Cholesterol‐lowering effect of plant sterols

Intake of plant sterols (4‐desmethyl sterols, phytosterols) reduces cholesterol absorption and lowers serum total and LDL cholesterol levels in humans. The use of dietary plant sterol regimens for lowering elevated serum cholesterol values has recently gained much interest, especially after the commercial introduction of margarines containing plant stanols esterified with fatty acids. The solubility of free, crystalline plant sterols and stanols in edible oils and fats is low, limiting their use especially in fat‐containing food. By esterifying of, e.g., plant stanols with fatty acids derived from a vegetable oil fatty acid ester of plant stanols with fat‐like properties are obtained. These fat‐soluble forms of plant stanols provide a technically feasible way of introducing the adequate daily amount of plant sterol into foods for optimal reduction of the cholesterol absorption, without changing the taste of the finished product. The cholesterol‐lowering effect of plant stanol esters has been extensively studied. Plant stanol esters effectively restrict the absorption of both dietary and biliary cholesterol causing plant stanol specific reductions in serum total and LDL cholesterol levels of up to 10% and 14%, respectively. Serum HDL cholesterol and triglyceride levels are not affected. The cholesterol‐lowering effect of plant stanol esters complements the beneficial effects of a healthy diet and cholesterol medication.     

Comparative health effects of margarines fortified with plant sterols and stanols on a rat model for hemorrhagic stroke

There is increased acceptance of fortifying habitual foods with plant sterols and their saturated derivatives, stanols, at levels that are considered safe. These sterols and stanols are recognized as potentially effective dietary components for lowering plasma total and LDL cholesterol. Our previous studies have shown that daily consumption of plant sterols promotes strokes and shortens the life span of stroke-prone spontaneously hypertensive (SHRSP) rats. These studies question the safety of plant sterol additives. The present study was performed to determine whether a large intake of plant stanols would cause nutritional effects similar to those seen with plant sterols in SHRSP rats. Young SHRSP rats (aged 26–29 d) were fed semipurified diets containing commercial margarines fortified with either plant stanols (1.1 g/100 g diet) or plant sterols (1.4 g/100 g diet). A reference group of SHRSP rats was fed a soybean oil diet (0.02 g plant sterols/100 g diet and no plant stanols). Compared to soybean oil, both plant stanol and plant sterol margarines significantly (P<0.05) reduced the life span of SHRSP rats. At the initial stages of feeding, there was no difference in the survival rates between the two margarine groups, but after approximately 50 d of feeding, the plant stanol group had a slightly, but significantly (P<0.05), lower survival rate. Blood and tissue (plasma, red blood cells, liver, and kidney) concentrations of plant sterols in the plant sterol margarine group were three to four times higher than the corresponding tissue concentrations of plant stanols in the plant stanol group. The deformability of red blood cells and the platelet count of SHRSP rats fed, the plant sterol margarine were significantly (P<0.05) lower than those of the plant stanol margarine and soybean oil groups at the end of the study. These parameters did not differ between the soybean oil and plant stanol margarine groups. These results suggest that, at the levels tested in the present study, plant stanols provoke hemorrhagic stroke in SHRSP rats to a slightly greater extent than plant sterols. The results also suggest that the mechanism by which plant stanols shorten the life span of SHRSP rat might differ from that of plant sterols.     

Respective Hydrolysis and Esterification of Esterified and Free Plant Stanols Occur Rapidly in Human Intestine After Their Duodenal Infusion in Triacyl- or Diacylglycerol

