Effect of ionic strength on the foam fractionation of BSA with existence of antifoaming agent

Foam fractionation is an economical and effective technology for protein concentration and separation. However, the presence of antifoaming agent in the fermentation broth restricts the application of this technology. In this paper surfactant-assisted foam process was conducted with a mimic system using bovine serum albumin (BSA) as target protein, polyoxypropylene polyoxyethylene glylerin ether (PGE) as antifoaming agent and cetyltrimethyl ammonium bromide (CTAB) as surfactant, putting emphasis on study of the effect of ionic strength on the separation process. The experimental results showed that with ionic strength increasing, the mixed-system foaming ability gradually increased. Under the conditions of C_BSA 100 mg/L, C_CTAB 20 mg/L, C_PGE 8 mg/L and pH 7.4, feed liquid 250 mL, air flow rate 100 mL/min at 25 °C, the maximum enrichment ratio of BSA reached 27 when the ionic strength was 0.0500 mol/kg and the maximum recovery of BSA reached 80.5% when the ionic strength was 0.1696 mol/kg. Furthermore, K⁺ had better separate efficiency than Na⁺ under the same ionic strength.     

Effect of solubilized amines on the structural transition of cetyltrimethylammonium bromide micelles in aqueous potassium bromide

Rod-shaped micelles were produced by mixing 0.1 M cetyltrimethylammonium bromide (CTAB) and 0.1 M KBr in aqueous solution. The effects of the addition of aliphaticn-amines (C₄, C₆, C₇ and C₈) and temperature on the shape of micelles were studied by viscosity measurements. The viscosity data show that transition of rod-shaped micelles to larger aggregates is induced by addition of higher amines (≥C₆) up to a certain concentration; a further increase in concentration produced the opposite effect. Addition of C₄-amine induces only a rod-to-sphere transition. The data were interpreted in terms of solubilization/incorporation (decrease of micellar surface charge density) of amines inside the micelles and the nature of the effective solvent (water+amine). The latter effect dominated the change from larger aggregates to smaller micelles at higher concentrations of the added amine. Increasing the temperature produced effects similar to C₄-amine addition, namely, rod-to-sphere transition. Activation free energy (ΔG^*) and enthalpy (ΔH^*) were also computed from the temperature dependence of the viscosity. ΔG^* and ΔH^* values were higher for larger aggregates (long rods) than for smaller ones (spherical micelles) and ΔH^* covered almost the total contribution to ΔG^*.     

Phosphatidylglycerol molecular species of photosynthetic membranes analyzed by high-performance liquid chromatography: Theoretical considerations

A reversed-phase high-performance liquid chromatography technique was developed to separate, identify, and quantify individual phsphatidylglycerol (PG) molecular species in thylakoid membranes isolated from higher plant leaves. PG was first separated by thin-layer chromatography; then the dinitrobenzoyl derivatives of diacylglycerols produced after phospholipase C hydrolysis of PG were separated by a C₁₈ reversed-phase column and detected at 254 nm. A linear response of the detector was observed in the range of 0.025 to 12 nmol of PG molecular species. It was established that there was an excellent correlation (r=0.996) between the carbon and double-bond number in the aliphatic residues and the relative retention time of dinitrobenzoyl derivatives. A new equivalent carbon number value (ECN^*) which takes into consideration the number ofcis-(n _c ) andtrans-(n _t ) double bonds per molecular species was defined as ECN^*=CN-2n _c -n _t′ where CN is the number of carbon atoms in the aliphatic residues. The logarithm of the retention time increased linearily as a function of ECN^* value. However, in this type of correlation, it may happen that two molecular species of PG having distinct relative retention times has the same ECN^* value. In this case, the two molecular species can be identified by the linear correlation (r=1) existing between the reciprocal of the relative retention time and the number of double bonds (0≤n≤3) in the separate 18:n/Δ3-trans-hexadecenoic acid [16:1(3t) and 18:n/16:0 molecular species series. The advantages of this method are good separation, short elution time, quantitative precision, and predictable retention times of PG molecular species from chloroplast membranes. The method has been used routinely to identify the ten PG molecular species of thylakoid membranes in squash, potato, lettuce, and spinach leaf: 18:3/16:1(3t), 18:3/16:0, 18:2/16:1(3t), 18:2/16:0, 18:1/16:1(3t), 18:1/16:0, 18:0/16:1(3t), 18:0/16:0, 16:0/16:1(3t), and 16:0/16:0.     

