Effects of processing on oxidative stability of sesame oil extracted from intact and dehulled seeds

Oxidative stability of oils extracted from intact and dehulled sesame seeds was determined by monitoring changes in fatty acid composition, iodine value (IV), peroxide value (PV), conjugated diene (CD), para-anisidine value (p-AV), and 2-thiobarbituric acid (TBA) value and by nuclear magnetic resonance spectroscopy after storage under Schaal oven conditions at 65°C for up to 35 d. The oils from coated seeds were more stable, as reflected in PV, CD, p-AV and TBA values, than those extracted from dehulled seeds after roasting at 200°C, steaming at 100°C, roasting at 200°C plus steaming, or microwaving at 2450 MHz, except for TBA values of oil from microwaved seeds. After 35 d of storage at 65°C, the CD, p-AV, and TBA values of extracted oil from dehulled microwaved seeds were 17.72, 10.20, and 1.22, respectively, while those of their coated counterparts were significantly (P<0.05) different at 14.20, 16.47, and 1.26, respectively. Few significant changes were evident in the fatty acid composition of oil obtained from either coated and dehulled seeds subjected to different treatments. Nuclear magnetic resonance analyses found that R_ao (aliphatic to olefinic protons) and R_ad (aliphatic to diallylmethylene protons) ratios increased steadily over the entire storage period, which indicated progressive oxidation of unsaturated fatty acids.     

Fate of minor free amino acids and phospholipids in crude tallow during steam splitting

Minor free amino acids and phospholipids contained in crude tallow were monitored during steam splitting of crude tallow. The bulk of the phospholipids was found in the glycerol sidestream after splitting. Phosphatidic acid and phosphatidylcholine were present in both crude tallow and the glycerol fraction. Phosphatidylserine and phosphatidylethanolamine present in crude tallow were hydrolized with the glycerides. Because of this hydrolysis, high amounts of serine and ethanolamine are found in the fatty acid and glycerol fractions. In addition to constituent amino acids of proteins present in crude tallow, other biological amino acids such as taurine and ornithine were also present.     

氨基酸分离提纯的研究进展

本文对氨基酸分离提纯常用的沉淀法、离子交换法、萃取法、吸附法等方法的原理及研究进展状况作了较全面的总结。     

硅酸盐色谱分离中性氨基酸性能研究

将硅酸钠与硫酸铜或硫酸锌按等体积混合 ,制得新型无机离子交换剂硅酸铜、硅酸锌 ,分别用其作为色谱载体对中性氨基酸 (甘氨酸 ,丙氨酸 )进行分离 ,与强酸性阳离子交换树脂 0 0 1× 7的色谱行为作了比较。结果表明 ,合成的硅酸盐具有较好的分离性能。通过不同载体分离中性氨基酸 (甘氨酸 ,丙氨酸 )的流出体积的比较 ,硅酸铜的流出体积大于硅酸锌 ,硅酸锌的流出体积大于 0 0 1× 7。结果显示 ,硅酸铜比硅酸锌更适合于分离中性氨基酸 ,具有最好的分离特性     

Separation and identification of amino acids from lignite humic acids by thin layer chromatography

Thin layer chromatography with and without temperature gradient was used to identify ten amino acids in the humic acid hydrolysate of Rovinari lignite, using cellulose and volcanic tuff as stationary phases. The acids found were L-leucine, isoleucine, phenylalanine, L-valine, tyrosine, proline, L-alanine, glutamic acid, threonine and L-lysine.     

Enantioselective separation of basic amino acids on talc

Certain amino acid derivatives (ε-basic, anilide group) can be readily adsorbed onto various types of talc (steopac, SS20, C300, C400). For instance, talc is capable of adsorbing the amino acid esters but not the equivalent free amino acids. The types of talc which have high hydrophobicity (00, 15M00) were poor adsorbents. Two applications of these findings are presented: enhancement of the sensitivity of enzymatic tests in the presence of chromogenic substrates and enantioselective separation of ε-basic amino acids (arginine, lysine, ornithine).     

