电感耦合等离子体发射光谱(ICP-OES)法测定橘子汁中钙和镁

建立了微波消解和湿法消解对样品进行前处理,电感耦合等离子体发射光谱法(ICP-OES)测定橘子汁样品中钙和镁含量的方法。选择Ca 317.933nm,Mg 285.213nm作为钙和镁的分析线。实验结果表明,钙和镁的检出限分别为0.001 8和0.000 4mg/L,相对标准偏差(RSD2%),加标回收率为99%~101%,用来测定FAPAS国际比对橘子汁样品,反馈的统计结果显示钙和镁元素的Z值分别为-0.3和0.3,结果均为满意。方法快速、简单、精确,适于橘子汁中钙和镁的测定。     

Biodiesel Production by Single and Mixed Immobilized Lipases Using Waste Cooking Oil

Biodiesel is one of the important biofuels as an alternative to petroleum-based diesel fuels. In the current study, enzymatic transesterification reaction was carried out for the production of biodiesel from waste cooking oil (WCO) and experimental conditions were optimized, in order to reach maximum biodiesel yield. Bacillus stearothermophilus and Staphylococcus aureus lipase enzymes were individually immobilized on CaCO₃ to be used as environmentally friendly catalysts for biodiesel production. The immobilized lipases exhibited better stability than free ones and were almost fully active after 60 days of storage at 4 °C. A significant biodiesel yield of 97.66 ± 0.57% was achieved without any pre-treatment and at 1:6 oil/methanol molar ratio, 1% of the enzyme mixture (a 1:1 ratio mixture of both lipase), 1% water content, after 24 h at 55 °C reaction temperature. The biocatalysts retained 93% of their initial activities after six cycles. The fuel and chemical properties such as the cloud point, viscosity at 40 °C and density at 15 °C of the produced biodiesel complied with international specifications (EN 14214) and, therefore, were comparable to those of other diesels/biodiesels. Interestingly, the resulting biodiesel revealed a linolenic methyl ester content of 0.55 ± 0.02% and an ester content of 97.7 ± 0.21% which is in good agreement with EN14214 requirements. Overall, using mixed CaCO₃-immobilized lipases to obtain an environmentally friendly biodiesel from WCO is a promising and effective alternative for biodiesel production catalysis.     

Continuous Laminaribiose Production Using an Immobilized Bienzymatic System in a Packed Bed Reactor

The first continuous production system of laminaribiose from sucrose and glucose in a bienzymatic reaction is reported in this study. Immobilized laminaribiose phosphorylase and sucrose phosphorylase were used in a packed bed reactor system comprising of a 3-cm glass column at 35 °C with a steady feeding flow rate of 0.1 ml/min. Factors affecting product formation including enzyme ratio, peal concept (both enzymes in one pearl or in separate pearls), and pearl size were studied. An enzyme ratio of 2:1 of laminaribiose phosphorylase (LP) to sucrose phosphorylase (SP) when encapsulated separately in bigger size peals resulted in higher concentration of product. Laminaribiose (0.4 g/(L h)) is produced in the optimized system at steady state. The reaction system proved to be operationally stable throughout 10 days of continuous processing. A half-life time of more than 9 days was observed for both biocatalysts.     

Ethanol Production by Fermentation Using Immobilized Cells of Saccharomyces cerevisiae in Cashew Apple Bagasse

In this work, cashew apple bagasse (CAB) was used for Saccharomyces cerevisiae immobilization. The support was prepared through a treatment with a solution of 3% HCl, and delignification with 2% NaOH was also conducted. Optical micrographs showed that high populations of yeast cells adhered to pre-treated CAB surface. Ten consecutive fermentations of cashew apple juice for ethanol production were carried out using immobilized yeasts. High ethanol productivity was observed from the third fermentation assay until the tenth fermentation. Ethanol concentrations (about 19.82–37.83 g L^?1 in average value) and ethanol productivities (about 3.30–6.31 g L^?1 h^?1) were high and stable, and residual sugar concentrations were low in almost all fermentations (around 3.00 g L^?1) with conversions ranging from 44.80% to 96.50%, showing efficiency (85.30–98.52%) and operational stability of the biocatalyst for ethanol fermentation. Results showed that cashew apple bagasse is an efficient support for cell immobilization aiming at ethanol production.     