An efficient method for a numerical description of virgin olive oil color with only two absorbance measurements

Four polynomial expressions are obtained that provide a good approximation and an easy, rapid calculation of the chromatic coordinates and the chroma—L ^*, a ^*, b ^*, and C—for the illuminant C and the standard observer, for a virgin or extra virgin olive oil; absorbance is measured at only 480 and 670 nm. These are as follows: L ^*=0.556458(A₄₈₀)²−2.51145A₄₈₀+0.55504(A₆₇₀)²−8.53016A₆₇₀+98.4089; a ^*=0.177372(A₄₈₀)²+2.1363A₄₈₀+1.43254(A₆₇₀)²−0.789231A₆₇₀−13.9246; b ^*=−16.0277(A₄₈₀)²+79.8932A₄₈₀−5.06558(A₆₇₀)²+3.36169A₆₇₀+31.9405; C=−15.8439(A₄₈₀)²+78.9312A₄₈₀−5.26784(A₆₇₀)²+3.56917A₆₇₀+33.3927. These give acceptable results, making the method a practical alternative to the extremely laborious Commission Internationale d’Eclairage (CIE) L ^* a ^* b ^* system, by which 391 absorbance values must be measured individually, nanometer by nanometer, before applying more complex equations. The validity of the proposed method has been confirmed by comparison, using a set of 20 sample oils different from the set of 25 oils used to generate the order of the equations. The variations between the values provided by the proposed and standard methods, respectively, had a mean of 0.00 for each of the chromatic variables—L ^* , a ^* , b ^* , and C; SD were moderate (0.71, 0.52, 1.22, and 1.22, respectively); the root mean square and the R ²-terms also confirmed the validity of the method.     

Komplexbildung von geradkettigen Polyolen in wäßriger Lösung mit partiell hydratisierten K+ -und Ca2+ -Ionen in X- und Y-Zeolithen

Complex Formation of Straight-Chain Polyols in Aqueous Solution with Incompletely Hydrated K⁺ and Ca²⁺ Cations on X and Y Zeolites A systematic study was performed on the adsorption of alditole-water mixture with a chain length of C₃ to C₆ on KX, KY and Ca(83)NaY zeolites. From the adsorption excess isotherms the separation factors and the equilibrium diagrams x_s vs x₁ of the binary mixtures were calculated. The possible triangles of 0 atoms of polyols and the influence of the conformation on formation of adsorption complexes are discussed.     

Dynamic and equilibrium surface tensions of surfactin aqueous solutions

A homologous series of surfactins containing β-hydroxy fatty acids having 13, 14, or 15 carbon atoms were isolated from the supernatant of Bacillus subtilis strain S499 cultures. Their surface-active properties at the air-water interface were then evaluated. Dynamic surface tension data were analyzed by the relaxation function γ_t=γ_m+(γ_o−γ_m)/[1+(t/t^*)ⁿ]. Based on various parameters t^*, n, v_max, γ_m calculated from this equation, the dynamic surface properties of surfactin were found to depend on both bulk concentration and hydrophobic character of the alkyl chain. At low concentrations of surfactin, the dynamic surface tension (γ_d) decreased with increasing carbon atom number of the surfactin alkyl chain (n=13 to 15). However, at high concentrations, the maximum decrease of 41-4 was achieved by surfactin-C₁₄. In contrast, more strongly hydrophobic alkyl chains in surfactins always enhanced their ability in reducing the equilibrium surface tensions and their aptitude in forming micelles.     

