Ionic liquids as additives to enhance the extraction of antioxidants in aqueous two-phase systems

Deep Eutectic Solvent-Based Aqueous Two-Phase Systems and Their Application in Partitioning of Phenol Compounds

This work studies the partition of phenolic compounds, namely caffeic acid, syringic acid, vanillic acid, ferulic acid, and vanillin, in aqueous two-phase systems (ATPSs) formed by acetonitrile and deep eutectic solvents (DESs) based on choline chloride ([Ch]Cl) and carbohydrates (sucrose, d-glucose, d-mannose, arabinose, and d-xylose). The binodal curves built at 25 °C and 0.1 MPa using DES were compared with ATPS composed of [Ch]Cl and the same carbohydrates. The ability to form ATPS depends on the number and kind of hydroxyl groups in DES's hydrogen-bond donor compound (carbohydrates). ATPS based on DES showed biphasic regions larger than the systems based on [Ch]Cl and carbohydrates alone due to the larger hydrophilicity of DES. The ATPS were used to study the partition of the phenolic compounds. For all the systems, the biomolecules preferentially partitioned to the acetonitrile-rich phase (K > 1), and the best recovery in the top phase ranged between 53.36% (caffeic acid) and 90.09% (vanillin). According to the remarkable results, DES-based ATPS can selectively separate ferulic acid and vanillin for the top phase and syringic, caffeic, and vanillic acids for the bottom phase, achieving a selectivity higher than two.

Extraction of phenolic compounds from walnut green husk (Juglans regia L.) by Salting-Out extraction method

Some factors in the salting-out extraction (SOE) method play a major role. The aim of this study was to investigate the interaction effects of the phase forming components and consequently select the best conditions to achieve a highly efficient recovery of phenolic compounds from walnut green husks (Juglans regia L.) using mixtures of ethanol and aqueous ammonium sulfate solutions. According to the results that were analyzed by response surface methodology, the optimal extraction conditions were obtained at ethanol: salt: water ratio of 34.8: 15.1: 54.4 (w/w) at a pH of 6-6.5 and 25 °C. At the optimal conditions, the overall phenolic and flavonoid content, and antioxidant activity were significantly higher than obtained by the conventional method. In addition, at a higher scale (i.e., 5 kg), similar results were obtained. Thus, it can be concluded that SOE has the potential to be scaled up for the simultaneous separation and purification of compounds from plant biomass. This paper is addressing extraction techniques, measurement, and characterization of new natural phenolic compounds from an agricultural by-product and valorization of waste.

Study on Extraction and Purification of Acanthopanax senticosus Polyphenols by an Ionic Liquid-Assisted Aqueous Two-Phase System

This study aimed to extract and purify polyphenols from Acanthopanax senticosus. A new green method was developed, in which ionic liquids (ILs) were used as aqueous two-phase (ATP) adjuvants to extract the polyphenols from A. senticosus. An ionic liquid-assisted aqueous two-phase system (IL-ATPS) was established. The purification of the polyphenols from the extraction fluid by AB-8 macroporous resin was conducted, and the kinetic mechanisms were studied. The reuse of ionic liquids was executed. The results showed that an [OMIM]Br-assisted ethanol/NaH2PO4 system (IL-ATPS) was the best extraction solvent. In this study, the following optimal extraction conditions were determined: 32 wt.% ethanol, 25 wt.% NaH2PO4, 9 wt.% additional ionic liquid, a solid-liquid ratio of 1:40 g/mL, an extraction temperature of 50 °C, a pH of 4.0, an extraction time of 50 min, and an extraction rate of the polyphenols at 15.90 mg/g. The optimum adsorption parameters of the macroporous resin AB-8 were as follows: a flow rate of 3.5 BV·h-1, a sample volume of 40 mL, an elution flow rate of 3.5 BV·h-1, an eluent volume of 80 mL, and an eluant that was constituted by an 85% volume fraction of ethanol. The decolorization effect of 4% activated carbon was better than the other amounts; in addition, a decolorization rate of 76.81% and an ionic liquid recovery rate of 81.12% were found to be the most optimal. Compared with the traditional extraction methods, IL-ATPS has the advantages of requiring simple operation, saving time, and high efficiency. In addition, it can be used for the extraction of the polyphenolic compounds.

