Hexanol Concentration Research Articles

Extraction Equilibrium of Ethanol for Bioethanol Production — Solvent Selection and Liquid-liquid Equilibrium Measurement —

Ethanol distributions between selected organic and aqueous phases were measured for recovery and concentration of bioethanol from fermented solution. The strategy of solvent selection was based on the background of biofuel production, and m-xylene was selected as the primary solvent and capric acid, 1-hexanol and 2-ethyl hexanol secondary solvents were utilized to enhance the ethanol solubility. The extraction performance was evaluated through the liquid-liquid equilibrium. m-Xylene showed low distribution coefficient of ethanol and high separation selectivity of ethanol relative to water. All secondary solvents increased the distribution coefficient. The separation selectivity was greatly reduced by capric acid, but was similar for 1-hexanol and 2-ethyl hexanol. The two phase region was smaller for 1-hexanol than for 2-ethyl hexanol, chosen as the best secondary solvent. Examination of the effects of 2-ethyl hexanol concentration in the solvent found that a small amount of 2-ethyl hexanol could enhance the distribution coefficient and maintain the separation selectivity constant. The measured liquid-liquid equilibria were estimated with the ordinary and modified UNIFAC methods. Both methods could predict the liquid-liquid equilibrium behaviors of the measured systems, but the modified UNIFAC method could show a better correlation. However, the water concentrations in the organic phases were estimated to be larger than the measured values if the measured concentrations were very low.

Mixed reverse micellar systems for extraction and purification of β-glucosidase

Mixed reverse micellar (MRM) systems of sodium bis(2-ethylhexyl)sulfosuccinate (AOT) and nonionic surfactants (Tween 20, Tween 80, Tween 85 and Triton X-100) in iso-octane were used for the extraction and primary purification of β-glucosidase (EC 3.2.1.21) from the aqueous extract of barley ( Hordeum vulgare) for the first time. Studies are carried out with both phase transfer as well as injection mode of reverse micellar extraction, among which, injection mode is observed to be more suitable for β-glucosidase extraction. The process parameters such as concentration of surfactants and their molar ratio, type of solvent, volume of sample injected and its protein concentration, pH and ionic strength of the initial aqueous phase for forward extraction, buffer pH, concentration of hexanol and salt during back extraction are varied to maximize the extraction efficiency. The molar ratio of AOT:nonionic above 4.5:1.0 only resulted in clear phase formation and below this ratio precipitation was observed at the interface during forward extraction. Mixed reverse micelles found to solubilize almost three times more volume of water and protein than AOT alone under otherwise similar conditions. Activity recovery was found to be in the order of AOT/Tween 20 > AOT/Tween 80 > AOT/Triton X-100 > AOT/Tween 85 > AOT. MRM system of 150 mM AOT/15 mM Tween 20 has resulted in maximum activity recovery of 95.18% and degree of purification of 4.8-fold.

Differentiation of monofloral citrus, rosemary, eucalyptus, lavender, thyme and heather honeys based on volatile composition and sensory descriptive analysis

The volatile profiles of 49 Spanish honey samples of different botanical origins were obtained by means of gas chromatography–mass spectrometry and sensory analysis. Citrus honeys were characterised by higher amounts of linalool derivatives, limonyl alcohol, sinensal isomers, and α-4-dimethyl-3-cyclohexene-1-acetaldehyde, together with fresh fruit and citric aromas; eucalyptus honeys had hydroxyketones (acetoin, 5-hydroxy-2,7-dimethyl-4-octanone), p-cymene derivatives, 3-caren-2-ol and spathulenol, cheese and hay aromas; lavender honeys had hexanal, nerolidol oxide, coumarin, important concentrations of hexanol and hotrienol and sensorial attributes, including balsamic and aromatic herb aromas; finally, heather honeys were characterised by high contents of benzene and phenolic compounds and ripe fruit and spicy aromas. Some of these compounds and sensory attributes were only found in honeys from a specific floral source and could thus be of interest for use as markers of their botanical origin.