Stable Carbon Isotope Composition of c9,t11-Conjugated Linoleic Acid in Cow’s Milk as Related to Dietary Fatty Acids

This study explores the potential use of stable carbon isotope ratios (δ¹³C) of single fatty acids (FA) as tracers for the transformation of FA from diet to milk, with focus on the metabolic origin of c9,t11-18:2. For this purpose, dairy cows were fed diets based exclusively on C₃ and C₄ plants. The FA in milk and feed were fractionated by silver-ion thin-layer chromatography and analyzed for their δ¹³C values. Mean δ¹³C values of FA from C₃ milk were lower compared to those from C₄ milk (−30.1‰ vs. −24.9‰, respectively). In both groups the most negative δ¹³C values of all FA analyzed were measured for c9,t11-18:2 (C₃ milk = −37.0 ± 2.7‰; C₄ milk −31.4 ± 1.4‰). Compared to the dietary precursors 18:2n-6 and 18:3n-3, no significant ¹³C-depletion was measured in t11-18:1. This suggests that the δ¹³C-change in c9,t11-18:2 did not originate from the microbial biohydrogenation in the rumen, but most probably from endogenous desaturation of t11-18:1. It appears that the natural δ¹³C differences in some dietary FA are at least partly preserved in milk FA. Therefore, carbon isotope analyses of individual FA could be useful for studying metabolic transformation processes in ruminants.     

Dissolution and enzymatic hydrolysis of casein micelles studied by dynamic light scattering

The effects of temperature, ionic strength, and enzymatic hydrolysis on the average hydrodynamic radius (R _h) of casein micelles in phosphate buffer were studied by using dynamic light scattering. The results showed that the average R _h value of casein micelles decreased irreversibly during the heating, decreased with the increase of ionic strength in lower ionic strength solution (less than 0.05 mol/L), but opposite in higher ionic strength solution (above 0.1 mol/L). The R _h value of casein increased rapidly during the process of enzymatic hydrolysis, and the structural model of casein micelles in the enzymatic hydrolysis process was also proposed, i.e. the casein micelle changed from compact sphere into unfolded and regularly flocky peptides. Translated from The Chinese Journal of Process Engineering, 2006, 6(4), 615–618 [译自: 过程工程学报]     

Pervaporation separation of benzene/cyclohexane through AAOM-ionic liquids/polyurethane membranes

Supported ionic liquids/polyurethane (PU) membranes were prepared by immobilizing ionic liquids on a porous anodic aluminum oxide membrane (AAOM) support that was coated on one side with polyurethane (PU). The microstructure of all membranes was characterized using scanning electron microscopy (SEM). The pervaporation separation performance of the supported ionic liquids/polyurethane membranes was investigated for benzene/cyclohexane (Bz/Cy) mixtures. The SEM results demonstrated that the porous surface of the AAOM support was sealed by the dense polyurethane membrane and the pores of the AAOM support were impregnate with ionic liquids. The ionic liquids filling in the AAOM support enhanced the separation selectivity of Bz/Cy. The separation factor of Bz to Cy increased from 5 to 34.4 and the largest PSI of AAOM-[C₄mim]PF₆/PU membrane reached 452.54 g m⁻² h⁻¹ at 55 °C for a 50 wt.% Bz/Cy mixture. Because the polyurethane prevented the leakage of ionic liquids filled in the AAOM support, the supported ionic liquids/polyurethane membranes exhibited excellent stability.     