Esterification of dietary phytosterols and glycerols may affect intestinal absorption of cholesterol and non-cholesterol sterols. We infused plant stanol esters in triacylglycerol (TAG) (F1) and diacylglycerol (DG) (F2) oils, and free plant stanols in F1 and F2 (F3) to the duodenum of healthy human subjects and sampled the contents from the proximal jejunum (PJ). Free and ester sterols were analysed from the infusates, and intestinal contents before and after ultracentrifuge separation of oil, micelle and sediment phases. During the 60-cm intestinal passage, over 40% of plant stanol esters were hydrolysed (P < 0.05) but around 30% of the infused free plant stanols (P < 0.05) and up to 40% of cholesterol (P < 0.05) were esterified in PJ after infusions. TAG in F1 favoured accumulation of plant stanol esters in the oil phase of the PJ aspirates as compared with respective values of F2 and F3 (P < 0.05 for both). About one third of free plant stanols of F3 had been esterified (P < 0.05) and 17% precipitated mainly in free form in the PJ aspirates (P < 0.05 compared with F1 and F2). In conclusion, DG- and TAG-oils had no profound superiority over each other as intestinal carriers regarding hydrolysis/esterification of administered plant stanol esters and cholesterol and their partition in oil, micellar and sediment phases in the PJ. The unesterified plant stanols experienced partial esterification and sedimentation during their intestinal passage, which might influence their biochemical properties in that segment of the gut where cholesterol is absorbed.     

Reduction of processing time by mechanical shaking of the ambient pressure dried TEOS based silica aerogel granules

The present paper deals with preparation of silica aerogel granules by two step acid–base sol–gel process involving ambient pressure drying of alcogels with additional use of mechanical shaker to accelerate the solvent exchange process and characterization of the yielded aerogels granules to study their physical properties. The conventional ambient pressure drying of alcogels is crucial since it needs tedious repetitive gel washing and solvent exchanges (10 times) which consumes total process time of 4 days. We have succeeded to synthesize aerogels within 2 days by making use of alcogels shaking. To get good quality aerogels in terms of low density, high optical transparency, low volume shrinkage, various base catalysts and their combinations were used. The optimal molar ratio of precursor chemicals Tetraethoxysilane (TEOS): Methanol (MeOH): Oxalic acid: NH₄OH: NH₄F: Trimethylchlorosilane (TMCS) found to be 1: 16.5: 0.49: 0.58: 0.60: 0.98, respectively. Among six catalyst studied, combination of NH₄OH and NH₄F resulted in low density and transparent aerogels. Hydrophobicity was achieved by surface silylation using TMCS silylating agent but lead to decrease in transparency due to chloride precipitation. We have improved transparency of aerogels by methanol washing of alcogels prior to silylation. The hydrophobicity has been studied by FTIR analysis and contact angle measurements. The thermal analysis indicates thermal stability of hydrophobicity up to 318 °C and the Surface morphology of aerogel has been studied by FESEM.     

FA determination in cold water marine samples

The determination of FA in cold water marine samples is challenging because of the presence of large proportions of a variety of labile PUFA. This study was undertaken to establish optimal methods for FA analysis in various sample types present in the marine environment. Several techniques used in FA analysis, including lipid fractionation, FAME formation, and picolinyl ester synthesis, were examined. Neutral lipids, acetone-mobile polar lipids, and phospholipids (PL) were readily separated from each other on columns of activated silica gel, but recoveries of PL were reduced. Deactivation of the silica gel with 20% w/w water produced variable recoveries of PL (66±22%). FAME formation with BF₃ gave optimal recoveries, and a method to remove hydrocarbon contamination from these samples before GC analysis using column chromatography was optimized. Picolinyl derivatives of FA are useful in structural determinations with MS, and a new base-catalyzed transesterification method of their synthesis from FAME was developed. Finally, a series of calculations, combining FA proportions with acyl lipid class concentrations, was designed to estimate FA concentrations. In algae and animal samples, these estimates were in good agreement with actual FA concentrations determined by internal standards.     

Acid Precipitation and Purification of Wheat Straw Lignin

ABSTRACT

The acid precipitation and purification of lignin from wheat straw soda pulping effluent were studied. Prior to lignin precipitation, the suspended solids and dissolved silica were removed from the effluent to avoid lignin contamination. Suspended solids and dissolved silica were removed by centrifugation and selective precipitation at pH 5, respectively. After these treatments, the pH of the effluent was reduced to an optimum pH value of 3.5 with sulfuric acid in order to precipitate lignin. About 80% of the total lignin was recovered. Effluent color and COD were simultaneously reduced by 82 and 71%, respectively. Lignin precipitate purification was carried out by washing with aqueous acidic solutions. Only the time and the agitation rate influenced the washing process. The purity of the lignin was very high when the time and rate of agitation during washing were low. Under optimum conditions, lignin with a purity of 99.5% can be obtained.     