Effect of addition of amino acids on microfiltration behavior of a microorganism slurry

The effect of the addition of amino acids on the microfiltration behavior of Escherichia coli (E coli) and Corynebacterium glutamicum (C glutamicum) slurry was examined using a dead‐end microfilter. It was found that the average specific filtration resistance, α_av, of a slurry of microorganisms increased markedly by adding amino acids. Amino acid concentration ranged from 110 to 876 mol m^?3. However the same concentration of ammonium chloride did not increase α_av. The cells were found to disperse in the presence of lysine, and this caused an increase in α_av. In the case of kaolin slurry, α_av was not affected by adding amino acids. Copyright © 2004 Society of Chemical Industry     

Processing of N-terminal unnatural amino acids in recombinant human interferon-beta in Escherichia coli

Incorporation of unnatural amino acids into recombinant proteins represents a powerful tool for protein engineering and protein therapeutic development. While the processing of the N-terminal methionine (Met) residues in proteins is well studied, the processing of unnatural amino acids used for replacing the N-terminal Met remains largely unknown. Here we report the effects of the penultimate residue (the residue after the initiator Met) on the processing of two unnatural amino acids, L-azidohomoalanine (AHA) and L-homopropargylglycine (HPG), at the N terminus of recombinant human interferon-beta in E. coli. We have identified specific amino acids at the penultimate position that can be used to efficiently retain or remove N-terminal AHA or HPG. Retention of N-terminal AHA or HPG can be achieved by choosing amino acids with large side chains (such as Gln, Glu, and His) at the penultimate position, while Ala can be selected for the removal of N-terminal AHA or HPG. Incomplete processing of N-terminal AHA and HPG (in terms of both deformylation and cleavage) was observed with Gly or Ser at the penultimate position.     

Potential-controlled chromatography for the separation of amino acids and peptides

Potential-controlled chromatography is introduced as a new technique for the separation of amino acids and peptides. The principle of potential-controlled chromatography depends on the use of electrically conductive material as the stationary phase of the chromatographic column. Thus from an electrochemical point of view the packed column can be regarded as a packed-bed electrode. The electrical potential of this stationary phase can be controlled by a potentiostat. The separation of amino acid and peptide molecules during their migration through the column depends on their own electric charge on the one hand and on the electrical potential of the stationary phase on the other. The chromatographic separation of some amino acids could be demonstrated.     

Removal of amino acids from water by adsorption on polystyrene resins

The adsorption of eight amino acids, L ‐asparagine, D,L ‐threonine, L ‐lysine, L ‐leucine D,L ‐methionine, L ‐tyrosine, L ‐phenylalanine and D,L ‐tryptophan, on the non‐polar macroporous adsorbents Amberlite XAD‐2 and XAD‐4 (polystyrene–divinylbenzene copolymers) was studied. Equilibrium adsorption experiments were conducted to estimate the types of isotherm and their parameters. The effect the chemical composition and structure of the amino acids on the efficiency of adsorption was evaluated. The influence of pH and ionic strength was also studied. The data of adsorption isotherms of the examined amino acids seemed generally to approach the Freundlich isotherm model. Tryptophan isotherm adsorption data could match in some cases the Langmuir model. The majority of the adsorption isotherms were almost linear. In terms of adsorbed amino acid on both resin surfaces, the amino acids can be ranked thus: D,L ‐tryptophan > L ‐phenylalanine > D,L ‐methionine, L ‐tyrosine > L ‐leucine > L ‐lysine > D,L ‐threonine > L ‐asparagine. In low pH solution, adsorption was generally higher than that at intermediate and high pH values. Generally, as the ionic strength increases, the adsorption of the amino acids increases. © 2001 Society of Chemical Industry     

Adsorption equilibrium of amino acids and antibiotics on non‐ionic polymeric sorbents