Characterization of Laser-Induced Plasma of Water Extracted From Orange Juice

Optical emission of laser-induced plasma on the surface of water extracted from fresh orange juices provides sensitive analysis of trace elements. This emergent technique promises applications with expected outcomes in food security or nutrition quality. Characterization of the plasma induced on such samples can represent a method to characterize the quality of soils where the oranges were planted. In this paper, we present the experimental setup and protocol that optimizes the plasma generation on liquid surfaces. We focus particularly on the detection of Ca, Mg, and Na. By way of stallion solutions (CaCl₂, MgCl₂ and NaCl), we try to determine the concentrations of these elements. We set as samples, oranges coming from Tunisia and Spain.     

Production of Mixed-Linkage Beta-Oligosaccharides from Lichenan Using Immobilized Bacillus licheniformis UEB CF Lichenase

Lichenase from Bacillus licheniformis UEB CF was immobilized on Amberlite IR120 H. The immobilization yield and lichenase activity were 87 and 92.81?% of initial activity, respectively. The immobilized enzyme exhibited a shift in the optimal pH from 5.0 to 3.0, but the activity optimal temperature was not affected. The immobilized enzyme showed a residual activity of 50?% after five uses. It also exhibited high storage stability and retained 50?% of its initial activity after 120?days at 4?°C. The main hydrolysis products yielded from lichenan were trisaccharide and tetrasaccharide. The resulting mixed-linkage beta-oligosaccharides could be used as a special nutriment for lactic bacteria.     

维生素C含量测定实验中果汁试样的保存条件探究

运用库仑滴定法,通过研究室温见光,冷藏避光,充氮除氧和加入EDTA、甲酸、EDTA-甲酸等不同稳定剂后,VC标准溶液和橙汁饮料中VC含量随时间变化的情况,来探究较长时间内储存VC溶液和橙汁饮料的最佳方法.研究表明在冷藏避光条件下向VC标准溶液和橙汁中加入分析实验室常规试剂EDTA作为稳定剂,能保证在1个月内VC的浓度变化在5%以内,可有效避免因VC稳定性引起的实验误差.     

Microbial Fed-batch Production of 1,3-Propanediol Using Raw Glycerol with Suspended and Immobilized Klebsiella pneumoniae

The production of 1,3-propanediol (1,3-PD) was investigated with Klebsiella pneumoniae DSM 4799 using raw glycerol without purification obtained from a biodiesel production process. Fed-batch cultures with suspended cells revealed that 1,3-PD production was more effective when utilizing raw glycerol than pure glycerol (productivity after 47 h of fermentation, 0.84 g?L^?1?h^?1 versus 1.51 g?L^?1?h^?1 with pure and raw glycerol, respectively). In addition, more than 80 g/L of 1,3-PD was produced using raw glycerol; this is the highest 1,3-PD concentration reported thus far for K. pneumoniae using raw glycerol. Repeated fed-batch fermentation with cell immobilization in a fixed-bed reactor was performed to enhance 1,3-PD production. Production of 1,3-PD increased with the cycle number (1.06 g?L^?1?h^?1 versus 1.61 g?L^?1?h^?1 at the first and fourth cycle, respectively) due to successful cell immobilization. During 46 cycles of fed-batch fermentation taking place over 1,460 h, a stable and reproducible 1,3-PD production performance was observed with both pure and raw glycerol. Based on our results, repeated fed batch with immobilized cells is an efficient fermentor configuration, and raw glycerol can be utilized to produce 1,3-PD without inhibitory effects caused by accumulated impurities.     

固相微萃取-气相色谱法测定橙汁中残留有机氯杀虫剂

自制碳纳米管涂层萃取探头,顶空目相微萃取-气相色谱法测定橙汁中有机氯杀虫剂六六六和滴滴涕,优化了影响萃取效率的因素：萃取时间和温度、离子强度、有机溶剂、顶空体积、pH和样品的稀释度等。在0．05～6．0μg·L^-1范围内呈线性关系,方法的检出限在0．003～0．022μg·L^-1之间。该方法用于橙汁样品的测定,对不同的杀虫剂,加标回收率为71．0％～131．0％,相对标准偏差小于10％。     

Characterization and Differentiation of Fresh Orange Juice Variety Based on Conventional Physicochemical Parameters,Flavonoids, and Volatile Compounds Using Chemometrics