Effect of Vertical Shoot-Positioned, Smart-Dyson, and Geneva Double-Curtain Training Systems on Viognier Grape and Wine Composition

Viognier grapes grown in northern Virginia and resultant wines were evaluated as a function of training system. Treatments included vertical shoot-positioned (VSP), Smart-Dyson (SD), and Geneva double curtain (GDC), with vines of all treatments spaced 2.4 m apart in 3.0 m wide rows. In addition to increased cluster numbers and crop yield, GDC training generally increased fruit zone sunlight interception and fruit exposure, while it decreased cane pruning weights per meter of cordon, compared with SD and VSP. Crop adjustments were made between bloom and veraison in six seasons, to result in average yields of 10.5 kg/vine (GDC), 9.9 kg/vine (SD), and 6.0 kg/vine (VSP), with the lower SD canopy bearing 30 to 40% less crop than the corresponding upper SD canopy. Crop loads (yield/cane pruning weight) were generally between 4 and 12; GDC crop load approached 20 in three seasons, while SD approached 14 in one. Leaf area per crop ratio was determined one season and exceeded 1.8 m²/kg of fruit for all systems. Fruit was harvested at similar Brix values, with differences in berry weight, pH, titratable acidity, and malic and tartaric acids among treatments generally not significant. Volatile compounds were analyzed using headspace solid-phase microextraction GC-MS. Fruit showed consistent differences in linalool, α-terpineol, β-damascenone, and <i>n</i>-hexanol concentrations among training systems. SD had the highest concentration of most free volatiles quantified in both juice and wines, while GDC wines frequently had the highest concentration of phenol-free glycosides. Triangle difference sensory testing demonstrated differences between GDC and SD in wine aroma and flavor and between VSP and SD in flavor. GDC wines generally had higher fruity and floral aromas compared with the other systems.

Solubilization of butanol/pentanol/hexanol in dodecylpyridinium chloride

The specific conductivities of dodecylpyridinium chloride have been determinated in water-butanol/pentanol/hexanol solutions in the temperature range of 10 to 35°C, and butanol, pentanol and hexanol concentrations up to 0.05 mol kg–1.

Structure of DNA-CTAB-hexanol complexes

We have probed structures of the complexes formed by DNA with the cationic surfactant cetyltrimethylammonium bromide in the presence of the cosurfactant hexanol, using small angle x-ray diffraction techniques. They are found to exhibit a hexagonal-->lamellar-->hexagonal transition with increasing hexanol content. Quantitative analysis of the diffraction data shows that the complexes formed at low hexanol concentrations have an intercalated hexagonal (HI) structure, whereas those formed at higher hexanol content have an inverted hexagonal (HII) structure.

An alcohol acyl transferase from apple (cv. Royal Gala), MpAAT1, produces esters involved in apple fruit flavor

Apple flavor is characterized by combinations of ester compounds, which increase markedly during fruit ripening. The final step in ester biosynthesis is catalyzed by alcohol acyl transferases (AATs) that use coenzyme A (CoA) donors together with alcohol acceptors as substrates. The gene MpAAT1, which produces a predicted protein containing features of other plant acyl transferases, was isolated from Malus pumila (cv. Royal Gala). The MpAAT1 gene is expressed in leaves, flowers and fruit of apple. The recombinant enzyme can utilize a range of alcohol substrates from short to medium straight chain (C3-C10), branched chain, aromatic and terpene alcohols. The enzyme can also utilize a range of short to medium chain CoAs. The binding of the alcohol substrate is rate limiting compared with the binding of the CoA substrate. Among different alcohol substrates there is more variation in turnover compared with K(m) values. MpAAT1 is capable of producing many esters found in Royal Gala fruit, including hexyl esters, butyl acetate and 2-methylbutyl acetate. Of these, MpAAT1 prefers to produce the hexyl esters of C3, C6 and C8 CoAs. For the acetate esters, however, MpAAT1 preference depends upon substrate concentration. At low concentrations of alcohol substrate the enzyme prefers utilizing the 2-methylbutanol over hexanol and butanol, while at high concentrations of substrate hexanol can be used at a greater rate than 2-methylbutanol and butanol. Such kinetic characteristics of AATs may therefore be another important factor in understanding how the distinct flavor profiles of different fruit are produced during ripening.

