Salt Aqueous Two-phase Systems Research Articles

Insights on the downstream purification of fucoxanthin, a microalgal carotenoid, from an aqueous two-phase system stream exploiting ultrafiltration

Alcohol–salt aqueous two-phase systems (ATPS) have shown promising results in the primary recovery of fucoxanthin from microalgae. However, the need of further operations to continue with the purification of the compound is required. In this sense, the use of ultrafiltration to process an ethanolic ATPS stream where fucoxanthin is recovered is explored in this work. Addition of ethanol to the original recovered ATPS ethanolic stream to a final relation of 74.15 % (w/w) resulted in the reduction of fucoxanthin unspecific losses in the membrane while incrementing its recovery. In fact, the ultrafiltration processing of the diluted ATPS sample presented a reduction of approximately 16 % of the proteic impurities, increasing product purity with a recovery of about 63 % of the compound in the permeate. These results show the potential of ultrafiltration in recovering molecules from ATPS streams in an easy-to-implement and economical manner avoiding a major setback in the industrial implementation of this unitary operation.

Primary recovery of a bacteriocin-like inhibitory substance derived from Pediococcus acidilactici Kp10 by an aqueous two-phase system

A polymer–salt aqueous two-phase system (ATPS) consisting of polyethylene–glycol (PEG) with sodium citrate was developed for direct recovery of a bacteriocin-like inhibitory substance (BLIS) from a culture of Pediococcus acidilactici Kp10. The influences of phase composition, tie-line length (TLL), volume ratio (VR), crude sample loading, pH and sodium chloride (NaCl) on the partition behaviour of BLIS was investigated. Under optimum conditions of ATPS, the purification of BLIS was achieved at 26.5% PEG (8000)/11% sodium citrate with a TLL of 46.38% (w/w), VR of 1.8, and 1.8% crude load at pH 7 without the presence of NaCl. BLIS from P. acidilactici Kp10 was successfully purified by the ATPS up to 8.43-fold with a yield of 81.18%. Given that the operation of ATPS is simple, environmentally friendly and cost-effective, as it requires only salts and PEG, it may have potential for industrial applications in the recovery of BLIS from fermentation broth.

A hybrid GMDH neural network to investigate partition coefficients of Penicillin G Acylase in polymer–salt aqueous two-phase systems

To model partition coefficients of Penicillin G Acylase in polymer–salt aqueous two-phase systems (ATPS), a hybrid GMDH neural network is presented on the basis of original GMDH approach. We performed two major amendments to the structure of original approach in order to enhance the model complexity and power to trace high order of non-linearity. An extensive data set observed by Pazuki et al. is examined by original GMDH approach and hybrid GMDH neural network model. Compared to results generated by original GMDH approach and UNIFAC-FV model, hybrid model stands out with a noticeable superiority in tracking data trend. Average Absolute Deviation percent (AAD%) of proposed hybrid model is 4.04% which indicates a superior accuracy in comparison with those of original GMDH approach and UNIFAC-FV model with AADs% of 6.91% and 5.58%.

Measurements and Modeling of Liquid–Liquid Equilibrium of Polyethylene Glycol 400, Sodium Phosphate, or Sodium Citrate Aqueous Two-Phase Systems at (298.2, 308.2, and 318.2) K

Experimental equilibrium data were obtained for aqueous two-phase systems composed of polyethylene glycol 400 g·mol–1 + sodium phosphate, and polyethylene glycol 400 g·mol–1 + sodium citrate, at T = (298.2, 308.2 and 318.2) K. For the system formed by sodium phosphate, at the studied range, the temperature effect on the position of the binodal curves was not relevant. For the system composed of sodium citrate, the temperature increase caused an expansion of the biphasic region. The efficacy of the salts in inducing phase segregation follows the order sodium phosphate > sodium citrate at temperatures of (298.2 and 308.2) K. Energy interaction parameters for the NRTL and UNIQUAC models were estimated, and the mean deviations between experimental and calculated compositions were 0.46 % and 0.32 %, respectively. These results show that both models, NRTL and UNIQUAC, are able to represent the phase behavior of polymer–salt aqueous two-phase systems evaluated.

