶的特性进行了研究。研究表明,最佳固定化条件为:温度40°C,pH 5.5,固定化6 h,加酶量0.75 mL/g树脂(浓度为1%酶液),戊二醛交联浓度0.1%,交联温度4°C,交联时间4 h。酶学特性研究表明,固定化果胶酶在最适温度60°C,最适pH 4.0下具有较好的操作稳定性。     

吸附树脂吸附蜂蜜中羟甲基糠醛的热力学研究

为考察大孔吸附树脂对蜂蜜中羟甲基糠醛(HMF)的吸附可行性，该文采用静态吸附法研究了LSA-800B型大孔树脂对HMF吸附过程的热力学性质。结果表明，在298，308，318 K和研究的浓度范围内，蜂蜜中的HMF在LSA-800B型树脂上的吸附等温线均符合Freundlich等温吸附方程，Freundlich吸附等温线和等量吸附焓表明LSA-800B型树脂对蜂蜜中HMF吸附是放热过程。吸附自由能ΔG＜0表明吸附的自发性，吸附熵变ΔS＜0说明吸附质分子在吸附树脂表面上的运动比在溶液中受到更大的限制。     

几种吸附剂对阿特拉津的吸附及其 Zeta 电位特性研究

通过振荡吸附平衡试验,研究了蒙脱石、凹凸棒石、竹炭、木炭对阿特拉津的吸附行为,讨论了pH值、离子强度对吸附的影响,并考察了吸附剂表面的Zeta电位变化。结果表明,几种吸附剂对阿特拉津的吸附均符合Freundlich方程;竹炭、木炭的吸附能力明显高于蒙脱石和凹凸棒石。吸附剂对阿特拉津的吸附量随着悬液离子强度的增加而增加,在悬液pH一定(pH=6),离子强度为10-3mol/L NaNO3时,蒙脱石、凹凸棒石对阿特拉津的吸附量分别为538.30、609.68 mg/kg,当离子强度增加为10-2mol/L时,吸附量分别增至611.26、731.63 mg/kg;当离子强度由10-3增至10-1mol/L NaNO3时,竹炭、木炭对阿特拉津的吸附量有较多增加。当悬液pH在3~8范围时,几种吸附剂表面均带负电荷,其Zeta电位值随着pH的增加而增加,随离子强度的增加而减小。悬液离子强度一定时,随着pH的增加,吸附阿特拉津后吸附剂表面Zeta电位变化不显著。研究结果有助于从机理上解析吸附剂对有机污染物的吸附行为。     

Kinetic properties and stability of potato acid phosphatase immobilized on Ca-polygalacturonate

 Acid phosphatase from potato was adsorbed and immobilized on a pre-formed network of Ca-polygalacturonate, a substrate which has a composition and morphology similar to the mucigel present at the root-soil interface. The influence of different types of organic buffers on enzyme adsorption and activity was investigated. The highest enzyme activity, for free and adsorbed enzyme, was obtained with Na-maleate buffer at pH 6.0, which was used for all subsequent experiments. The Michaelis-Menten kinetic parameters, V_max and K_m, were determined for free and adsorbed phosphatase. V_max showed a 60% decrease upon adsorption (2.09±0.30 U/mg, for the soluble form and 0.84±0.15 U/mg, for the adsorbed enzyme), whereas K_m increased from 0.49±0.15 mM for the free enzyme to 0.99±0.20 mM for adsorbed phosphatase. Phosphatase adsorption decreased as the concentration of NaCl increased, indicating that the enzyme is bound to the carrier gel through coulombic interactions. Adsorption increased stability of the enzyme as compared with the free enzyme (t _1/2 of the activity was 9.4 days and 5.8 days, respectively), but increased thermal and proteolytic inactivation. The pH/activity profile revealed no change in terms of shape or optimum pH (4.5) upon adsorption of the enzyme. These results indicate that adsorption of acid phosphatase on Ca-polygalacturonate induces changes in the kinetic properties and stability of the enzyme, and the same type of response can be extrapolated from these results for acid phosphatases of the rhizosphere. Received: 1 July 1997     

Synthesis and sensorial properties of mercaptoaldehydes

Mercaptoalcohols and mercaptoketones have been described in the past decade as relevant character-impact compounds in various food products. On the other hand, very little is known of mercaptoaldehydes. Only 3-mercapto-2-methylpentanal and 3-mercaptohexanal have been found in onions and beef liver, respectively. The aim of this work was to synthesize 13 mercaptoaldehydes not commercially available by combinatorial chemistry. Chromatographic analyses of the mixture allowed the determination of their retention indices and mass spectroscopy fragments for further identification in foods. Gas chromatography-olfactometry demonstrated how some of them are characterized by unusual odor and very low perception threshold.     