Aqueous Two-Phase Systems Based on Ionic Liquids and Deep Eutectic Solvents as a Tool for the Recovery of Non-Protein Bioactive Compounds—A Review

Aqueous two-phase systems (ATPS) based on ionic liquids (IL) and deep eutectic solvents (DES) are ecofriendly choices and can be used to selectively separate compounds of interest, such as bioactive compounds. Bioactive compounds are nutrients and nonnutrients of animal, plant, and microbial origin that benefit the human body in addition to their classic nutritional properties. They can also be used for technical purposes in food and as active components in the chemical and pharmaceutical industries. Because they are usually present in complex matrices and low concentrations, it is necessary to separate them in order to increase their availability and stability, and ATPS is a highlighted technique for this purpose. This review demonstrates the application of ATPS based on IL and DES as a tool for recovering nonprotein bioactive compounds, considering critical factors, results and the most recent advances in this field. In addition, the review emphasizes the perspectives for expanding the use of nonconventional ATPS in purification systems, which consider the use of molecular modelling to predict experimental conditions, the investigation of diverse compounds in phase-forming systems, the establishment of optimal operational parameters, and the verification of bioactivities after the purification process.

Selective Partition of Lipopeptides from Fermentation Broth: A Green and Sustainable Approach

Lipopeptide (LP) biosurfactants from microbes have the potential to gradually replace chemical synthetic surfactants and fit the contemporary green and sustainable industrial production concept. However, their active participation is comparatively low in the global market pertaining to their low yield in microbial broth and costly downstream processes arising due to tedious isolation and purification methods. Herein, an efficient extraction method is developed that utilizes an aqueous biphasic system (ABS) comprising ionic liquids and polypropylene glycol 400 (PPG) to selectively extract a mixture of cyclic lipopeptides, namely, surfactin and fengycin from the culture broth of Bacillus amyloliquefaciens 5NPA-1, isolated from the halophyte Salicornia brachiata Roxb. Out of four different ABSs, the ABS composed of 2-hydroxyethyl ammonium formate and PPG displayed a maximum extraction efficiency of 82.30%. PPG-rich phase containing lipopeptides exhibited excellent antimicrobial and mosquito larvicidal properties with no toxic effect on plants. The developed method is simple, novel and accelerates the application of cyclic lipopeptides produced by the microbial source.

Separation of Albumin from Bovine Serum Applying Ionic-Liquid-Based Aqueous Biphasic Systems

In this work, the extraction and separation of bovine serum albumin (BSA) from its original matrix, i.e., bovine serum, was performed using a novel ionic-liquid-based aqueous biphasic system (IL-based ABS). To this end, imidazolium-, phosphonium-, and ammonium-based ILs, combined with the anions’ acetate, arginate and derived from Good Buffers, were synthesized, characterized, and applied in the development of ABS with K2HPO4/KH2PO4 buffer aqueous solutions at pH 7. Initial studies with commercial BSA revealed a preferential migration of the protein to the IL-rich phase, with extraction efficiencies of 100% obtained in a single-step. BSA recovery yields ranging between 64.0% and 84.9% were achieved, with the system comprising the IL tetrabutylammonium acetate leading to the maximum recovery yield. With this IL, BSA was directly extracted and separated from bovine serum using the respective ABS. Different serum dilutions were further investigated to improve the separation performance. Under the best identified conditions, BSA can be extracted from bovine serum with a recovery yield of 85.6% and a purity of 61.2%. Moreover, it is shown that the BSA secondary structure is maintained in the extraction process, i.e., after being extracted to the IL-rich phase. Overall, the new ABS herein proposed may be used as an alternative platform for the purification of BSA from serum samples and can be applied to other added-value proteins.

