Water-organic Solvent Systems Research Articles

Rhus laccase catalysis and product characterization of 1,2-dimethoxyphenol in organic solutions

Dimethoxyphenol was a widely used substrate in determination of laccases activity. It was surprised, however, that the products of it had not been completely determined until now. Studies were thus conducted on Rhus laccase (RL) and immobilized Rhus laccase (IRL)-catalyzed oxidation of 2,6-dimethoxyphenol (DMP) in water–organic solvent systems. Only one product, 3,3′,5,5′-tetramethoxy-1,1′-biphenyl-4,4′-diol (TMBP), was produced by RL catalysis, and it was thoroughly characterized by FT-IR, NMR and GC–MS, etc.

Enhanced catalytic performance and stability of chloroperoxidase from Caldariomyces fumago in surfactant free ternary water–organic solvent systems

Surfactant free ternary systems formulated with organic solvents such as α-pinene or n-hexane, short chain alcohols and water, were used as new reaction media to maximize the catalytic performance of chloroperoxidase from Caldariomyces fumago (CPO) towards the oxidation of hydrophobic compounds including olefins and terpenols. The influence of the composition and the hydration state of the system, the nature of the oxidizing agent as well as substrate availability on the catalytic behavior and stability of the enzyme was investigated, using the chlorination of monochlorodimedone (MCD) and the epoxidation of styrene as model reactions. Based on residual chlorination activity measurements, which were in accordance with differential scanning calorimetry (DSC) findings, it was concluded that in low water systems formulated with α-pinene CPO stability is significantly increased compared to other reaction media (up to 65% residual activity after 24 h of incubation at 30 °C). Electron paramagnetic resonance (EPR) spectroscopy indicated that in low water content systems the ferric environment of the active site of CPO does not undergo severe modifications. Total turnover numbers (TTN) obtained for the oxidation of various olefins and terpenols in α-pinene-based systems, were up to 25,000 which is 2–170 times higher than previously reported values. The results indicate that such ternary systems can be efficiently employed as reaction media leading to highly enhanced stability and increase CPO potential as practical catalyst for oxidation of large amounts of hydrophobic compounds in a single-step biocatalytic process.

Renewable plant-based soybean oil methyl esters as alternatives to organic solvents

The physico-chemical properties of soybean oil methyl ester (SBME), better known as biodiesel, of importance to its use as a solvent in liquid–liquid separations have been examined. Partition coefficients of several organic species between SBME–water have been determined and compared to log P (1-octanol–water). The free energy of transfer of a methylene group has been obtained and the solvent properties of the SBME–water system determined from distribution data of a small solute set using Abraham's generalized solvation equation. Solute distribution behavior is similar to that found for conventional organic solvent–water systems, but is most similar to other vegetable oils such as olive oil. When ionizable solutes are partitioned in the SBME–water system at differing pH, the neutral species show the highest distribution. Partitioning is dependent on the solute's ability to form hydrogen bonds between water and its charged state. Metal ions (e.g., Fe3+, Co2+, and Ni2+) exhibit moderate partitioning to the SBME phase from water only in the presence of extractants. Actinides (UO22+, Am3+) exhibit significant partitioning to the SBME from aqueous solutions with the use of octyl(phenyl)-N,N-diisobutylcarbamoylmethyl phosphine oxide (CMPO). Soybean oil methyl ester may be a suitable “green” alternative for the replacement of volatile organic solvents in liquid–liquid extractions in selected applications.

Synthesis of β‐Aminophosphonates and Study of Their Acid—Base Properties and Phase Distribution in Water—Organic Solvent Systems.

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Distribution of phenoxyacetic acid in two-phase organic solvent-water systems

The distribution of phenoxyacetic acid in two-phase organic solvent-water systems and its dimerization in the organic phase were studied. Organic solvents were normal aliphatic alcohols (C5–C10), benzene, and its derivatives. The distribution (K dis) and dimerization (K dim) constants of this acid were determined. The correlations of these quantities with physicochemical parameters of the organic solvents were revealed. The influence of the organic solvent polarity, pH of the aqueous phase, and acid concentration on the physicochemical behavior of the acid in the two-phase systems was analyzed.