Ratio of starting raw material and fluorinating agent in the process of purifying silica-containing raw material

The influence of NH₄HF₂ fluorinating agent on the yield of ammonium hexafluorosilicate intermediate product and amorphous silica in the fine purification of silica-containing raw material by the fluoride technology has been studied. Mixtures with different fluorinating agent contents were investigated by synchronous thermal analysis. The determination of the phases of intermediate products at various ratios of starting silica-containing raw material and NH₄HF₂ was carried out by the X-ray phase analysis method. The optimal ratio of components for the preparation of ammonium hexafluorosilicate and amorphous silica with maximal yield and purity level of the final products was determined.     

An effective separation and purification of rutin and scoparone from Herba Artemisiae Scopariae by solid-phase extraction cartridges packed with an ionic liquid-based silica

Five types of ionic liquid-based silica were synthesized as solid-phase extraction (SPE) sorbents for separation and purification of bioactive compounds, that is, rutin and scoparone extracted from Herba Artemisiae Scopariae. The SilprBImCl material with the highest adsorption capacity was selected as the sorbent for SPE packing. Ethyl acetate and water were found to be suitable washing and eluting solvents, respectively. SilprBImCl was then applied to multi-phase extraction, and its superiority as a sorbent over the commercial cartridge was proven with high rutin and scoparone recoveries of 90.5% and 83.9%, respectively. This highlights the potential of ionic liquid-based silica materials applied to SPE and MPE.     

Characteristics of ammonia permeation through porous silica membranes

A sol–gel method was applied for the preparation of silica membranes with different average pore sizes. Ammonia (NH₃) permeation/separation characteristics of the silica membranes were examined in a wide temperature range (50–400°C) by measurement of both single and binary component separation. The order of gas permeance through the silica membranes, which was independent of membrane average pore size, was as follows: He > H₂ > NH₃ > N₂. These results suggest that, for permeation through silica membranes, the molecular size of NH₃ is larger than that of H₂, despite previous reports that the kinetic diameter of NH₃ is smaller than that of H₂. At high temperatures, there was no effect of NH₃ adsorption on H₂ permeation characteristics, and silica membranes were highly stable in NH₃ at 400°C (i.e., gas permeance remained unchanged). On the other hand, at 50°C NH₃ molecules adsorbed on the silica improved NH₃‐permselectivity by blocking permeation of H₂ molecules without decreasing NH₃ permeance. The maximal NH₃/H₂ permeance ratio obtained during binary component separation was ～30 with an NH₃ permeance of ～10^?7 mol m^?2 s^?1 Pa^?1 at an H₂ permeation activation energy of ～6 kJ mol^?1. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

正交试验优选硅胶洗涤工艺

用正交试验法对硅胶洗涤的工艺进行优选,以杂质洗涤率为指标,选用L9(34)正交试验表进行正交试验。结果表明:硅胶洗涤的最佳工艺条件为液固比(V水∶m硅胶)=3∶1、洗涤温度70℃、洗涤时间2 h,搅拌速率200 r/min。在此条件下洗涤2次,硅胶中95%以上的水溶性杂质被除去。     