Adsorption and desorption properties of macroporous resins for anthocyanins from the calyx extract of roselle (Hibiscus sabdariffa L.)

Adsorption of roselle anthocynins, a natural pigment, onto various macroporous resins was optimized to develop a simple and efficient process for industrial separation and purification of roselle anthocyanins. Nine different macroporous resins (AB-8, X-5, HPD-100, SP-207, XAD-4, LS-305A, DM-21, LS-610B, and LS-305) were evaluated for the adsorption properties of the anthocyanins extracted from the calyx extract of Hibiscus sabdariffa L. The influences of phase contact time, solution pH, initial anthocyanin concentration, and ethanol concentration with different citric acid amounts were studied by the static adsorption/desorption method. The adsorption isotherm data were fitted well to the Langmuir isotherm, and according to this model, LS-610B and LS-305 exhibited the highest monolayer sorption capacities of 31.95 and 38.16 mg/g, respectively. The kinetic data were modeled using pseudo-first-order, pseudo-second-order, and intraparticle diffusion equations. The experimental data were well described by the pseudo-second-order kinetic model. Continuous column adsorption-regeneration cycles indicated negligible capacity loss of LS-305 during operation. The overall yield of pigment product was 49.6 mg/g dried calyces. The content of roselle anthocynins in the pigment product was 4.85%.     

Modification of the rheological properties of whey protein isolate through the use of an immobilized microbial transglutaminase

A process was developed in which calcium-independent, microbial transglutaminase (mTgase) was immobilized to controlled-pore glass. Avidin was adsorbed to glass beads that had been derivatized and biotinylated. The enzyme was biotinylated and adsorbed to the avidin affinity matrix. Solutions of 8% whey protein isolate (WPI) were then incubated with the mTgase beads, resulting in limited cross-linking of whey proteins. As incubation time increased, intrinsic viscosity increased, gelation temperature decreased, and stronger, more brittle gels were formed upon heating. This process allowed for recycling of the enzyme, eliminated the requirement for a downstream inactivation step, and permitted control over the extent of cross-linking. The functional properties of several batches of WPI were modified using <10 mg of the same enzyme, illustrating the capacity of immobilized enzymes to be used more frequently in applications of this nature.     

Quantitative relationship between soil properties and adsorption of dissolved organic matter onto volcanic ash and non-volcanic ash soils

The formation of soil organo-mineral complexes is a key reaction in the carbon cycle in soil, since organic materials acquire a resistance to decomposition due to the formation of the complexes. Adsorption of dissolved organic matter (DOM) onto soil minerals provides a model of this important process. Adsorption of DOM onto samples from Andisols, Inceptisols, and Entisols in batch experiments was compared in terms of the quantitative relationship between the soil properties and the adsorption behavior of DOM. Adsorption behavior was effectively described by a linear initial mass (IM) isotherm, indicating that the adsorption efficiency did not appreciably decline in the range studied even though a large amount of DOM was applied to the soil samples. Samples from Andisols showed a particularly high efficiency of adsorption compared with those from other soils which contained a comparable amount of organic carbon. Explanatory variables useful to predict the efficiency parameter were investigated in 2 steps: firstly the degree of carbon accumulation in the soil samples was examined, and next an index for the amount of ligand exchange sites was examined in combination with the former indices. As a result, an index comprising the total carbon/clay (or total carbon/specific surface area) ratio and the amount of hydroxy ions in the soil extracts with NaF solution was eventually detected. The former represents the degree of carbon occupation on the soil surface, and the latter the amount of ligand exchange sites on labile aluminum. Although the mechanisms involved in the adsorption varied among soils, the selected index was significantly correlated with the adsorption efficiency.     