Purification of a novel protease enzyme from kesinai plant (Streblus asper) leaves using a surfactant–salt aqueous micellar two-phase system: a potential low cost source of enzyme and purification method

Serine protease from kesinai leaves was purified for the first time by a surfactant–polymer aqueous micellar two-phase system. The effectiveness of different types and concentrations of non-ionic surfactants (Pluronic series and X-114) on the partitioning behaviour of the protease was evaluated. The results showed that the enzyme preferentially partitioned into the bottom surfactant-rich phase, while the hydrophilic amino acid preferred the top aqueous phase. This distribution of the enzyme is due to the hydrophobic interaction of the serine protease with the hydrophobic lid of the micelle core in the bottom phase. The influence of different types of salts (K2SO4, KH2PO4, KCl and KNO3) on the purification and selectivity of the enzyme was determined. The protease partitioning in the bottom phase increased in the presence of KNO3, which confirmed that the salt was able to improve the protein solubility in bottom phase and increase the hydrophobic interaction between the two phases. In addition, the protease from the bottom phase was re-extracted to a new aqueous phase solution to remove and recycle the surfactant. Addition of potassium thiocyanate led to the partitioning of the enzyme in top aqueous phase due to high ionic strength of SCN−, which forced the lighter micellar phase toward the upper position of the system. A high purification factor (10.3) and yield of 92 % of the enzyme were achieved in a solution of 31 % of Pluronic L61 using 0.3 % KNO3 and 50 % crude feedstock at pH 7.0.

Measurement of cephalexin partition coefficients in PEG + K2HPO4 + H2O aqueous two-phase systems at 301.15, 306.15 and 311.15 K

In this study, the liquid–liquid equilibrium (LLE) data for poly(ethylene glycol) with molecular weights 1500 and 6000 — K2HPO4 aqueous two-phase systems containing cephalexin antibiotic have been measured at three temperatures 301.15, 306.15 and 311.15K. The effects of temperature, PEG molecular weight and concentrations of PEG and salt have been studied on the LLE data. Also, the partitioning of cephalexin in PEG–salt aqueous two-phase systems has been estimated using the LLE data. The experimental data showed that the concentration of salt has a large effect on the partitioning of cephalexin in aqueous two-phase systems.

Effect of Aqueous Two-Phase System Constituents in Different Poly(ethylene glycol)–Salt Phase Diagrams

Eight different poly(ethylene glycol) (PEG)/salt aqueous two-phase systems (ATPS's) were characterized at 23 °C. PEGs with different molecular weights (1500 and 8000) were combined with different salts (sodium or potassium citrates and formates) to study the effect of each ATPS constituent in the phase diagram. The binodal curve and several tie-lines were determined for each system using common analytical techniques described in the literature for ATPS's (cloud point method, conductivity, and gravimetric analysis after lyophilization). According to the results, it was found that each ATPS constituent produced a particular effect in the phase diagram. For the salts, changes in the anion produced larger variations in the heterogeneous region size than changes of the cation. Thus, the effect of salt type seems to be largely dependent on the anion, which makes the dominant contribution. The ability to form ATPS's is connected with the Gibbs energy of hydration, ΔGhyd, of the anions: more negative ΔGhyd values facilitate ATPS formation. Changes in the PEG molecular weight affected also the phase diagram: the size of the heterogeneous region increases with the increase in the polymer molecular weight.

The Research for the Extraction of Yeast’S Nucleic Acid with [BMIM] BF<sub>4</sub>-H<sub>2</sub>O-KH<sub>2</sub>PO<sub>4</sub> Ionic Liquid Aqueous Two-Phase System

Construct ionic liquid - salt aqueous two-phase system for extracting yeast DNA. By using NaOH solution to process yeast, leaching the nucleic acid by ultrasonic assisting, variety of salts’ aqueous two-phase influence on the ionic liquid 1-butyl-3-methylimidazolium fluoroborate are discussed, and the influence of additive quantity of KH2PO4 and PH on the ionic liquid aqueous two-phase system for extraction of nucleic acid are studied. The result shows that process the yeast with 0.3% NaOH solution, assisted by ultrasound with power of 80W, temperature 60 °C, 3 hours’ extraction. KH2PO4take obvious advantage in the formation of ionic liquid aqueous two-phase system. In the process of extraction nucleic acid from [BMIM] BF4-H2O-KH2PO4aqueous two-phase process of nucleic acid, the best B-R buffer PH is 8.95, when the additive dosage of KH2PO4is 2.000g, A260/A280 in the supernatant is smaller than control group, the substratum which rich in ionic liquid contains more nucleic acid than the supernatant, and A260 in the supernatant is more than that in the control group. Therefore, we conclude that the ionic liquid aqueous two-phase has a relatively good effect in extraction of nucleic.