Synthesis of β-Aminophosphonates and Study of Their Acid-Base Properties and Phase Distribution in Water-Organic Solvent Systems

New and previously known β-aminoethylphosphonates were synthesized by addition of primary and secondary amines to vinylphosphonates, and their IR and NMR spectra were examined. Diethyl 2-diethylaminoethylphosphonate and diethyl 2-morpholinoethylphosphonate were found to be stronger bases than the corresponding aminomethylphosphonates, but all these are weaker bases than their precursors, nonphosphorylated amines. Distribution constants of β-aminophosphonates between water and some organic solvents were determined and compared with those of their α-amino homologs.

The use of Nile Red to monitor the aggregation behavior in ternary surfactant–water–organic solvent systems

AbstractTernary systems of surfactants, water and organic solvents were studied by monitoring the steady‐state fluorescence of the versatile solvatochromic probe Nile Red. We found not only that Nile Red can be used throughout the whole isotropic regions in the phase diagram, but also that subtle changes in the aggregation state of the surfactant can be monitored. The formation of inverted micelles in n‐hexane could be followed upon the addition of small amounts of water, in addition to the formation of normal micelles in water and water–organic solvent mixtures. In aqueous C12EO4 solutions the temperature‐dependent micelle‐to‐vesicle‐to‐inverted micelle transition was visualized by Nile Red fluorescence. Finally, the incorporation of solvent into the micellar interior could also be monitored using Nile Red as the probe. Copyright © 2005 John Wiley & Sons, Ltd.

Comparative Assessment of the Solvating Powers of Solvents of Different Nature with Respect to Condensed Aromatic Hydrocarbons

The solubilities of anthracene, tetracene, 1,2-benzanthracene, chrysene, pyrene, perylene, α,α'-dinaphtyl, rubrene, and decacyclene in solvents of different nature and polarity (hydrocarbons and halogenated hydrocarbons, alcohols, ketones, ethers, and esters) were determined at 20±1°C. The distribution of benzene and naphthalene in the organic solvent-water system was studied. The Gibbs energy of transfer of aromatic hydrocarbons from n-octane to organic solvents was calculated.

A membrane phase contactor for enzymatic synthesis of ZAlaPheOMe, the precursor of bitter dipeptide

Two process solutions were proposed for biochemical reactions carried out in the biphase organic solvent–water system where a membrane played the role of sustaining an interface. One of the two solutions with a passive- or active-type membrane was selected on the basis of the kinetic or diffusional regime of a particular process. Enzymatic synthesis of ZAlaPheOMe, the precursor of bitter dipeptide was discussed. On the basis of analysis of relative rates of enzymatic conversion and extraction of hydrophobic (a limiting substrate)—ZAlaOH from organic to aqueous phase, the range of the process was determined using the Hatta model. Very low values of the Hatta number were obtained which indicated that the process was carried out in the kinetic regime. Such a process solution was selected in which the enzyme was dissolved in the whole volume of the aqueous phase (passive character of the membrane). The process of ZAlaPheOMe synthesis confirmed a proper choice of the process solution; during the process the substrate concentrations in the aqueous phase were close to equilibrium concentrations. An intensive extraction of a hydrophobic product to the organic phase and high stability of the applied catalyst were observed.

Stabilization and activation of alpha-chymotrypsin in water-organic solvent systems by complex formation with oligoamines.

