Increasing Methanol Concentration Research Articles

Pretreatment of immobilized Candida antarctica lipase for biodiesel fuel production from plant oil

The effects of the pretreatment of immobilized Candida antarctica lipase enzyme (Novozym 435) on methanolysis for biodiesel fuel production were investigated. Methanolysis progressed much faster when Novozym 435 was preincubated in methyl oleate for 0.5 h and subsequently in soybean oil for 12 h. The initial reaction rate of methanolysis catalyzed by both the non-treated and preincubated enzyme decreased significantly with increasing water content. The initial reaction rate increased with increasing methanol content, showed a maximum, and thereafter decreased when the methanol content was increased further. The variation of the initial reaction rate with the methanol content was therefore analyzed using a Michaelis-Menten-type equation with substrate inhibition. Based on this equation, a procedure for the stepwise addition of methanol to the reaction mixture so as to maintain the desired methanol content was determined. When preincubated Novozym 435 was used, the ME content reached over 97% within 3.5 h by stepwise addition of 0.33 molar equivalent of methanol at 0.25–0.4 h intervals.

Semicontinuous methanol biosynthesis by Methylosinus trichosporium OB3b

Methylosinus trichosporium OB3b is a methanotrophic bacterium containing methane monooxygenase, catalyzing hydroxylation of methane to methanol. When methane is oxidized, the product is subsequently oxidized by methanol dehydrogenase contained in the same bacterium. To prevent further oxidation of methanol, the cell suspension was treated by cyclopropanol, an irreversible inhibitor for methanol dehydrogenase, leading to extracellular methanol accumulation. However, the batch type of methanol synthesis by M. trichosporium OB3b was terminated at ca. 6 mM of methanol, for MMO is inhibited by increasing methanol concentration. For prolonged methanol accumulation, a semicontinuous process was carried out. In this process, the reaction was repeated several times and the produced methanol was 36.1 μmol for 6 h.

Selectivity of Some Ion Chromatography Stationary Phases for Small Anions in Solvent–Water Mixtures with Hydroxide

The selectivity of two hydroxide-selective ion chromatography stationary phases was examined with varying solvent composition. The solvents acetonitrile 2-propanol and dimethylsulfoxide were found to diminish retention of these anions. However, retention times were found to increase for small anions with increasing methanol composition. For somewhat larger anions such as perchlorate and tetrafluoroborate, moderately decreasing or stable retention times were observed with increasing methanol content. The loss of retention is attributed to hydroxide form resins preferentially imbibing water from the solution phase, effectively increasing the elution strength of hydroxide because of its greater hydration energy. In methanol–water mixtures to 40%, these types of anion exchangers are known to swell to nearly the same extent (volume) as in water. Thus, hydration energy differences between hydroxide and these anions may not be as pronounced relative to weaker solvation in methanol. Run time for common inorganic anions on a high-capacity anion-exchange column can be reduced from 30 to 10 min through the use of acetonitrile. In addition, as the acetonitrile content is increased, retention reversals such as bromide–nitrate and chloride–nitrite occur. Four divalent species (sulfite, maleate, sulfate, fumarate) that are not separated on Dionex IonPac AS11 with hydroxide can be separated on the same column easily in 50% methanol.

Investigation of the OH stretching vibration of CD 3OH in CCl 4

The OH stretching vibration of CD 3OH in CCl 4 has been investigated by FTIR spectroscopy in the concentration range 0.1 – 100 mol%. At low methanol concentrations the spectra are dominated by a relatively sharp band centred at 3644 cm −1, originating from OH oscillators not donating a hydrogen bond. The proportion of these decreases rapidly with increasing methanol concentration, and are not observable in pure methanol with the present experimental precision. Instead, a broad band envelope appears at lower wave numbers (3316 cm −1in pure CD 3OH). This band contains contributions from the various hydrogen-bonded aggregates present and is not possible to decompose into components unless additional assumptions are made. Finally, a band centred at 2790 cm −1 is present. This band has not been previously reported in the literature, probably because for CH 3OH it is obscured by the CH stretching vibrations. This band is tentatively assigned to cyclic tetramers as indicated by quantum chemical calculations.