DETERMINATION OF THE OPTIMUM PREPARATION CONDITION OF THE SOL-GEL SiO2 USING THE RESPONSE SURFAC METHODOLOGY

A typical sol - gel process consists of the liquid reaction, the solution gelation, and followed by the dehydration. The surface properties of silica gel such as surface area, pore volumes, and the pore diameter were affected by the manufacturing variables including pH values, gelation and dehydration temperatures. The objective of this study is to determine the optimum preparation conditions to maximize a response of surface area, or minimize its pore diameter. In addition, interactions between process variables were studied and their significance to the surface properties was also weighted. It was found that the surface area of silica gels increased with an increasing amount of NH₄OH to a maximum value and then decreased. As a drying temperature kept constant, the surface area and the pore volume increased with an increasing gelation temperature. However, the pore diameter was not influenced by this factor and the pore size was almost uniform at a low NH₄OH concentration. For a higher NH₄OH concentration, the pore volume and the pore diameter became larger but the surface area became smaller as the gelation temperature increased. By means of the response surface methodology analysis, the optimum processing condition was found to be 0.0155 mole of NH₄OH, 80,3°C for gelation temperature, and 63.2°C for the dehydration. As a result the maximum surface area corresponding to the optimum preparation conditions was 818.9 (m²/g) as expected.     

Synthesis of colloidal nanosilica from waste glass powder as a low cost precursor

Waste glass powder was used as a low cost precursor for production of colloidal nanosilica for the first time. The process includes production of wet silica gel and thermal peptization of the wet gel. Purification of the glass powder and wet gel production were initiated by acid washing. The obtained powder was reacted with sodium hydroxide to produce wet silica gel. Type of the applied acid was examined in one factor at a time route. Temperature of the alkaline step and concentrations of the applied acid and base were investigated using Taguchi design of experiments. After finding the best combination of the investigated factor levels in production of the wet gel, time of the stabilization in thermal peptization was studied. Characterizations of the wet gel and colloidal silica were performed by XRF, DLS, FESEM, TEM, FTIR and N₂ sorption evaluation. Accordingly pure and stable colloidal nanosilica (98.50%) with average particle size of 21.9?nm was produced from the glass powder successfully. Specific surface area of the dried porous optimum sample was 83.63?m²/g.     

粪大肠菌群检测方法研究进展

粪大肠菌群是水体粪便污染的指示菌。详细介绍了多管发酵法、滤膜法、纸片法、酶底物法及分子生物学方法检测粪大肠菌群的优缺点及主要应用实例。     

大豆异黄酮的纯化工艺研究

采用大孔吸附树脂、硅胶、葡聚糖凝胶及反相硅胶RP-18等4种填料的柱层析法纯化大豆异黄酮。结果表明,四种层析填料的纯化效果均较好,大豆异黄酮纯度达30％以上,其中以葡聚糖凝胶为填料的柱层析法分离纯化效果最佳,纯度可达55．45％,提取率为90％。     

介孔硅胶负载次氯酸脱除柴油中的硫化物

采取介孔硅胶负载次氯酸脱除硫含量为150μg·g-1的4,6-二甲基二苯并噻吩模型柴油中的硫化物,考察孔结构和脱硫条件对介孔硅胶负载次氯酸脱除模型柴油硫化物的影响,研究再生条件对脱硫剂再生效果的影响。通过红外光谱和N2等温吸附对硅胶进行表征,N2等温吸附分析结果表明,实验选用的3种硅胶均为介孔硅胶;红外光谱分析结果表明,不同孔结构的介孔硅胶均可以负载次氯酸并将模型柴油中4,6-二甲基二苯并噻吩氧化为砜并吸附在介孔硅胶上。SGA型硅胶脱硫率较低;而在反应温度35℃和剂油质量比0.050条件下,使用次氯酸负载质量分数为90.7%的SGB型硅胶,脱硫率达97.3%,使用次氯酸负载质量分数为79%的SGC型硅胶,脱硫率达99.0%。在反应温度30℃和剂液质量比0.19条件下,分别清洗10次,清洗时间5 min,SGC型硅胶的脱硫率下降幅度很小,而SGB型硅胶的脱硫率明显下降。大孔径有利于介孔硅胶负载次氯酸脱除柴油中的硫化物,而且有利于脱硫剂的再生。     

Transparent silica thin films prepared from sodium silicate and bovine serum albumin with petal effect

A variety of advanced functions such as hydrophilicity and hydrophobicity are required for transparent glass plates recently. This paper reports a new procedure to produce transparent silica thin films on glass plates obtained from sodium silicate as inexpensive silica source by its dip coating and subsequent deposition of silica with (NH₄)₂SO₄ solution. When the thin films were prepared using bovine serum albumin (BSA), the resulting transparent films became more hydrophobic than that obtained without BSA and had good adhesion with water droplet, the so-called “petal effect”. Water droplet on the silica thin film did not slide down even when the substrate turned vertically and upside down. Although no BSA was included in the silica thin film, BSA contributed to the formation of nano-sized asperity structures in the film, producing more hydrophobic (less hydrophilic) property and the petal effect.     