Isolation and characterization of the monounsaturated long chain fatty acids ofMycobacterium tuberculosis

The positions of double bond in the monounsaturated C₁₅−C₃₂ fatty acids ofMycobacterium tuberculosis H37Ra were established by gas chromatography/mass spectrometry of the ozonized esters and their pyrrolidide derivatives. The monounsaturated C₁₅−C₂₁ fatty acids had the double bond primarily at the Δ⁹ position while the monounsaturated longer chain fatty acids (C₂₂−C₃₂) had the double bond in several positions. Many of the latter acids, especially the odd-numbered series, were very complex isomeric mixtures. Quantitation showed the most abundant even-numbered long chain fatty acid isomers to be as follow: C₂₂, Δ⁴; C₂₄, Δ⁵; C₂₆, Δ⁷ and Δ⁹; C₂₈, Δ⁹; C₃₀, Δ¹¹ and Δ¹³; C₃₂, Δ¹³ and Δ¹⁵.     

Cycloaddition of carbon dioxide to epichlorohydrin using ionic liquid as a catalyst

The cycloaddition of carbon dioxide to epichlorohydrin was performed without any solvent in the presence of ionic liquid as catalyst. 1-Alkyl-3-methyl imidazolium salts of different alkyl group (C₂, C₄, C₆, C₈) and anions (Cl⁻, BF₄⁻, Br⁻, PF₆⁻) were used for this reaction carried out in a batch autoclave reactor. The conversion of epichlorohydrin was affected by the structure of the imidazolium salt ionic liquid; the one with the cation of longer alkyl chain length and with more nucleophilic anion showed better reactivity. The conversion of epichlorohydrin increased as the temperature increased from 60°C to 140°C. It also increased with increasing carbon dioxide pressure probably due to the increase of the absorption of carbon dioxide into the mixture of epichlorohydrin and the ionic liquid. Zinc bromide was also tested for its use as a cocatalyst in this reaction. This work was presented at the 6 ^th Korea-China Workshop on Clean Energy Technology held at Busan, Korea, July 4–7, 2006.     

Preparation of microporous silica membranes for gas separation

Microporous silica membranes for hydrogen separation were prepared on a γ-alumina coated α-alumina tube by sol-gel method. The reactants of sol-gel chemistry were tetraethoxysilane (TEOS) and methacryloxypropyl-trimethoxysilane (MOTMS). The silane coupling agent, MOTMS, was added as a template in order to control the pore structure to the silicon alkoxide, TEOS. In particular, the microporous membranes were prepared by changing the molar ratio of MOTMS with respect to other substances, and their pore characteristics were analyzed. Then, the effects of thermal treatment on the micropore structure of the resulting silica membranes were investigated. The pore size of the silica membrane prepared after calcination at 400–700 ‡C was in the range of 0.6–0.7 nm. In addition, permeation rates through the membranes were measured in the range of 100–300 dgC using H₂, CO₂, N₂, CH₄, C₂H₆, C₃H₆ and SF₆. The membrane calcined at 600 ‡C showed a H₂ permeance of 2×10^-7-7×10^-7 molm^-2s^-1Pa^-1 at permeation temperature 300 ‡C, and the separation factors for equimolar gas mixtures were 11 and 36 for a H₂/CO₂ mixture and 54 and 132 for a H₂/CH₄ mixture at permeation temperatures of 100 ‡C and 300 ‡C, respectively.     

Surface activity of mixtures of narrow-range distributed alcohol oxyethylates and sodium dodecylbenzenesulfonate

Surface and interfacial tension, emulsion inversion temperature, and detergency were determined for mixtures of sodium dodecylbenzenesulfonate and narrow-range distributed alcohol C₁₂−C₁₄ oxyethylates of different hydrophilicity. The mixtures of ionic and nonionic surfactants behave similarly to nonionic and ionic surfactants at the air/water and hydrocarbon/water interfaces, respectively. The air/water interface is mainly occupied by nonionic surfactant molecules. However, the interfacial tensions for mixtures of nonionic and ionic surfactants are similar to those of sodium dodecylbenzenesulfonate. Mixtures of narrow-range distributed oxyethylates and sodium dodecylbenzenesulfonate have a higher detergency at 40°C than individual components.     