Phase diagram studies in two-surfactant ternary systems employing positron annihilation spectroscopy

Positron annihilation lifetime parameters in condensed media are sensitive to structural and conformational changes. This property has been exploited to study the phase diagrams of two ternary cationic surfactant systems. Positron lifetime measurements were performed in cetyltrimethylammonium bromide (CTAB)/water/hexanol and tetradecyltrimethylammonium bromide (TTAB)/water/pentanol systems having varying concentrations of hexanol and pentanol respectively. For both the systems, changes were observed in the positron lifetime parameters whenever a phase transformation occurred. The various phase boundaries demarcated by this technique agrees well with those obtained by other conventional techniques. Besides this, the present work suggests the existence of two kinds of lamellar structures referred to as D I and D II phases in both the systems, which were otherwise considered to be a single D phase by other conventional techniques. The existence of such lamellar structures has been demonstrated by a change in the trend of o-Ps lifetime when the system passes from one type of lamellar structure to the other type. The results of these investigations are presented.

Experimental study of the combustion dynamics of jet fuel droplets with additives in the absence of convection

Combustion of stationary JP8 fuel droplets mixed with additives is examined in a low gravity environment to reduce the influence of convection and promote spherical droplet flames. Both qualitative information on flame structure and sooting tendencies and quantitative information on evaporation rates and flame and soot shell diameters are reported. The additives were hexanol (C 6H 14O) and a commercial blend of a detergent/dispersant termed “+100” that is widely used as an additive in military transport systems. Experiments for pure nonane (C 9H 20) and hexanol droplets are also reported for comparison with single component fuels that have boiling points close to JP8. Nonane was also used for calibrating the experimental design. +100 is a commercial additive developed for JP8 to improve its thermal stability in trace quantities but its influence on combustion is essentially unknown. The hexanol concentration in JP8 was fixed to correspond to about 0.078 mass fraction of oxygenate in the JP8+hexanol mixture and the +100 concentration in JP8 was set at the commercial value (256 ppm). The initial droplet diameters for quantitative analyses were kept within a narrow range (0.40 to 0.52 mm) to eliminate consideration of the effect of initial droplet diameter in the interpretation of the results. Experiments were carried out in an oxidizing ambience containing either 79% nitrogen inert or 70% helium inert, the latter to compare results for burning under conditions where soot formation was suppressed. The lower concentration of helium inert was necessitated to allow ignition by the multiple spark arrangement used in the present investigation. Extensive droplet heating was observed for JP8 and JP8+100 in air. JP8+hexanol, along with pure nonane and hexanol, showed no evidence of droplet heating due to the lower thermal diffusion time associated with the higher thermal diffusivity of hexanol and nonane compared to JP8. The burning rate was dependent on time for burning in both air and the 70% He/30% O 2 mixture in which soot formation was virtually eliminated. Some evidence for sooting propensities in the approximate order JP8>JP8+100>JP8+hexanol was found by comparing backlighted and flame-illuminated photographs. A scaling relationship is presented that consolidates the droplet, flame, and soot shell diameters into a single curve with a power law relationship of the nondimensional burning time.