Formation of enzyme-oligoamine complexes was suggested as an approach to obtain biocatalysts with enhanced resistance towards inactivation in water-organic media. Complex formation results in broadening (by 20-40% v/v ethanol) of the range of cosolvent concentrations where the enzyme retains its catalytic activity (stabilization effect). At moderate cosolvent concentrations (20-40% v/v) complex formation activates the enzyme (by 3-6 times). The magnitude of activation and stabilization effects increases with the number of possible electrostatic contacts between the protein surface and the molecules of oligoamines (OA). Circular dichroism spectra in the far-UV region show that complex formation stabilizes protein conformation and prevents aggregation in water-organic solvent mixtures. Two populations of the complexes with different thermodynamic stabilities were found in alpha-chymotrypsin (CT)-OA systems depending on the CT/OA ratio. The average dissociation constants and stoichiometries of both low- and high-affinity populations of the complexes were estimated. It appears that it is the low-affinity sites on the CT surface that are responsible for the activation effect.

Isolation of myo -Inositol from Solutions by Enzymatic Biotransformation

The transferase reaction between phospholipids and inositol catalyzed by phospholipase D was studied at interfaces in water–organic solvent systems. Optimum conditions were determined for phosphatidylinositol synthesis in heterogeneous water–organic solvent systems. Hydrophobic components (phospholipids) were readily separated from water-soluble products (alcohols) in systems with organic solvents. In the hexane–water system, addition of methanol (an alcohol substrate) to the reaction medium displaced myo-inositol from the molecule of phosphatidylinositol. myo-Inositol was isolated from the mixture of its isomers using a two-step transferase reaction catalyzed by phospholipase D.

Kinetics of Base Hydrolysis of Methyl Iodide in Binary Solvents Water-Isopropyl Alcohol

The rate constants of the reaction of MeI with hydroxide ion at 298-323 K in aqueous isopropanol (isopropanol content 0-30 mol %) were measured. The effects of solvation of the reactants and activated complex were separated. The contributions of particular types of interactions to the solvation of the charged species were calculated. The results were compared with data for three other water-organic solvent systems.

Catalytic membrane preparation for enzymatic hydrolysis reactions carried out in the membrane phase contactor

Two concepts of the localisation of hydrolytic enzymes with the use of a membrane phase contactor are presented in the paper. Because of the participation of water molecules in the process, the enzyme should be immobilized so that it could be in contact with the aqueous phase. Thus, enzyme immobilisation on the hydrophobic membrane surface and in the hydrophilic membrane pores was considered. The lipase from Candida antarctica and from pancreatic porcine were selected for experiments. Both enzymes were adsorbed on the polypropylene membrane surface, packed in the pores of nitrocellulose and cellulose membranes and bound within the pores of the polyamide membrane after its activation with glutaraldehyde. On the basis of the amount of immobilized protein, enzyme activity and stability, the most appropriate preparation of each immobilized lipase was chosen having on mind its further application in the biphase organic solvent—water system.

A Kinetic Examination of Penicillin Acylase Stability in Water-organic Solvent Systems at Different Temperatures

We have studied the thermal stability of penicillin acylase from Streptomyces lavendulae in water-organic solvent monophasic systems at the range of temperatures between 40 and 60°C. We found a linear correlation between the log u P value of the solvent and the activation free energy for denaturation ( j G d ) at all temperatures tested. Thermodynamic analysis of the results indicates that solvents with log u P h m 2.3 have protective effects, whereas solvents with log u P S m 1.8 are deleterious for penicillin acylase.

Studies of Erythromycin Maltobionate, a New Derivative of Erythromycin

Erythromycin maltobionate, a new water-soluble derivative of erythromycin, was prepared, and its physicochemical and biological properties were evaluated. The derivative has considerable solubility in organic solvents. Its partition coefficient data in different organic solvent-water systems indicate it is possibly well distributed in various tissues in vivo. Antimicrobial potency in vitro of the derivative is 589 μg/mg, and its antimicrobial spectrum is comparable to that of the parent antibiotic. The LD50 value of the new derivative in mice intraperitoneally is 244.7 mg/kg. Results of this and the previous investigation of pharmacokinetics and protein binding indicate that the new derivative erythromycin maltobionate has a potential for possible clinical application.