Molar Conductance of the Complexes of 18-Crown-6 with Alkaline Earth Metal Ions in Methanol + Water

The molar conductance of complexes of Mg2+, Ca2+, Sr2+, and Ba2+ with 18-crown-6 in 0−90 mass % methanol−water has been measured at temperatures from 278 K to 313 K. The observed molar conductances Λ were found to decrease for mole ratios less than unity. The conductance data have been analyzed using a model involving 1:1 complexation stoichiometry to give the stability constant K and limiting molar conductance Λc for each 1:1 complex by using a nonlinear least-squares analysis. The log K values for the resulting 1:1 complexes increased with an increase in methanol concentration and with a decrease in temperature. The stability constants determined for each metal−ligand system at each solvent composition were fitted by the equation log K = a/T + b + cT. Values of ΔG°, ΔH°, ΔS°, and ΔCp° have been calculated. The results are discussed in terms of their dependence on temperature and solvent composition. In 0−90 mass % methanol, the complexation process follows the order Ba2+ > Sr2+ > Ca2+ > Mg2+.

Lipophilicity determination of some potential photosystem II inhibitors on reversed-phase high-performance thin-layer chromatography.

The retention characteristics of 25 2-cyano-3-methylthio-3-substituted amine-acrylates are determined using reversed-phase thin-layer chromatography (RP-TLC) with methanol-water mixtures as eluents. The relationship between Rm values and partition coefficients (C log P) are established. The Rm values decrease linearly with increasing methanol concentration in the eluent. The Rm values extrapolated to zero organic modifier concentration (Rm0) in the eluent are highly related to C log P. The Rm0 value can be used to evaluate the lipophilicity of this kind of compound.

Effects of Mobile-Phase Composition and Temperature on the Selectivity of Poly(N-isopropylacrylamide)-Bonded Silica Gel in Reversed-Phase Liquid Chromatography

We developed a simple preparation method for poly(N-isopropylacrylamide) (poly(NIPAM))-bonded silica using a water-organic two-phase system to directly copolymerize N-isopropylacrylamide with 3-(methacryloxy)propyl moieties on the silica surfaces. The stationary phase showed a phase transition with the change in temperature or in methanol content, resulting in notable changes in selectivity which cannot be expected with alkyl-type stationary phases. The packing material showed an increase in retention and column efficiency with the increase in temperature between 30 and 40 °C or in methanol content between 10 and 20%. The temperature-responsive properties were reduced with the increase in methanol content of the mobile phase and lost at 40% or higher. Significant changes in retention selectivity by the addition of methanol were observed for benzene derivatives below the transition temperature of poly(NIPAM). The preferential retention of hydrogen bond acceptors was observed at low temperatures in the mobile phase of low methanol content, while dominant contribution of the hydrophobic interaction to the retention of solutes was observed at the higher temperature in aqueous mobile phase or at the higher methanol concentration. The temperature increase brought about similar changes in retention behavior of the poly(NIPAM)-bonded silica packing materials to the addition of methanol to the mobile phase.

Ionic behavior across charged membranes in methanol–water solutions. I: Membrane potential

The membrane potential across cation- and anion-exchange membranes was measured for LiCl methanol–water solutions. The experimental data were analyzed on the basis of the Donnan equilibrium and the Nernst–Planck equation of ion flux, considering the effect of mean activity coefficient of electrolytes in the external solution, and the theoretical predictions agreed well with the experimental data. The effective membrane charge densities and the cation-to-anion mobility ratios in membranes were determined by a non-linear regression method. The results showed that the effective membrane charge density would decrease with the increase in the weight fraction of methanol. It is postulated that the counter-ions prefer to make ion pairs with the fixed charge groups in the mixed solvent system since the dielectric constant of methanol is smaller than water. Thus the ion pairs between the counter-ions and fixed charge groups will increase with the increase in methanol concentration, and the effective membrane charge density will decrease.

Coelectroosmotic separations of anions in non-aqueous capillary electrophoresis

The suitability of hexadimethrine bromide (HDB) as electroosmotic flow (EOF) modifier in non-aqueous capillary electrophoresis was investigated. Using HDB as EOF modifier a reversed EOF resulted, which allows very fast separations of anionic compounds in the coelectroosmotic mode. This is demonstrated for the separation of hydroxy- and dihydroxybenzoic acids in various acetonitrile–methanol mixtures. According to the decreasing ratio of dielectric constant and viscosity the EOF mobility showed a linear decrease with increasing methanol concentration in the electrophoresis medium, whereas the analytes showed non-uniform behaviour on addition of methanol. The EOF reproducibility of EOF migration time was excellent, if the concentration of HDB in the running electrolyte was 0.001% (w/v). With this concentration a reproducibility of <0.5% R.S.D. was achieved for nine consecutive runs.