Application of factorial design to the study of an alcoholysis transformation promoted by cutinase immobilized on NaY zeolite and Accurel PA6

Fusarium solani pisi recombinant cutinase was immobilized on sodium form of zeolite Y (NaY) and polyamide Accurel PA6 and used to catalyze the alcoholysis reaction of butyl acetate with hexanol, in isooctane. The influence of some of the relevant parameters to the enzyme alcoholysis activity, such as temperature, buffer molarity and pH of the enzyme solution, hexanol and butyl acetate concentrations, were studied by means of a factorial design plan. By knowing the system response to the experimental design, the effects of each factor and its interactions were determined. In the case of the preparations with NaY zeolite, the main effects are due to temperature and buffer molarity, while pH and hexanol concentration have little effect on activity. In case of the cutinase adsorbed on Accurel PA6 the main effects are due to temperature, buffer molarity and pH of the enzyme solution.

Water activity dependence of lipase catalysis in organic media explains successful transesterification reactions

The water activity dependence of lipase kinetics in organic media was evaluated using lipases from Rhizopus oryzae and Candida rugosa immobilised on polypropene EP-100. The conversion studied was the transesterification of ethyl decanoate to hexyl decanoate with hydrolysis to decanoic acid as competing reaction. The reactions were carried out at controlled water activity in diisopropyl ether. Substrate inhibition was observed at hexanol concentrations of 100 mM or higher. The Rhizopus lipase expressed the highest activity and the best selectivity for transesterification at the lowest water activity ( a w=0.06). The Candida lipase expressed the highest transesterification/hydrolysis ratio at a w=0.11 and the highest total activity at a w=0.53. Several glycosidases previously tested under conditions similar to those used here expressed both maximal total activity and the best selectivity at water activities close to 1.0. The water activity dependence of the lipases is thus fundamentally different from that of glycosidases and it is a major part of the reason why lipases are more suited for transferase-type reactions than the glycosidases.

Biooxidation of n-hexanol by alcohol oxidase and catalase in biphasic and micellar systems without solvent.

Alcohol oxidase from Pichia pastoris together with catalase from bovine liver was used to oxidize n-hexanol to hexanal. For this purpose, an aqueous buffer solution was mixed with large amounts of hexanol by simple agitation, yielding a biphasic system, or by adding the nonionic surfactant Brij 35. Initial velocities and reaction yields after 24 h were measured as a function of various parameters such as the amounts of enzymes, hexanol, or surfactant. High enzymatic activity was determined for hexanol concentrations of between 20 mass% and 80 mass% without using any additional organic solvent. The homogenization of the biphasic systems with the help of Brij 35 did not yield a significant improvement of the bioconversion, which would justify the use of surfactants.

Screening of variables in beta-xylosidase recovery using cetyl trimethyl ammonium bromide reversed micelles.

Beta-xylosidase recovery by micelles using cetyl trimethyl ammonium bromide (CTAB) cationic surfactant was verified under different experimental conditions. A 2(5-1) fractional factorial design with center points was employed to verify the influence of the following factors on enzyme extraction: pH (x1), CTAB concentration (x2), electrical conductivity (x3), hexanol concentration (x4), and butanol concentration (x). Statistical analysis of the results shows that of the five variables studied only hexanol and electrical conductivity did not have significant effects on the recovery of beta-xylosidase. The other factors had significant effects in increasing order: (x1) > (x2) > (x5). The model predicts a recovery value of about 45%, which is similar to that obtained experimentally (43.5%).

An Integrated Model for Enzymatic Reactions in Reverse Micellar Systems: Nominal and Effective Substrate Concentrations

The distribution of hexanol in a reversed micellar system of AOT/isooctane/buffer was quantitatively described by a model based on the volume fractions of micellar components and partition coefficients of the alcohol. A recombinant cutinase was used as a model biocatalyst since its activity is strongly dictated by the presence of short to medium alcohol chain lengths. It was assumed that hexanol would be accessed by cutinase if it is either in the water pool or in the surfactant layer (micellar) since the micelles are very small and resized upon protein microencapsulation. The integrated model takes into account the partitioning, the diffusion, and the adsorption of hexanol to AOT hydrocarbon tails and the effectiveness factors calculated to model the kinetic experiments. Thermostability data also support the model generated. Therefore, the model defines the reversed micelles composition in terms of hexanol concentration integrating the process globally.