Design of environmentally friendly ionic liquid aqueous two-phase systems for the efficient and high activity extraction of proteins

Ionic liquids (ILs) have numerous applications in industrial processes as a benign alternative to conventional volatile organic solvents. However, many of them are toxic to organisms and are poorly biodegradable. In this work, a series of environmentally friendly cholinium ILs have been designed and synthesized. It was found that these ILs could form aqueous two-phase systems (ATPSs) with polypropylene glycol 400 (PPG400) which is thermo-sensitive, non-toxic and biodegradable. In order to understand the phase formation processes and possible application of these ATPSs for extraction/separation of proteins, the binodal curves and tie lines of these ATPSs were measured at 25 °C, and the effects of anionic structure of the ionic liquids, nature of the proteins and difference in the concentration of top- and bottom-phases on the partitioning behavior of some typical proteins were investigated systematically. It was shown that bovine serum albumin (BSA), trypsin, papain and lysozyme could be enriched effectively into the ionic liquid-rich phase of the ATPSs, and single-step extraction efficiency could be as high as 86.4–99.9% under the optimized conditions. Furthermore, enzyme activity of the native trypsin in water and in aqueous ionic liquid solutions was determined by using N-a-benzoyl-L-arginine ethyl ester as a substrate, and activity increases to about 127% was observed after 13 months storage. In addition, PPG400 has been recovered simply by heating and reused in the next extraction processes. This avoids the non-sustainable issue of highly salty water produced in the application of the polyethylene glycol (PEG) + salt and ionic liquid + salt ATPSs.

Extraction of Gatifloxacin in Water by Use of Ionic Liquid–Salt Aqueous Two-Phase System

An ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate( [BMIM] BF4) / salt aqueous two-phase systems (ATPS) was presented as a simple, rapid and effective sample pretreatment technique coupled with double-beam UV-Vis spectrophotometer for analysis of gatifloxacin in water. For the purpose to choose optimal conditions, various factors were considered systematically, and the results indicated that the pH value, the salt-out ability of salt and the amount of [BMIM] BF4 had great influence on phase separation and extraction. Under the optimal condition, gatifloxacin in different concentration were enriched and determined, the recovery was 87.3–91.5%.

(Liquid + liquid) equilibrium of (imidazolium ionic liquids + organic salts) aqueous two-phase systems at T = 298.15 K and the influence of salts and ionic liquids on the phase separation

(Liquid + liquid) equilibrium for the {1-ethyl-3-methylimidazolium tetrafluoroborate ([C 2mim]BF 4)/1-propyl-3-methylimidazolium tetrafluoroborate ([C 3mim]BF 4) + organic salt + H 2O} aqueous two-phase systems (ATPSs) have been experimentally ascertained at T = 298.15 K. Three empirical equations were used to correlate the binodal data. On the basis of the empirical equation of the binodal curve with the highest accuracy and lever rule, the (liquid + liquid) equilibrium data were calculated by MATLAB. The reliability of the tie line compositions was proved by the empirical correlation equations given by the Othmer–Tobias and Bancroft equations. The effective excluded volume (EEV) values obtained from the binodal model for these systems were determined. The EEV and the binodal curves plotted in molality both indicate that the salting-out abilities of the four salts follow the order: Na 3C 6H 5O 7 > (NH 4) 3C 6H 5O 7 > Na 2C 4H 4O 4 ≈ Na 2C 4H 4O 6, while the phase-separation abilities of the investigated ILs are in the order of [C 3mim]BF 4 > [C 2mim]BF 4. In the systems investigated, the effect of salts on the phase-forming capability was also evaluated in the shape of the salting-out coefficient obtained from fitting the tie-line data to a Setschenow-type equation. The phase-forming ability increases with the increase of salting-out coefficient.