Adsorption equilibria of two amino acids (phenylalanine and tryptophan) and two antibiotics (penicillin G and cephalosporin C) from aqueous solutions onto non‐ionic polymeric sorbents (XAD‐4 and XAD‐16) were investigated under various experimental conditions such as pH, temperature and organic solvents. The assumption that amino acids adsorbed on polymeric sorbents were desorbed by competitive adsorption with organic solvent as a desorbate was verified using binary adsorption data for amino acids (phenylalanine and tryptophan) and organic solvents (isopropyl alcohol and methanol) on XAD‐4 and XAD‐16. The experimental data were predicted by using multicomponent adsorption models of an Extended‐Langmuir (EL) equation and an ideal adsorbed solution theory (IAST) based on the Langmuir equation as a single‐component isotherm. Copyright © 2004 Society of Chemical Industry     

电驱动膜过程在氨基酸发酵液处理中的研究进展

在发酵法生产氨基酸的过程中,需要后续工艺对发酵液进行分离纯化以提取目标产物.电驱动膜过程正逐渐成为该领域研究与应用的热点.本文介绍了近年来国内外普通电渗析(ED)、双极膜电渗析(BMED)、离子取代电渗析(ISED)、电复分解反应器(BMT)等常见的电驱动膜过程在氨基酸发酵液处理中的研究进展,简述了常见的膜堆构型及其工作原理、特点与应用实例.分析表明电驱动膜过程可以实现混合氨基酸分离、无机盐脱除以及氨基酸的制备,膜堆结构、操作参数的优化以及新型分离膜的研究与应用可以提高过程性能.同时也指出目前该领域的研究尚处于实验室研究阶段,研究对象以模拟发酵液为主,规模化应用的报道还不多见.但是可以预见高效、环保的电驱动膜过程将会在氨基酸发酵液处理中发挥重要作用.     

Effect of processing and amino acids supplementation on the protein quality of amaranth (Amaranthus caudatus)

The present study was undertaken to evaluate the effect of thermic processing on the protein quality of amaranth (A. caudatus). It was also intended to establish the order of essential amino acid deficiencies suggested by the chemical score as limiting protein quality. The A. caudatus grain was cooked in water in the autoclave at 15 lb pressure during 0, 10, 20, 30, 40, 50 and 60 min. Once cooked, the samples were dehydrated with hot air at 60 degrees C and ground into flours. These were analyzed for: tannins, trypsin inhibitors, hemagglutinins (with cow, sheep, and human erythrocytes), damaged starch, available lysine, protein quality (by the NPR method), and true digestibility. Results indicated that the flours (0 to 60 min cooked) did not contain trypsin inhibitors and that their small tannin content, expressed as catechin, disappeared after 30 min of cooking. The quantities of these antiphysiological substances in the raw material are so small that they do not constitute a factor that may cause a decrease of the product's quality. A positive response was obtained for hemagglutinins, stronger with human erythrocytes, which disappeared with cow's and sheep's erythrocytes after 10 min of cooking and with human erythrocytes, after 20 min. As expected, cooking time increased the damaged starch and a slight increase was observed in available lysine, a finding which was impossible to explain satisfactorily. There were no important changes in true protein digestibility with respect to cooking time. Once again, results demonstrated the positive effect thermic treatment had on protein quality, suggesting the presence of antiphysiological active substances or a low nutrient bioavailability in raw samples. Longer cooking times did not alter substantially the protein quality (NPR and digestibility) and it was concluded that 10 min of cooking is an adequate time for the type of processing used. A sample of processed A. caudatus was utilized for the supplementation studies carried out with threonine, methionine, leucine, individually, or with the three amino acids together at 8.0, 9.5 and 1.0% protein in the diet. According to the results obtained, higher NPR values were observed with 9.0 and 9.5% protein content in the diet. No clear effects were detected when the amino acids were added, but there was an interaction between protein in the diet and amino acids. No effect occurred when leucine was added, suggesting that it is not a limiting amino acid. Possibly, threonine is a more limiting amino acid, but the effects were not as high, probably due to the level added to the diets.(ABSTRACT TRUNCATED AT 400 WORDS)     