Experimental study of nonane/hexanol mixture droplet combustion without natural or forced convection

In this paper we present new data on the combustion of stationary nonane/hexanol mixture droplets burning in microgravity to promote spherical symmetry. Compositions of 10%, 25%, 40%, 60%, and 80% (volume percent hexanol) were examined in a drop tower to create an environment whereby droplets could burn without a strong influence of buoyancy. The evolution of droplet, soot shell, and flame diameter were measured, and photographs are presented to show sooting trends as composition was varied. Droplets with initial diameters between 0.46 mm and 0.57 mm were studied. The results show that dilution of nonane by hexanol reduces soot formation and decreases the droplet burning rate, the latter of which was found to be time dependent. Mechanisms for this effect which are considered include soot formation, the potential for absorption of combustion products in the droplets as they burn, and droplet heating. Because of the similarity of the boiling points of the mixture components, preferential vaporization did not occur. The droplets burned to completion, and extinction was not observed because of minimal radiative losses for the small droplet sizes examined and low propensity for water to condense on the droplet surface and dissolve in it for nonane and hexanol. A soot shell was not visible for hexanol loadings above 10%. The flame and soot shell standoff ratios increased continuously during burning. The flame diameter showed no sign of a quasi-steady behavior at any time during the combustion process. As hexanol concentration was increased, the flame moved toward the droplet.

Phase Behavior, Structure, and Physical Properties of the Quaternary System Tetradecyldimethylamine Oxide, HCl, 1-Hexanol, and Water

The phase diagram of the ternary surfactant system tetradecyldimethylamine oxide (TDMAO)/HCl/1-hexanol/water shows with increasing cosurfactant concentration an L1 phase, two Lα phases (a vesicle phase Lα1 and a stacked bilayer phase Lαh), and an L3 phase, which are separated by the corresponding two-phase regions L1/Lα and Lα/L3. In this investigation, the system was studied where some of the TDMAO was substituted by the protonated TDMAO. Under these conditions, one finds for constant surfactant concentration of 100 mM TDMAO a micellar L1 phase, an Lα1 phase (consisting of multilamellar vesicles), and an interesting isotropic L1* phase in the middle of the L1/Lα two-phase region. The L1* phase exists at intermediate degrees of charging of 30–60% and for 40–120 mM TDMAO and 70–140 mM hexanol concentration. At surfactant concentrations less than 80 mM the L1*-phase borders directly on the L1 phase. The phase transition between the L1 phase and the L1* phase was detected by electric conductivity and rheological measurements. The conductivity values show a sharp drop at the L1/L1* transition, and the zero shear viscosity of the L1* phase is much lower than in L1 phase. The form and size of the aggregates in L1* were detected with FF-TEM and SANS. This phase contains small unilamellar vesicles (SUV) of about 10 nm and some large multilamellar vesicles with diameters up to 500 nm. The system exhibits another peculiarity. For 100 mM surfactant, the clear Lα1-phase exists only at chargings below 30%. With oscillating rheological measurements a parallel development of the storage modulus G′ and the loss modulus G″ was observed. Both moduli are frequency independent and the system possesses a yield stress. The storage modulus is a magnitude larger than the loss modulus.

Cutinase stability in AOT reversed micelles: system optimization using the factorial design methodology