Application of Water-Miscible Alcohol-Based Aqueous Two-Phase Systems for Extraction of Dyes

The water-miscible alcohols (ethanol, 1-propanpol, 2-propanol) were used to form aqueous two-phase systems with K2HPO4 and Na2HPO4. Meanwhile, the organic citrates were also investigated as the phase-separation salts. The effects of the types and concentrations of phase-forming substances as well as temperature on the formation of aqueous two-phase systems were discussed. The alcohol (ethanol, 1-propanpol, 2-propanol)–salt (K2HPO4, K3C6H5O7, (NH4)3C6H5O7) aqueous two-phase systems were used to extract Rhodamine B and methyl orange in aqueous solution. It proved that the water-miscible alcohol–salt (inorganic salt, organic salt) aqueous two-phase systems can be both used to extract hydrophilic targets directly without adding any reaction reagents. The aqueous two-phase extraction process was also discussed.

Extraction mechanism of sulfamethoxazole in water samples using aqueous two-phase systems of poly(propylene glycol) and salt

Based on the poly(propylene glycol) 400 (PPG 400)–salt aqueous two-phase system (ATPS), a green, economical and effective sample pretreatment technique coupled with high performance liquid chromatography was proposed for the separation and determination of sulfamethoxazole (SMX). The extraction yield of SMX in PPG 400–salt ATPS is influenced by various factors, including the salt species, the amount of salt, pH, and the temperature. Under the optimum conditions, most of SMX was partitioning into the polymer-rich phase with the average extraction efficiency of 99.2%, which may be attributed to the hydrophobic interaction and salting-out effect. This extraction technique has been successfully applied to the analysis of SMX in real water samples with the recoveries of 96.0–100.6%, the detection limits of 0.1 μg L −1, and the linear ranges of 2.5–250.0 μg L −1.

Partition behavior and partition mechanism of antibiotics in ethanol/2-propanol–ammonium sulfate aqueous two-phase systems

In this paper, the feasibility of applying the water-miscible alcohol–salt aqueous two-phase system to separate small molecular antibiotics in aqueous solution was proved. The partition behavior of tetracycline hydrochloride in the ethanol/2-propanol–(NH 4) 2SO 4 aqueous two-phase system was investigated by determining partition coefficients and extraction efficiency. The partition coefficient and extraction efficiency of tetracycline hydrochloride in the ethanol–(NH 4) 2SO 4 ATPS could reach 12.51% and 75.77% respectively at pH 2.00 and 0.50 g/mL (NH 4) 2SO 4, furthermore, that of tetracycline hydrochloride in the 2-propanol–(NH 4) 2SO 4 ATPS could reach 30.03% and 87.70% respectively at pH 1.52 and 0.50 g/mL (NH 4) 2SO 4. The target was found to partition preferentially into the alcohol-rich phase in its cation form at pH < 4.0. The effects of the concentration of salt, the type of alcohol, pH and temperature were discussed in detail. The partition of target to the top phase was enhanced by decreasing pH from its isoelectric point of 5.4 and increasing the concentration of salt and temperature. Another objective of this study was to discuss the underlying mechanism governing the uneven partition of target and phase-separation. The experimental phenomenon and results both indicate that the salting-out effect of salt is the driving force for the uneven partition of target, so the salting-out effect of salts on the separation of target cannot be neglected in discussing aqueous two-phase extraction mechanism.

A descriptive model and methods for up-scaled process routes for interfacial partition of bioparticles in aqueous two-phase systems

In this paper, we have developed a descriptive model and methods for the up-scaled interfacial partition of bioparticles in polymer–salt aqueous two-phase systems (ATPS). The model is only valid for ideal spherical particles. The model might shed some light on the mechanism of interfacial partition, which allows one to draft some process routes for its potential operation on a larger scale.

Solute partitioning in polymer–salt ATPS: The Collander equation

The partition coefficients for several solutes (five nitrophenylated-monosaccharides and four proteins) were experimentally determined, at 23 °C, in three different tie-lines of two polymer–salt aqueous two-phase systems (ATPS): UCON-K 2HPO 4 and UCON-NaH 2PO 4. These partition coefficients together with others obtained from the literature for five dinitrophenylated-amino acids were used to investigate the suitability of the Collander equation to correlate partition coefficients in polymer–salt ATPS. This equation was first proposed to describe the linear correlation between partition coefficients of solutes in different water–organic solvent systems. More recently, it was proved that partition coefficients for several biomolecules in polymer–polymer ATPS can also be correlated with this equation. In this work, several correlations were tested: partition coefficients obtained for different tie-lines within the same system and also partition coefficients obtained from different systems. In both cases, a linear relation was observed, despite a less satisfactory correlation was found when different ATPS were compared. Overall, it was demonstrated that the Collander equation can be used to satisfactorily correlate solute partitioning in the studied polymer–salt ATPS.