基于纤维素酶和果胶酶活力的康氏木霉固体发酵培养基配方研究

为找到廉价的优化培养基配方生产高活力的复合纤维素酶,该实验采用配方试验和双温度培养法对康氏木霉F244菌株进行固体发酵,测定滤纸酶、棉花酶、羧甲基纤维素酶、β-葡萄糖苷酶、果胶酶活力并通过SPSS软件建立回归方程,其全相关系数分别达到0.852,0.941,0.964,0.703,0.899,而后利用无约束规划求解找到复合酶生产配方.结果表明在固体培养基中Tween80对纤维素酶和果胶酶的生产均存在抑制作用,理想固体产酶培养基是稻草粉、麸皮、(NH4)2SO4及水分的混合物;复合纤维素酶生产的适宜配方为稻草粉16%,麸皮24%、(NH4)2SO4 3%、含水率57%,该配方对应的滤纸酶、棉花酶、羧甲基纤维素酶、β-葡萄糖苷酶及果胶酶的期望酶活分别达到72,129,342,112和108g.     

Adsorption behavior of the catechins and caffeine onto polyvinylpolypyrrolidone

Adsorbent is one of the most important factors for separation efficiency in fixed-bed purification techniques. The adsorption behavior of catechins and caffeine onto polyvinylpolypyrrolidone (PVPP) was investigated by static adsorption tests. The results showed that catechins rather than caffeine were preferred to adsorb onto PVPP since the adsorption selectivity coefficient of total catechins vs caffeine was around 22.5, and that adsorption of catechins could be described by the pseudo-second-order model. Adsorption amount of caffeine onto PVPP in green tea extracts solution was much higher than that in purified caffeine solution although the initial concentration of caffeine was similar in the two solutions, indicating the caffeine might be attached with catechins which were adsorbed by PVPP instead of being adsorbed by PVPP directly. The results also showed that the adsorption capacity of catechins and caffeine decreased with an increase in temperature, and that Freundlich and Langmuir models were both suitable for describing the isothermal adsorption of catechins, but not suitable for caffeine. The predicted maximum monolayer adsorption capacity of total catechins by PVPP was 671.77 mg g(-1) at 20 °C, which was significantly higher than that by other reported adsorbents. The thermodynamics analyses indicated that the adsorption of catechins onto PVPP was a spontaneous and exothermic physisorption process, revealing lower temperature was favorable for the adsorption of catechins. Elution tests showed that the desorption rates of catechins and caffeine were higher than 91% and 99% after two elution stages; in detail, almost all of the caffeine could be washed down at the water eluting stage, while catechins could be recovered at the dimethyl sulfoxide/ethanol solution eluting stage. Thus, the PVPP could be used as an excellent alternative adsorbent candidate for separating catechins from crude tea extracts, although some investigations, such as exploring the new eluants with low boiling point and high desorption efficiency, should be conducted furthermore.     

大孔树脂纯化香蕉皮缩合单宁的吸附特性分析与工艺优化

为提高香蕉皮缩合单宁提取物纯度,提升其后续研究与利用价值,该研究采用大孔树脂吸附法纯化香蕉皮缩合单宁,通过比较6种大孔树脂的吸附与解吸性能,筛选出最适宜的树脂型号,并从动力学和热力学的角度分析该树脂对香蕉皮缩合单宁的吸附特性,探究其纯化工艺条件。结果表明：HP-20型大孔树脂是纯化香蕉皮缩合单宁的适宜树脂;静态吸附-解吸动力学试验表明HP-20树脂分别在8、5 h内能够完成对香蕉皮缩合单宁的吸附、解吸过程,该吸附过程符合伪二阶动力学方程(R²=0.997 2);Freundlich热力学模型适用于解释树脂与缩合单宁间的相互作用,这是一种发生在多分子层表面的吸附,模型常数K_F与温度成正相关,表明升温利于吸附的进行;热力学参数计算结果为ΔG<0（-9.75、-9.70、-8.83 kJ/mol）,ΔH=5.13 kJ/mol,ΔS=47.28 J/mol·K,进一步证明了该过程是自发的、吸热的过程,且物理吸附占据主导作用,无序性有所增加。较佳的纯化参数是上样浓度为6 mg/mL、上样流速为1.5 mL/min、上样量为200 mL、洗脱液乙醇浓度为70%、洗脱流速为1.5 mL/min、洗脱液用量为120 mL。经该条件纯化后,香蕉皮缩合单宁纯度由5.79%提高到68.44%。说明HP-20树脂和优化参数对香蕉皮缩合单宁的纯化效果良好。     