The present study focused on the possibility of differentiating fresh-unprocessed orange juice according to botanical origin (variety), based on the use of conventional physico-chemical parameters, flavonoids, and volatile compounds, in combination with chemometrics. For this purpose, oranges from seven different varieties were collected during the harvest years of 2013–2014 and 2014–2015 from central and southern Greece. The physico-chemical parameters that were determined included: electrical conductivity, acidity, pH, and total soluble solids. The flavonoids: hesperidin, neohespseridin, quercetin, naringin, and naringenin were determined using high-performance liquid chromatography (HPLC-DAD). Finally, volatile compounds were determined using headspace solid-phase micro-extraction in combination with gas chromatography-mass spectrometry (HS-SPME/GC-MS). Statistical treatment of data by multivariate techniques showed that orange juice variety had a significant (p < 0.05) impact on the above analytical parameters. The classification rate for the differentiation of orange juice according to orange variety using multivariate analysis of variance (MANOVA) and linear discriminant analysis (LDA) was 89.3%, based on the cross-validation method.     

Physicochemical and Sorption Properties of Silica Gel with Immobilized Xylenol Orange Surface Groups

Organomineral sorbents were prepared by sorption immobilization of Xylenol Orange on the surface of two different samples of silica gel from aqueous solutions with pH 1.68 under static conditions. The diffusion coefficients of Xylenol Organe in the near-surface layer of silica gel and the equilibrium sorption constants were determined. Wash-out of the dye from the sorbent was studied. Sorption of Cu(II), Zn(II), and Pb(II) on the sorbents from aqueous solutions with pH 5.8 was studied.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 1, 2005, pp. 73–78.Original Russian Text Copyright © 2005 by Korneev, Kholin.     

硅烷化衍生-气相色谱-质谱联用法测定橙汁粉中维生素C

橙汁粉样品用N,N-二甲基甲酰胺提取,并离心分离,所得上清液中抗坏血酸与六甲基二硅氨烷和三甲基氯硅烷进行衍生反应,产物用正庚烷萃取。萃取液加入棕榈酸甲酯作为内标,供气相色谱-质谱分析。在气相色谱分离中用HP-5MS毛细管柱(30 m×250μm,0.25μm)为固定相,在质谱测定中采用全扫描模式。硅烷化抗坏血酸标准与内标峰面积的比值与硅烷化抗坏血酸的质量在1.0～5.0 mg范围内呈线性关系。方法用于橙汁粉样品中维生素C的测定,橙汁粉中维生素C的平均质量分数(n=6)为0.195 4%,回收率在92.3%～98.5%之间。     

Production of Ethanol from Sweet Sorghum Juice Using VHG Technology: A Simulation Case Study

The aims of this study were to develop the kinetic model and determine kinetic parameters describing ethanol production from sweet sorghum juice using very high gravity technology in the batch fermentation of Saccharomyces cerevisiae NP01. The obtained experimental data were tested with four different types of model, based on the experimental data, accounting for the substrate limitation, substrate inhibition, product inhibition, and the combination of those three effects, respectively. The optimization technique to find kinetic parameters was non-linear regression using Marquardt method performed through numerical procedure. The chosen model with its kinetic parameters obtained in the batch mode was validated and tested against the other independent experimental data in the small batch-scale and large-scale fermenter, in order to investigate the applicability and scale-up effect of the model, respectively. Then, the obtained model with its parameters was applied in the simulations of the continuous and fed-batch operations to examine the concentration profiles of fermentation components with the variations in operating parameters such as the dilution rate, feed-flow rate, start-up time, and feed concentration. The results indicated that the kinetic model (the substrate limitation with substrate and product inhibition effects) was suitable to describe ethanol fermentation. In the continuous mode, using the dilution rate of 0.01 h^?1, the maximum ethanol concentration obtained was, approximately, 90 g/l whereas the simulated results from the fed-batch operation revealed that the maximum ethanol concentration at quasi-steady state condition was, approximately, 96 g/l. The start-up time of 21 h was the fastest time to reach the steady-state and quasi-steady state for both the continuous and fed-batch modes, respectively.     