Investigation of Interactions Between Drug Enantiomers and Flavoprotein as a Chiral Selector by Affinity Capillary Electrophoresis

Interactions between drug enantiomers and flavoprotein as a pseudo chiral stationary phase were investigated by using affinity capillary electrophoresis (CE) in order to avoid the effects of nonspecific interactions that occur in chiral HPLC. Circular dichroism (CD) measurement was used to monitor changes of the secondary structure of flavoprotein under various analysis conditions in affinity CE. The chiral discrimination region for ketoprofen on the flavoprotein surface was concluded to consist of α-helix structure, and the decrease of chiral separation ability with increase of methanol content in the electrophoretic buffer was directly related to conformational change of the α-helix. Studies with chemically modified flavoprotein indicated that two types of interaction at the chiral discrimination region are required for chiral separation: π-π interaction of a tryptophan residue with the aromatic ring of ketoprofen, and ionic interaction of the carboxyl group of ketoprofen with an amino group and a carboxyl group of the protein.

Effect of Methanol Concentration on CTAB Micellization and on the Formation of Surfactant-Templated Silica (STS)

We use light-scattering techniques to study the effects of methanol concentration on alkaline, cetyltrimethylammonium bromide (CTAB) water:methanol micellar solutions. We use X-ray diffraction, SEM, TEM, 29Si NMR, and gas sorption measurements to study the structure, microstructure, and porosity of surfactant-templated silica (STS), synthesized by adding tetramethoxysilane (TMOS) to the above micellar solutions. The measured critical micelle concentration (cmc) for CTAB at 25 °C in a 0.22 M NaOH (pH 13.2) solvent increases from ∼1.3 × 10-3 M for r = 0% to ∼5.5 × 10-2 M for r = 60% (where r is the wt % methanol in the mixture) as the concentration of methanol increases. In turn, the long-range order of STS decreases as the methanol concentration increases. Ordered STS forms for 0 ≤ r 90% transparent, amorphous chemical gels fo...

Pectin Methylesterase Regulates Methanol and Ethanol Accumulation in Ripening Tomato (Lycopersicon esculentum) Fruit

We provide genetic evidence that the production of methanol in tomato fruit is regulated by pectin methylesterase (PME, EC 3.1.1.11), an enzyme that catalyzes demethoxylation of pectins. The role of PME in methanol production in tomato fruit was examined by relating the tissue methanol content to the PME enzymatic activity in wild-type Rutgers and isogenic PME antisense fruits with lowered PME activity. In the wild-type, fruit development and ripening were accompanied by an increase in the abundance of PME protein and activity and a corresponding ripening-related increase in methanol content. In the PME antisense pericarp, the level of methanol was greatly reduced in unripe fruit, and diminished methanol content persisted throughout the ripening process. The close correlation between PME activity and levels of methanol in fruit tissues from wild-type and a PME antisense mutant indicates that PME is the primary biosynthetic pathway for methanol production in tomato fruit. Interestingly, ethanol levels that were low and unchanged during ripening of wild-type tomatoes increased progressively with the ripening of PME antisense fruit. In vitro studies indicate that methanol is a competitive inhibitor of the tomato alcohol dehydrogenase (ADH, EC 1.1.1.1) activity suggesting that ADH-catalyzed production of ethanol may be arrested by methanol accumulation in the wild-type but not in the PME mutant where methanol levels remain low.

MD simulation of a NaCl solution in equimolar methanol–water mixture

Molecular dynamics simulations of the equimolar methanol–water mixture and NaCl solution in this binary solvent at room temperature have been performed. The solvent molecules have been described using three-site flexible models. The structural properties of the binary solvent and NaCl solution confirm the tendencies previously observed. Both ions are preferentially solvated by the methanol molecules, but this phenomenon vanishes gradually with increasing methanol concentration.

Some properties and the inclusion behavior of three positional isomers of 6(1),6n-di-O-alpha-D-glucosyl-cyclomaltoheptaoses (beta-cyclodextrins).