Effect of tillage systems and polyacrylamide on soil physical properties and wheat grain yield in arid regions differing in fine soil particles

A field study was performed for two consecutive seasons to evaluate the effect of polyacrylamide (PAM), tillage systems and particle size on soil physical properties and wheat grain yield. The PAM rates were 0, 10 and 20 kg ha^?1 while the tillage treatments included no-tillage (NT), moldboard plowing (CT1), and chisel plowing (CT2). Soil fine particles size of two locations were A (25.2 silt + clay) and B (38.5 silt + clay). Location B reported higher organic matter and total porosity while lower in bulk density. The CT1 and NT treatments denoted better soil organic matter percentage. The CT1 presented maximum infiltration rate compared to other tillage systems. No tillage showed better soil water contents while the minimum was in CT1 of location A and CT2 of location B. Increasing the PAM rate increased total porosity, infiltration rate and soil water content while decreased soil bulk density. Possibly, the presence of compacted layer in location A hindered the effect of PAM. At location B, the CT2 with PAM of 20 kg ha^?1 had the highest grain yield compared to other tillage systems. The PAM is beneficial for soil and water conservation and can be used in agriculture.     

大孔吸附树脂分离纯化罗汉果皂甙的新方法

该文对大孔树脂分离纯化高含量罗汉果皂甙提取物的新方法进行了研究。结果表明：大孔树脂D101对罗汉果皂甙的分离效果较好,最佳柱分离条件为：上样液pH值9.0,在40℃下依次用pH值9.0的碱水溶液、蒸馏水、30%乙醇及60%乙醇进行洗脱,将60%乙醇洗脱液浓缩,冷冻干燥即得高含量罗汉果皂甙提取物。高效液相分析表明,罗汉果皂甙中几种主要成分的含量均高于分离前的罗汉果皂甙水提物,其中罗汉果皂甙V的含量为69.24%,提高了41.12%。     

Organic matter and polyacrylamide amendment of Norfolk loamy sand

Loamy sand soils of the southeastern USA Coastal Plains often have poor physical properties because they contain cemented subsurface hard layers that restrict root development and yield. Their physical properties can be improved by adding amendments. Polyacrylamide (PAM) amendments and/or organic matter (OM) in the form of ground wheat (Triticum aestivum L.) stubble or pecan (Carya illinoensis) branches were mixed into a blend of 90% E horizon and 10% Ap horizon (to assure microbial presence) obtained from a Norfolk soil (Acrisol or fine-loamy, siliceous, thermic Typic Kandiudult). We hypothesized that incorporation of these amendments would improve soil physical properties by reducing strength and improving aggregation. Amended treatments contained 450 g of soil, OM, and 30 or 120 mg kg⁻¹ of PAM (12 mg mol⁻¹, anionic, and 35% charge density); treatments were incubated for 96 days at 10% (w/w) water content. Twice during the incubation period, treatments were leached with 1.3 pore volumes of deionized water. After leaching and equilibrating to stable water contents, treatments were analyzed for bulk densities and probed with a 5-mm diameter flat-tipped bench-top penetrometer to measure penetration resistances. Though penetration resistances increased for the highest level of PAM amendment, they showed no significance when both PAM and OM were added to the soil. When compared to controls, treatments with PAM at 120 mg kg⁻¹ had decreased bulk densities. Treatments with both rates of PAM had decreased requirements for water needed to maintain treatments at 10% water contents. Aggregation increased with increasing amounts of PAM but showed no consistent trend when both PAM and OM were added to the soil. Because PAM increased aggregation and water holding capacities in these coastal soils, it could reduce the need for deep tillage. However, more work needs to be done to determine an effective mix of PAM and OM.     

Lactones. 21. Synthesis and odoriferous properties of lactones with the p-menthane system

Starting from (R)-(+)- and (S)-(-)-pulegone, enantiomeric pairs of esters and lactones with the p-menthane system were obtained. The Claisen rearrangement of allylic alcohols and iodolactonization of gamma,delta-unsaturated acids were the key steps of syntheses presented. The structures of compounds were determined by both spectroscopic and crystallographic methods. Some of the synthesized compounds are characterized by interesting odoriferous properties.     