Chemical fixation of carbon dioxide to dimethyl carbonate from propylene carbonate and methanol using ionic liquid catalysts

The synthesis of dimethyl carbonate (DMC) through the transesterification of propylene carbonate (PC) with methanol was investigated by using imidazolium salt ionic liquid catalysts. 1-alkyl-3-methyl imidazolium salts of different alkyl group (C₂, C₄, C₆, C₈) and anions (Cl⁻, Br⁻, BF₄⁻, PF₆⁻) were used for catalysts. The reaction was carried out in an autoclave at 140–180°C under carbon dioxide pressure of 1.48–5.61 MPa. The imidazolium salts of shorter alkyl group, and more nucleophilic counter anion exhibited higher catalytic activity. The conversion of PC increased as CO₂ pressure and reaction temperature increased. Kinetic studies were also performed to better understand the reaction mechanism. This paper was presented at the 6 ^th Korea-China Workshop on Clean Energy Technology held at Busan, Korea, July 4–7, 2006.     

Natural abundance stable carbon isotope evidence for the routing and <Emphasis Type="Italic">de novo</Emphasis> synthesis of bone FA and cholesterol

This research reported in this paper investigated the relationship between diet and bone FA and cholesterol in rats raised on a variety of isotopically controlled diets comprising 20% C₃ or C₄ protein (casein) and C₃ and/or C₄ nonprotein or energy (sucrose, starch, and oil) macronutrients. Compoundspecific stable carbon isotope analysis (δ¹³C) was performed on the FA (16∶0, 18∶0, 18∶1, and 18∶2) and cholesterol isolated from the diet (n=4) and bone (n=8) of these animals. The dietary signals reflected by the bone lipids were investigated using linear regression analysis. δ¹³C values of bone cholesterol and stearic (18∶0) acid were shown to reflect whole-diet δ¹³C values. whereas the δ¹³C values of bone palmitic (16∶0), oleic (18∶1), and linoleic (18∶2) acids reflected dietary FA δ¹³C values. Dietary signal differences are a result of the balance between direct incorporation (or routing) and de novo synthesis of each of these bone lipids. Estimates of the degree of routing of these bone lipids gleaned from correlations between Δ¹³C _dlipid-wdiet (δ¹³C_{diet lipid}-δ¹³C_{whole diet}) spacings and Δ¹³C _blipid-wdiet (δ¹³C_{bone lipid}-δ¹³C_{whole diet} fractionations demonstrated that the extent of routing, where 18∶2>16∶0>18∶1>18∶0>cholesterol, reflected the relative abundances of these lipids in the diet. These findings provide the basis for more accurate insights into diet when the δ¹³C analysis of bone fatty FA or cholesterol is employed.     

The effect of hetero-aggregated feeds on critical flux

Membrane fouling by flocculated particulate mixtures formed by silica (SiO₂) and alumina (Al₂O₃) was studied. The properties of the particulate mixtures formed depended on the properties of the solutions. The effect of floc properties and temperature on the apparent critical flux was studied by flux stepping. Critical flux increased with operating temperature and decreased with pH and ionic strength of the mixture.     

Synthesis of mycolic acid biosurfactants and their physical and surface-active properties