Preparation and Evaluation of Erythromycin Fumarate-A New Derivative of Erythromycin

Erythromycin fumarate, a new water-soluble derivative of erythromycin, was prepared and its physicochemical and biological properties were evaluated. The derivative also has considerable solubility in organic solvents. Its partition coefficient data in different organic solvent-water systems may indicate that it is well-distributed in various tissues in vivo. Antimicrobial potency in vitro of the derivative, 725 μg/mg, is much higher than that of the existing derivatives and its antimicrobial spectrum is comparable to that of the parent antibiotic. The LD50 value of the new derivative in mice intraperitoneally is 402.7 mg/kg. Results of this and the previous investigation on pharmacokinetics and protein binding indicate that erythromycin fumarate has high potential for possible clinical application and further investigation may be undertaken.

Stability of hydrolytic enzymes in water-organic solvent systems

The effects of organic solvents on the stabilities of bovine pancreas trypsin, chymotrypsin, carboxypeptidase A and porcine pancreas lipase were studied. Water-miscible solvents (ethanol, acetonitrile, 1,4-dioxane and dimethyl sulfoxide) and water-immiscible solvents (ethyl acetate and toluene) were used in 100 mM phosphate buffer (pH 7.0) or 100 mM Tris/HCl buffer (pH 7.0) in concentrations of 20–80% (v/v). All hydrolytic enzymes studied were inactivated by mixtures containing dimethyl sulfoxide at higher concentrations. Trypsin and carboxypeptidase A resisted solvent mixtures containing acetonitrile, 1,4-dioxane and ethanol. They preserved more than 80% of their starting activities during 20-min incubations. The activities of lipase and chymotrypsin decreased with increasing concentration of water-miscible polar organic solvents, but at higher concentrations (80%) 70–90% of the activity remained. In mixtures with water-immiscible solvents, the decrease in activity of carboxypeptidase A was pronounced. Trypsin and chymotrypsin underwent practically no loss in activity in the presence of toluene or ethyl acetate. In respect of stability, the polar solvent proved to be more favorable for lipase. These results suggest that the conformational stabilities of hydrolytic enzymes are highly dependent on the solvent-protein interactions and the enzyme structure.

ChemInform Abstract: Hydroformylation of Terminal Olefins in Water‐Organic Solvent Systems in the Presence of a Rhodium Complex Based on Functionalized Polyethyleneoxide.

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A novel synthesis method for cyclodextrins from maltose in water-organic solvent systems.

A novel enzymatic synthesis method of cyclodextrin (CD) from low-mol-wt maltose using cyclomaltodextrin glucanotransferase (CGTase) from Bacillus macerans has been developed in various water-organic solvent systems. A beta-CD was synthesized in a two-phase system consisting of water and cyclohexane. However, no CDs could be synthesized in an aqueous buffer solution. A maximal yield of beta-CD has been obtained at a cyclohexane content volume of 44%. This synthesis has been obtained only at low temperatures, i.e., 7 degrees C, and did not take place at 50 degrees C. In addition, various organic solvents have been used for the enzymatic synthesis of CD from maltose. Consequently, beta-CD could be synthesized in various water-organic solvent systems, e.g., cyclohexane, benzene, xylene, and chloroform, but no enzymatic reaction occurred using aliphatic n-hydrocarbon solvents such as hexane, dodecane, and hexadecane. Furthermore, alpha- and beta-CD could be synthesized in water mixture solutions using organic solvents having an alcoholic group (e.g., ethanol, propanol, butanol, and pentanol) in a wide range of the reaction temperatures, typically 7-50 degrees C. In this temperature range, alpha- and beta-CD were also formed and the maximal yield from maltose to beta-CD of approx 13% was reached in 60 h.

Phase-transfer catalysis in reactions of electrophilic aromatic substitution

Electrophilic substitution in aromatic compounds under conditions of phase-transfer catalysis is considered. Catalysts of phase transfer of electrophilic reagents are used; their efficiency and the mechanism of their action in organic solvent-water systems are discussed.