Three positional isomers of 6(1),6n-di-O-alpha-D-glucosyl-cyclomaltoheptaose [1,n-(G)2-beta CDs; n = 2-4] which existed in the digests with glucoamylase of the products from cyclomaltoheptaose (beta-cyclodextrin, beta CD) and maltose with Klebsiella pneumoniae pullulanase, were purified by HPLC. The solubilities of two isomers of those doubly branched beta CDs, 1,2- and 1,3-(G)2-beta CDs, in water were much higher than those of parent non-branched beta CD and mono-branched beta CD, 6-O-alpha-D-glucosyl-beta CD (G-beta CD), while the solubility of another isomer, 1,4-(G)2-beta CD, was significantly lower than these two isomers, though it was higher than that of beta CD. On the other hand, the solubilities of 1,2- and 1,3-isomers in 10, 30, and 50% (v/v) aqueous methanol at 25 degrees C were independent of methanol concentrations and their solubilities were the same as those in water at 25 degrees C. However, that of 1,4-isomer increased with increasing methanol concentrations. The hemolytic activities of 1,n-(G)2-beta CDs on human erythrocytes in isotonic solution were lower than those of G-beta CD and beta CD, and became weaker in the order of 1,4- > 1,2- > 1,3-isomers. The complex-forming abilities of 1,n-(G)2-beta CDs for digitoxin, digoxin, fluorometholone, flurbiprofen, hydrocortisone acetate, and norfloxacin were about the same as those of beta CD and G-beta CD, whereas reserpine was more difficult to include within 1,n-(G)2-beta CDs than beta CD and G-beta CD. Nevertheless, the solubilities of those guest compounds were much more enhanced by 1,n-(G)2-beta CDs and G-beta CD than by beta CD.

Curvilinear increase in methanol concentration after inhibition of oxidation by ethanol: significance for the investigation of endogenous methanol concentration and formation.

Endogenous methanol production was assessed over a period of 5 h in subjects given an infusion of ethanol to inhibit methanol oxidation in the liver after a period of fasting and abstinence from alcohol. Ethanol was administered to each of five subjects at rates of 0.35 g/kg per hour and 0.70 g/kg per hour. The rise in methanol concentration was biphasic regardless of the rate of ethanol administration, with a steeper gradient in the first 10-30 min. This may be due to the existence of a deep compartment from which methanol can be displaced by ethanol. This could take the form of loose binding of methanol to the hepatic oxidation enzymes as an enzyme-substrate complex, or a shift of the oxidation-reduction equilibrium between methanol and formaldehyde. The biphasic nature of the increase, with an initial steeper rise, means that the values obtained in the first 30 min should be excluded from the calculations when the rate of endogenous methanol production is determined by linear regression analysis. Endogenous methanol concentrations to be taken into account after ethanol administration are on average 0.4-0.6 mg/kg higher than those detectable in the absence of ethanol due to the additional method displaced from the deep compartment.

Spectral Characteristics and Colloidal Properties of Chlorophyll a‘ in Aqueous Methanol

The “phase behavior” of chlorophyll a‘ (Chl a‘, C132-epimer of Chl a) dissolved in aqueous methanol was examined in terms of the composition of the solvent. This study aimed at elucidating the property of Chl a‘, the exotic pigment found in a photosynthetic reaction center complex, as well as at clarifying the nature of the Chl aggregation in aqueous media. Visible absorption, circular dichroism (CD), fluorescence and resonance Raman spectroscopies, dynamic light-scattering measurements, and electron microscopy were utilized. Chl a‘ formed either of two types of colloids depending on the solvent composition. The one formed over a wide methanol volume percentage (ca. 73−30%) commonly possessed a single microscopic structural unit that yielded the double-peaked absorption (ca. 690 and 715 nm) accompanied by a symmetric dispersed-type CD spectrum. Increasing methanol concentration within this solvent composition range enhanced the size of the colloid and finally caused critical opalescence, which was reminiscent of the critical behavior of the aqueous solution of nonionic surfactants. These findings indicate that the microscopic structure of the Chl a‘ aggregate was independent of the size and shape of the colloid. This is in sharp contrast to the solvent composition dependence of the Chl a aggregation in the same medium: an increase in methanol concentration in going from 40% to 70% (vol/vol) shifted a broad red-most absorption band from ca. 700 to 750 nm, which was correlated to the enhancement of the aggregation number and the colloidal size. The difference between the aggregation behaviors of Chl a and a‘ suggests a narrower choice of possible molecular arrangements in the Chl a‘ aggregate as an inherent property of the pigment. The nature of the Chl aggregation in aqueous media is discussed in relation to the micellization of nonionic surfactant.