稀土农膜转光材料合成与性质研究

采用乙醇 水溶液析出法合成了 1 1种以稀土三价铕离子为中心离子 ,以 β二酮 (α 噻吩甲酰三氟丙酮、二苯甲酰甲烷、苯甲酰丙酮 )和芳香羧酸 (肉桂酸、烟酸 )为主配体 ,有机胺类 (邻菲咯啉、三辛胺、三乙胺 )为协同配体的二元及三元配合物 ,通过荧光光谱和TG DTA谱线分析配合物荧光性能及热力学稳定性结果表明 ,所合成的配合物中仅三 (α 噻吩甲酰三氟丙酮根 ) (邻菲咯啉 )·合铕 (Ⅲ )和三 (二苯甲酰甲烷根 ) (邻菲咯啉 )·合铕 (Ⅲ )荧光强度高于对照 ,且依次为三 (α 噻吩甲酰三氟丙酮根 ) (邻菲咯啉 )·合铕 (Ⅲ ) >三 (二苯甲酰甲烷根 ) (邻菲咯啉 )·合铕 (Ⅲ ) >对照。三 (α 噻吩甲酰三氟丙酮根 ) (邻菲咯啉 )·合铕 (Ⅲ )和三 (二苯甲酰甲烷根 ) (邻菲咯啉 )·合铕 (Ⅲ )起始分解温度分别为 2 2 0℃和 2 5 0℃ ,高于膜的加工温度 ,可满足生产需要。而三 (二苯甲酰甲烷根 ) (邻菲咯啉 )·合铕 (Ⅲ )生产成本低于对照和三 (α 噻吩甲酰三氟丙酮根 ) (邻菲咯啉 )·合铕 (Ⅲ ) ,因而更具竞争优势     

大孔树脂分离纯化柚皮黄酮的研究

该文以总黄酮含量和总黄酮回收率为考察指标，研究了大孔树脂分离纯化柚皮黄酮的工艺。结果表明：AB-8型树脂对柚皮总黄酮有较好的吸附分离性能，是分离纯化柚皮黄酮的适宜大孔树脂；AB-8型大孔树脂分离纯化柚皮黄酮的最佳工艺条件为：柱体积为160 mL，柚皮提取物上样量为62.5 mg/mL(以湿树脂体积计)，先用pH 4的水淋洗，再用30%的乙醇洗脱，洗脱剂用量为2.5～3倍湿树脂体积。AB-8大孔树脂按上述确定的吸附洗脱条件可重复使用3次。柚皮黄酮经上述工艺纯化后总黄酮含量达到39.67%，总黄酮回收率为62.48%。对经AB-8大孔树脂纯化后的柚皮黄酮进行高效液相色谱(HPLC)分析发现，柚皮黄酮主要为黄酮甙类。     

油梨皮黄酮提取及大孔树脂纯化

该文研究了油梨皮黄酮的提取及大孔树脂纯化条件.结果表明:油梨皮黄酮的最佳提取条件为乙醇浓度70%、提取温度70℃、提取时间1.5 h、料液比(m/V)1:20.乙醇浓度和提取温度对提取得率有显著性(P<0.05)影响.在此条件下,黄酮的提取得率为1.12%;AB-8型树脂对油梨皮黄酮有较好的吸附和洗脱效果,其纯化油梨皮黄酮的条件为柱体积250 mL,上样量2.03 g,水洗,接着用75%的乙醇洗脱(约500 mL),在此条件下AB-8型树脂可重复使用6次.经纯化后油梨皮黄酮相对纯度为82.37%,纯化后总黄酮回收率为71.65%.     

聚丙烯酰胺对几种植物种子萌发及生长的影响

用不同浓度聚丙烯酰胺溶液处理苜蓿、狗尾草、沙棘等8种草本、灌木植物发芽试验结果表明,聚丙烯酰胺溶液浓度为0.1-1.0g/kg时,对鸡眼草、沙棘、苜蓿、草木樨种子萌发有促进作用,对其幼苗苗高、根长的影响除个别有较小抑制作用外,均表现促进作用。当溶液浓度为0.5g/kg时,对兴安胡枝子种子幼苗的根系生长则表现出显著抑制作用,而对荆条种子萌发表现出极显著抑制作用。聚丙烯酰胺各处理浓度均对黄白草、狗尾草萌发表现出极显著或显著抑制作用,而对其幼苗苗高、根长表现出显著促进或较小的抑制作用。