Black sesame (Sesamum indicum L.) seeds extracts by CO2 supercritical fluid extraction: Isotherms of global yield,kinetics data,total fatty acids,phytosterols and neuroprotective effects

In Brazilian folk medicine, black sesame (Sesamum indicum L.) seeds are one of the most important ingredients present in the tea used to treat stroke victims. Nevertheless, extracts by supercritical extraction of black sesame seeds have not been applied in neuroprotection studies. The objective of this work was to investigate some process variables of supercritical fluid extraction in black sesame to generate extracts applicable in stroke research. Two isothermal (40 and 60 °C) were explored, combined with pressures that ranged from 200 to 400 bar, at a constant mass flow rate of 5.9 × 10⁻⁵ kg/s. The global yields ranged from 37 to 53% in dry basis. The highest mass yield was obtained at 60 °C and 400 bar. The fatty acid composition comprised a high unsaturated/saturated ratio. Chromatographic analysis of phytosterol content in the high global yield extract revealed higher amounts of β-sitosterol + sitostanol, cholesterol, campesterol + campestanol + 24-methylene cholesterol, Δ-5 avenasterol and stigmasterol, while lower levels of Δ-5,24 stigmastadienol, brassicasterol, clerosterol + Δ-5-23 stigmastadienol, Δ-7 avenasterol, eritrodiol and Δ-7 stigmasterol were present in the black sesame extract. Overall extraction curves from the supercritical fluid extraction (SFE) in lower and higher global yields (200 and 400 bar at 60 °C) fitted the Tan and Liou, Goto et al. and Sovová models. These models presented the best residual sum of squares values. Pilot experiments suggest that black sesame extract is neuroprotective following endothelin-1-induced focal ischemia into the motor cortex of adult male rat, observing a decrease in leukocyte infiltration in the group treated with SFE of black sesame seeds when compared with control group.     

Intracellular uptake and inhibitory activity of aromatic fluorinated amino acids in human breast cancer cells

Nonproteinogenic amino acids that either occur naturally or are synthesized chemically are becoming important tools in modern drug discovery. In this context, fluorinated amino acids have great potential in the development of novel pharmaceuticals and drugs. To assess whether different fluorinated aromatic amino acid analogues of phenylalanine, tyrosine, and tryptophan are potentially interesting as therapeutic drugs, we examined their cytostatic and cytotoxic effects on the growth of the human breast cancer cell line MCF-7. Of all the tested analogues L-4-fluorotryptophan, L-6-fluorotryptophan and L-p-fluorophenylalanine effectively and irreversibly inhibited cell growth with IC(50) values in the low micromolar range (3-15 microM). Additionally, using L-4-[14C]fluorotryptophan, and L-6-[14C]fluorotryptophan, we discovered that the cellular uptake of these fluorinated amino acids occurs through active transport with a 70-fold excess of intracellular over extracellular concentrations. We identified system L as the responsible amino acid transporter. Our findings fully support the idea that fluorinated aromatic amino acid analogues are promising chemotherapeutics with the potential for use in combination with classical cancer therapy, and as new cytotoxic drugs for certain tumor types such as melanoma.     

离子液体作薄层色谱添加剂对氨基酸分离的研究

将1-丁基-3-甲基咪唑基四氟硼酸盐([Bmim]BF4)离子液体作为薄层色谱展开剂添加剂,讨论了[Bmim]BF4浓度对精氨酸和赖氨酸两种碱性氨基酸分离的影响.结果表明:添加离子液体能有效改善碱性氨基酸的展开效果,而且分析物的Rf值随离子液体浓度的增加而增加,浓度增加到一定后Rf保持不变.另外,比较了[Bmim]PF...     

Enantiomerically pure tetrahydroisoquinolines from the gold-catalysed isomerization of substrates derived from furans and amino acids

A new route to enantiomerically pure 8-hydroxytetrahydroisoquinolines is based on furan derivatives and amino acids from renewable resources and gold catalysis. The stereogenic centre from the amino acid remains unchanged in the product.