Five mycolic acids [2-alkyl-3-hydroxy FA: R₁C^*(OH)C^*HR₂COOH] were synthesized using acyl chlorides with alkyl chains of different lengths (total carbon numbers of mycolic acids, 12, 16, 20, 24, 36). The relationship between the chemical structures of the mycolic acids and their surface-active properties was determined. The acids were synthesized in three steps: (i) dimerization of acyl chloride into alkyl ketene dimer, (ii) selective reduction of C=C to C-C by hydrogenation, and (iii) β-lactone ring cleavage under alkaline conditions. The yields of C₁₂-, C₁₆-, C₂₀-, C₂₄-, and C₃₆-mycolic acid were 72, 73, 73, 73, and 73%, respectively. The critical micelle concentrations (CMC) of C₁₂-, C₁₆-, and C₂₀-mycolic acid were 2.2×10⁻⁴, 1.36×10⁻⁴, and 7.4×10⁻⁵ M, respectively. As the carbon number increased, the surface tension at the CMC value was also lower; the values for C₁₂-, C₁₆- and C₂₀-mycolic acid were 46.54, 43.59, and 41.57 dyn/cm, respectively. The emulsifying activities of mycolic acids were determined for n-tetradecane, n-hexadecane, cyclohexane, and diesel oil. The results showed that C₁₂-mycolic acid was the best emulsifier for diesel oil, C₁₆-mycolic acid was the best emulsifier for n-tetradecane and n-hexadecane, and C₂₀-mycolic acid was the best emulsifier for cyclohexane. This study showed that mycolic acids having, surface-active properties can be chemically synthesized for potential applications in the detergent/cleaning material industries, for example, in oil spill cleanup, oil recovery, textiles, pharmaceuticals, and cosmetics.     

Crystal structures of binary systems of saturated fatty acids

Data on crystal lattices of 13 different mixtures of the system palmitic acid:stearic acid (C₁₆/C₁₈) could be obtained by means of X-ray and electron diffraction. The modification occurring in all concentrations was found to be in conformity with the known γ₄- or C-form of the pure components. It is characterized by the fact that, in mixtures with 95-60 mol % stearic acid, the shorter chained palmitic acid molecules may be incorporated in the crystal lattice of pure stearic acid without dimension c of the unit cell being changed. In concentration ranges of 50–20% C₁₈-molecules, one form of mixture which proves to be stable is characterized by constancy of nearly all unit cell parameters of various mixture ratios. From SP10 to SP0, the lattice constants of pure palmitic acid are mainly obtained. The occurrence of C₁₈-molecules of up to 10% in the unit cell of palmitic acid results in a slight decrease of the angle β by 1–2^o and an enlargement of the distance to neighbored molecules.     

Hexachloroethane as an efficient oxidizer in combustion synthesis of carbonaceous and ceramic nanostructures

Combustion of hexachloroethane (C₂Cl₆) mixtures with different reductants — such as NaN₃, B, Al, Mg, Zn, Ti, Si, CaSi₂, AlSi, TiSi, MoSi₂, CrSi₂ — was investigated. Reactions between these substrates are fast and exothermic enough to proceed in a self-sustaining regime. Heat effects accompanying the reactions were measured and the solid reaction products were analyzed. SEM observation revealed the presence of nanocrystallites and nanofibers in the products. Phase compositions of solid products were determined by XRD.     

Thermal decomposition of 3,3,6,6,9,9-hexaethyl-1,2,4,5,7,8-hexaoxacyclononane in solution and its use in methyl methacrylate polymerization

The kinetics of the thermal decomposition reaction of diethylketone triperoxide (3,3,6,6,9,9-hexaethyl-1,2,4,5,7,8-hexaoxacyclononane, DEKTP) in ethylbenzene solution were studied in the temperature range of 120.0–150.0 °C and at an initial concentration range of 0.01–0.10 M. This peroxide was used as a new initiator in methyl methacrylate (MMA) polymerization process at high temperatures (110.0–140.0 °C) in ethylbenzene solution. The effects of initiator concentration and reaction temperature on the polymerization rate were investigated in detail. Thus, activation parameters of the solution polymerization process (ΔE _d* = 83.3 kJ mol⁻¹ and ΔE _p* − ΔE _t*/2 = 54.0 kJ mol⁻¹) will be obtained. DEKTP can effectively act as initiator in MMA polymerization and its performance is similar to that presented by a multifunctional initiator resulting in high-molecular weight polymethylmethacrylate with a high reaction rate.