Test Determination of Lead and Zinc in Water with the Use of Xylenol Orange Immobilized on Silica

Xylenol Orange immobilized on silica as a complex of iron(III) was used for the test determination of lead(II) and zinc(II) in drinking water over concentration ranges of 10–100 and 13–130 g/L, respectively. The maximum distribution coefficients were found to be 7.50 × 10³ mL/g for Pb and 3.75 × 10³ mL/g for Zn. The macro main trace components of water at a level of their maximum permissible concentrations caused no interference. Al(III), Fe(III), and Zn(II) in the presence of NH₄F did not interfere with the determination of Pb(II), whereas lead in the presence of acetate caused no interference with the determination of Zn(II).     

Exploring the Influence of Intermolecular Interactions in Prebiotic Chemistry Using Laser Spectroscopy and Calculations

One of the most fascinating questions in chemistry is why nature chose CGAT as the alphabet of life. Very likely, such selection was the result of multiple factors and a long period of refinement. Here, we explore how the intermolecular interactions influenced such process, by characterizing the formation of dimers between adenine, theobromine and 4-aminopyrimidine. Using a combination of mass-resolved excitation spectroscopy and DFT calculations, we determined the structure of adenine-theobromine and 4-aminopyrimidine-theobromine dimers. The binding energy of these dimers is very close to the canonical adenine-thymine nucleobases. Likewise, the dimers are able to adopt Watson-Crick conformations. These findings seem to indicate that there were many options available to build the first versions of the informational polymers, which also had to compete with other molecules, such as 4-aminopyrimidine, which does not have a valid attaching point for a saccharide. For some reason, nature did not select the most strongly-bonded partners or if it did, such proto-bases were later replaced by the nowadays canonical CGAT.     

A Novel and Efficient Production of Amines from Azides Using LiCl/NaBH4

A practical & efficient reagent system LiCl/NaBH₄ is used for the production of amines from azides is described.     

Stability and Rheological Properties of Suspended Pulp Particles Containing Orange Juice Stabilized by Gellan Gum

Gellan was used to suspend pulp particles in orange juice. Three groups of samples were prepared with 0%, 20%, and 40% orange juice concentrate and supplemented with gellan at different concentrations. A concentration-dependent increase in the size of gellan aggregates and gellan-protein assemblies was observed. Incorporation of gellan into the beverage with 0% juice concentrate changed the rheological behavior of sample to non-Newtonian shear-thinning fluid and increased its surface tension. When juice concentrate proportion was increased from 0% to 20%, the beverage viscosity increased. The highest gellan concentration resulted in a higher yield stress (σ₀) value and inhibited the pulp sedimentation completely.      

Glucose Biosensor Using Glucose Oxidase Immobilized in Polyaniline

A biosensor for glucose utilizing kinetics of glucose oxidase (EC 1.1.3.4.) was developed. The enzyme was immobilized on polyaniline by covalent bonding, using glutaraldehyde as a bifunctional agent. The system showed a linear response up to 2.2 mM of glucose with a response time of 2.5–4.0 min. In addition, the immobilized enzyme had a higher activity between pH 6.5 and 7.5. The system retained 50% of its activity after 30 d of daily use. The optical absorption spectra of the polyaniline/glucose oxidase electrode after glucose had been added to the buffer solution showed that the absorption band around 800 nm had changed considerably when glucose was allowed to react with the electrode. This optical variation makes polyaniline a very promising polymer for use as a support in optical sensor for clinical application.     

Characterization and Semiquantitative Analysis of Volatile Compounds in Orange Juice by Use of Headspace-Solvent Microextraction and Gas Chromatography

By alternate use of two different extraction solvents, n-hexadecane and benzyl alcohol, a headspace-solvent microextraction (HSME)–GC–FID/MS method has been established for characterization of the volatile components of an orange juice beverage. The method avoids two disadvantages of conventional HSME—difficulty identifying components obscured by the solvent peak and inefficient extraction of some of the compounds if one solvent only is used. The optimum conditions (droplet volume, equilibration temperature and time, extraction time, and ionic strength) were determined by the factor-rotation method. The volatile components of the beverage were mainly terpenes, terpenols, fatty acids, and alcohols, for example limonene (114.71 mg L⁻¹), phellandrene (4.50 mg L⁻¹), terpineol (p-menth-1-en-8-ol; 3.12 mg L⁻¹), α-pinene (0.33 mg L⁻¹), n-hexadecanoic acid (0.28 mg L⁻¹), and terpinol (0.13 mg L⁻¹).