Fusarium solani pisi cutinase microencapsulated in reversed micelles of AOT (bis(2-ethylhexyl) sodium sulfosuccinate) was used to catalyse the alcoholysis of butyl acetate (acyl donor) with hexanol. In the present study the stability of cutinase is evaluated comparatively with the initial activity in order to obtain a set of conditions to fully optimise the system. The start conditions were selected based on a synergy of the results assigned in previous work, where relevant parameters for the cutinase activity, such as temperature, buffer molarity, pH, amount of water, surfactant, hexanol and butyl acetate concentrations were studied. Using a 2(5−1) factorial design expanded further to a central composite design (CCD), the effects of each factor mentioned above (with exception of temperature and acetate concentration) on the stability were calculated and the interactions were determined. The surface methodology applied to the results showed that cutinase, incubated at 40°C retained a high activity level (90%) after 3 days when microencapsulated at W0 (molar ratio of water to surfactant) 2.7. The W0 values in the range 5–8 led to optimal-specific activities with lower stability. A hexanol concentration of 500–600 mm was essential to prevent deactivation and at the same time allowed relatively high initial rates. A pH value of 8.0–8.55 and a buffer molarity of 200 mm were suitable for both activity and stability. Cutinase in AOT reversed micelles has been usually reported to be very sensitive to temperature, however, in this work, at an incubation temperature of 40°C, cutinase displayed half-lives significantly greater than previously stated. The main reasons for this are the presence of hexanol and the reduced water content that promote a stabilisation of cutinase structure inside the micelles. The thermostability experiments performed with the selected conditions led to a half-life of 53 days, confirming the model predictions.

Effect of hexanol as a cosolvent on partitioning and mass transfer rate of protein extraction using reversed micelles of CB-modified lecithin

Using the affinity-based reversed micelles composed of Cibacron Blue F3G-A (CB) modified soybean lecithin, the effect of hexanol as a cosolvent on the extraction of lysozyme and bovine serum albumin (BSA) was investigated. The water concentration in the reversed micelles increased significantly with increasing hexanol concentration. The partition coefficient of lysozyme could be increased by over 12-fold by introducing hexanol of higher than 0.5 vol%. However, the transfer of BSA was hardly affected because its high molecular weight resulted in a strong steric hindrance effect. The enzymatic activity of lysozyme was nearly 100% retained after undergoing the extraction process with the CB–lecithin micelles containing 3 vol% hexanol. The partitioning isotherms of lysozyme in the CB–lecithin micelles with and without hexanol addition were expressed by the Langmuir equation. The partitioning capacity of lysozyme was nearly increased twofold by introducing 3 vol% hexanol to the CB–lecithin micelles and reached 2.12 g/l. The cosolvent hexanol revealed insignificant effect on the mass transfer rate, and in both the systems with and without hexanol, the mass transfer rate in back extraction was 5–10 times slower than that in the forward extraction. This phenomenon was similar to that in conventionally employed ionic surfactant systems. The result suggests that in the present affinity-based reversed micelles, the interfacial resistance also played a more important role in back extraction than in forward extraction.

Kinetics and modelling of transesterification reactions catalysed by cutinase in AOT reversed micelles

Kinetic studies were performed with cutinase to obtain the parameters V max, K M, k CAT and K S to the alcoholysis reaction of butyl acetate with hexanol and to the reversible reaction. The values of X e and K eq were also determined. Diffusional effects were detected for hexanol concentrations lower than 350 mM and the effectiveness factors determined. The integrated rate equation for a batch stirred tank reactor was applied considering a reversible kinetics and mass transfer effects. The experimental results were successfully described by the model for intermediate concentrations of hexanol (250–450 mM).

Micelle to Vesicle Transition Induced by Cosurfactant: Rheological Study and Direct Observations

We report a micelle−vesicle transition induced by the addition of a neutral cosurfactant, hexanol, into a wormlike micellar solution of gemini cationic surfactant. This transition was investigated with rheology measurements as well as direct imaging techniques. It was observed by cryo transmission electron microscopy that micelles first become elongated with an increase of hexanol, which increases the viscosity. As the hexanol concentration is increased, another more fluid phase appears, where micelles are highly branched and coexist with small vesicles. One can describe this transition as a decrease of the spontaneous curvature caused by the cosurfactant molecule, which induces the elongation, and then the branching of micelles as well as the formation of small unilamellar vesicles. With a further increase of hexanol, these vesicles grow in size, which allows their observation by optical microscopy with differential interferential contrast. Some of these vesicles show long tubule-like shape, typically a ...