Quantitative approach for the prediction of preferential sorption in the case of pervaporation of a physico-chemically similar binary mixture

Selective transport by pervaporation of physico-chemically similar and polar components through a polar membrane is complicated due to competitive sorption and diffusion phenomena. In the present study the mechanism of preferential sorption has been predicted for such a system, methanol-ethylene glycol-cellophane. The mechanism has been explained in terms of intercrystalline swelling of the polymer matrix in presence of increasing methanol concentration in the feed. The reduction in preferential sorption at increasing wt% of methanol in the feed may be due to the increasing accessibility of the membrane towards ethylene glycol. This phenomenon has been quantitatively explained by considering a non-linear dependence on concentration of the binary liquid-polymer interaction parameter. Theoretical sorption data have been derived from the Flory-Huggins thermodynamics by using the swelling equilibrium condition. The coupling and plasticization phenomena in sorption are explained in terms of liquid-polymer interaction parameters. The theoretical results show good agreement with previously published experimental data.

Methanogenic fermentation and growth of granular methanogenic sludge on a methanol-propionate mixture

The effect of methanol on the methanogenic fermentation of propionate and the growth of granular methanogenic sludge on a methanol-propionate mixture was studied. Degradation of propionate was markedly inhibited by the addition of methanol (0.5 to 8.6 g/ l) to the synthetic propionate basal wastewater. When the methanol was completely consumed by methanol-degrading bacteria, propionate degradation was restored. Upflow anaerobic sludge blanket (UASB) reactors were operated at a volumetric loading rate of 7.3 g propionate/ l·d with and without addition of methanol at a space velocity of 2.2 d −1. In a run of propionate basal wastewater, a propionate removal efficiency of more than 96% could be maintained, while efficiency decreased gradually to 25% with increasing methanol concentrations up to 8.6 g/ l, giving methanol removal efficiencies of more than 85%. In all runs, granular growth of methanogenic sludge occurred successfully, and larger-sized granules were obtained on methanol-propionate mixtures rather than on propionate basal wastewater. Microscopic observation and identification of corrinoid showed that Methanosarcina spp. was the predominant species of methanol-degrading bacteria, indicating that methanol was directly converted to methane. The results indicated that spontaneous growth of granules occurred on methanol-propionate mixtures and that methanol inhibition was due to the toxicity of methanol to propionate-degrading bacteria.

Ester synthesis in aqueous media in the presence of various lipases

The ability of seven lipase preparations to catalyse methyl ester synthesis in aqueous media was compared and the synthesis reaction (esterification or alcoholysis) determined. Three behaviours were observed: three enzymes catalysed ester synthesis by esterification of free fatty acids and one enzyme catalysed alcoholysis but the other three lipases did not catalyse a net ester synthesis under the conditions tested. The three groups also differed by the influence of methanol on the hydrolysis reaction. The first group was not significantly inhibited up to the highest methanol concentration tested (5 M). Hydrolysis in the presence of the enzyme of the second group was increasingly inhibited with increasing methanol concentrations. In the presence of the third group, hydrolysis was 40 to 50% inhibited for all the concentrations tested (0.2–5 M).

Establishment of a reliable extraction method of estrone sulfate from bovine plasma for detection of the peripheral level during the regular estrous cycle by radioimmunoassay

A simple extraction and assay technique of estrone sulfate in bovine blood was developed with the object of detecting the peripheral level of estrone sulfate in a normal estrous cycle or in early pregnancy. Estrone sulfate in bovine plasma was extracted with a small reversed phase cartridge. The steroid conjugate retained in the cartridge was eluted with 40% (v/v) methanol. Estrone sulfate was separately recovered from other steroids by the stepwise increase in methanol concentration in the elution solvent. The recoveries of estrone sulfate eluted with 40% methanol were more than 90%, irrespective of the applied plasma volume. The concentration measured by radioimmunoassay with the eluent of 40% methanol was consistent for plasma extraction volumes of 0.5–2.0 ml. The change of estrone sulfate in bovine peripheral plasma during the regular estrous cycle was determined with a small reversed phase cartridge for extraction and 40% methanol for elution. The change in estrone sulfate was found to be similar to the change of estrone and estradiol-17β. The concentration of estrone sulfate was not higher than that of both estrogens in cattle.