(Liquid+liquid) equilibria for (acetate-based ionic liquids+inorganic salts) aqueous two-phase systems

In the present work, (liquid + liquid) equilibrium data have been determined experimentally for aqueous two-phase systems formed by the imidazolium ionic liquids of [Cnmim][CH3COO] (n = 4, 6, 8) and inorganic salts of K3PO4, K2HPO4, and K2CO3 at T = 298.15 K. Combined with available data in the literature, the effect of alkyl chain length of cations, type of anions of the ionic liquids, and nature of the inorganic salts were examined on the binodal curves of the systems. Then the binodal curves were fitted to a four-parameter empirical equation, and the tie-lines were described by the Othmer–Tobias and Bancroft equations. In addition, the extraction capacity of the {[Cnmim][CH3COO] (n = 4, 6, 8) + K3PO4} aqueous two-phase systems was evaluated through their application to the extraction of l-tryptophan. The high extraction efficiency suggests that these aqueous two-phase systems are feasible to be used in the extraction and separation process.

Partitioning of l-Lysine Monohydrochloride in Aqueous Two-Phase Systems of Poly(ethylene glycol) and Dipotassium Hydrogen Phosphate or Trisodium Citrate 5-Hydrate

The partition constants of l-lysine HCl were measured in polymer−salt aqueous two-phase systems. These systems contain poly(ethylene glycol) with a nominal molecular weight of 4000 or 10000 and two different salts (dipotassium hydrogen phosphate or trisodium citrate 5-hydrate). The experimental data were obtained at temperatures of (293.15, 298.15, and 303.15) K. The effects of temperature, pH, polymer and salt concentrations, polymer molecular weight, and salt type on the partitioning of l-lysine HCl were also studied. The results showed that salt concentration has a significant effect on the partition constant while temperature has less effect. The Diamond and Hsu model was used to correlate the experimental partition constants of l-lysine HCl.

Phase equilibrium and macrolide antibiotics partitioning in real water samples using a two-phase system composed of the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate and an aqueous solution of an inorganic salt

An ionic liquid-salt aqueous two-phase system (ILATPS) based on the hydrophilic ionic liquid 1-butyl-3- methylimidazolium tetrafluoroborate ((Bmim)BF4) and inor- ganic salt was developed for direct separation and analysis of macrolide antibiotics coupled with molecular fluorescence spectrophotometry. Liquid-liquid equilibria of (Bmim)BF4- salt aqueous two-phase systems were studied for different salts and temperatures. It was found that the salting-out ability of different salts may be related to the Gibbs energy of hydration of the ions, and the two-phase area was expanded with a decrease in temperature. The partition coefficients as well as extraction efficiencies of azithromycin and mydecamycin in (Bmim)BF4-salt aqueous two-phase system were influenced by the types of salts, concentration of salt, and the extracting temperature. Under the optimum conditions, the average partition coefficient of azithromycin in (Bmim)BF4-Na2CO3 ILATPS was 162, and that of mydecamycin in (Bmim)BF4 -N aH2PO4 ILATPS was 90.9. This method has been satisfactorily applied to the determi- nation of azithromycin and mydecamycin in real water samples with detection limits of 0.059 µg mL −1 and 0.019 µg mL −1 . This extraction method is a simple, non- toxic and effective sample pretreatment technique with promise also for the separation of other small biomolecules.

Measurement of partition coefficients of β-amylase and amyloglucosidase enzymes in aqueous two-phase systems containing poly(ethylene glycol) and Na 2SO 4/KH 2PO 4 at different temperatures

In this research, partitioning of β-amylase and amyloglucosidase was investigated in polymer–salt aqueous two-phase systems containing poly(ethylene glycol) (PEG) with different molecular weights such as 4000, 6000 and 10,000 and Na 2SO 4 or KH 2PO 4. The experimental partition coefficients were measured at T = (298.5, 301.5, 303.5, 305.5 and 308) K. The results showed that the concentration of salt in feed had more effect on partition coefficients of β-amylase and amyloglucosidase in aqueous two-phase systems than the concentration of polymer in initial feed. Also, the results indicated that temperature had a small effect on partitioning of β-amylase and amyloglucosidase enzymes. The partition coefficients of β-amylase and amyloglucosidase in polymer–salt aqueous two-phase systems were correlated using the UNIFAC-FV group contribution model.