Beneficial role of SiO2 plugging in AlCl3 heterogenized plugged hexagonal templated silica (PHTS) for the isopropylation of m-cresol

Plugged hexagonal templated silica (PHTS – a modified SBA-15) has been synthesized using triblock co-polymer as template and tetraethyl orthosilicate as silica source under hydrothermal conditions and AlCl₃ has been heterogenized on it which is proven to be an efficient heterogeneous catalyst for the isopropylation of m-cresol. The activity of AlCl₃ heterogenized on SBA-15 has also been tested for the purpose of comparison. The higher activity of Al–PHTS over Al–SBA-15 has been attributed to the presence of more number of medium strength acid sites formed by the plugging of silica and higher AlCl₃ heterogenization in the former catalyst as observed from ²⁷Al MAS NMR and temperature programmed desorption of NH₃.     

The effects of hydrophilic structures of active carbon on the adsorption of benzene and methanol vapors

Two kinds of commercial coconut-shell active carbons were treated by sequential washing with hydrochloric acid, hydrofluoric acid and water followed by deoxygenation at 1000°C in a H₂ atmosphere. The determination of the hydrophilic structures such as oxygen complexes and ash before and after the treatments showed that these structures covered about 10% and 6% of the surfaces of the original active carbons and decreased to one-tenth or one-fourth after the treatments.Dynamic adsorption of benzene and methanol vapors carried by nitrogen with or without moisture was performed through the beds of those active carbons and a kind of silica gel. The results showed that the removal of hydrophilic structures of the active carbons decreased the adsorption affinities for methanol and water, but not for benzene. Coexistent moisture caused a decrease in the adsorption of benzene, and the effect was greatest on silica gel and smallest on the treated active carbons. It also caused a decrease in the adsorption of methanol by silica gel, but promoted the adsorption of methanol by the active carbons. The removal of hydrophilic structures promoted the selective adsorptivity of active carbon to a hydrophobic adsorbate from a hydrophilic adsorbate.     

磷肥副产硅胶洗涤工艺试验研究

在预试验的基础上,研究了磷肥副产硅胶洗涤的影响因素,利用正交试验优化洗涤条件。采用响应曲面法,建立洗涤效率的回归模型,优化得到最佳洗涤工艺条件。结果表明,硅胶洗涤的最佳工艺条件为液固比10∶1,洗涤时间2 h,搅拌强度400 r/m in。在此条件下,经过5次水洗,磷肥副产硅胶中F、N、P的平均洗涤效率可达86.10%,95%以上水溶性杂质被脱除。     

Ion-exchange and ion-transport in silica and sulphonated-silica (ormosil) hydrogels

The effects of organosulphonate groups on the ion-exchange and ion-transport properties of silica hydrogels have been investigated by using Ru(NH₃)₆³⁺, Ru(bpy)₃²⁺ and Fe(CN)₆³⁻ redox probes. Silica and sulphonated ormosil hydrogels were prepared by using tetramethyl orthosilicate as a silica precursor and 2(4-chlorosulphonylphenyl)ethyl-trichlorosilane to provide sulphonate functionality for ion-exchange and ion conductivity. Both gels act as cation-exchangers and exclude Fe(CN)₆³⁻. Partition coefficients are higher for the ormosil and for the more highly charged Ru(NH₃)₆³⁺ versus Ru(bpy)₃²⁺. Diffusion coefficients are higher for the unmodified silica, which is consistent with weaker interactions between the cationic probes and less anionic gel network.