Assessing the hydrotropic effect in the presence of electrolytes: competition between solute salting-out and salt-induced hydrotrope aggregation

Water solubility enhancement is a long-standing challenge in a multitude of chemistry-related fields. Hydrotropy is a simple and efficient method to improve the solubility of hydrophobic molecules in aqueous media....

Characterization of alcohol/salt aqueous two-phase system for optimal separation of gallic acids

Gallic acid (GA) is a hydrophilic polyphenol which is noteworthy for strong antioxidant capacity. The drawbacks of conventional extraction approaches such as time-consuming and high processing cost are often viewed as a hurdle to extract GA from plant sources in industrial scale. Aqueous two-phase system (ATPS) is a separation approach which can be employed as an alternative to the conventional approaches. The partition behaviour of GA in an alcohol/salt ATPS was investigated in this study to aid the development of industrial scale ATPS to extract GA from natural sources. The separation of GA was characterized by determining the types of alcohol and salt, phase composition, sample load, pH of the system and addition of adjuvants applied in the alcohol/salt ATPS construction. The hydrophilic GA was targeted to the salt-rich phase of the alcohol/salt ATPS with a partition coefficient (K_GA) of 25.00 ± 0.00. The optimum condition of ATPS for the maximum partition of GA was achieved in ATPS comprised of 24% (w/w) 1-propanol and 22% (w/w) phosphate salt at pH 8 with 5% (w/w) of 1 mg/mL sample loading and 2% (w/w) NaCl addition. The findings suggest that ATPS can be applied for separation of GA from various natural sources.

Nucleophilic degradation of diazinon in thermoreversible polymer-polymer aqueous biphasic systems

Although aqueous biphasic systems have been largely investigated in the separation and/or purification of biocompounds, their potential as reaction media to design integrated reaction-separation processes has been less explored. In this work aqueous biphasic systems (ABSs) composed of polypropylene glycol of molecular weight 400 g mol-1 (PPG 400) and different polyethylene glycols (PEGs) were characterized, and investigated for integrated reaction-separation processes, i.e. in the nucleophilic degradation of diazinon and further separation of reaction products by taking advantage of the lower-critical solution temperature (LCST) behaviour of these ABSs. The nucleophilic degradation of diazinon was carried out in the monophasic regime at 298 K, after which an increase in temperature (up to 313 K) allowed the product separation by two-phase formation (thermoreversible systems). The reaction kinetics and reaction pathways have been determined. The reaction kinetic increases as the PEG molecular weight decreases, with the half-life values obtained being competitive to those previously reported using volatile organic solvents as solvent media and significantly higher than under alkaline hydrolysis. One reaction pathway occurs in ABSs comprising PEGs of higher molecular weights, whereas in the ABS composed of PEG 600 two reaction pathways have been identified, meaning that the reaction pathways can be tailored by changing the PEG nature. ABSs formed by PEGs of lower molecular weights were identified as the most promising option to separate the pesticide degradation products by simply applying changes in temperature.

Aqueous two-phase systems as a tool for bioseparation – emphasis on organic acids

Aqueous two-phase systems (ATPS) are universally recognized as an excellent alternative to the conventional separation techniques in the biotechnology, because of their undoubted advantages such as mild and biocompatible conditions, high water content, low interfacial tension, ease of process integration and scale up, etc. The formation of ATPS is due to the incompatibility of two polymers in a common solution. Other types of ATPS are formed by polymer/salt, ionic and/or non-ionic surfactants, inorganic salt/short-chain alcohols, and based on room temperature ionic liquids. ATPS are successfully used (even in large scale) for cells, enzyme and protein separation, while their application for recovery of small molecules such as organic acids, antibiotics, alcohols is more complicated as they are usually hydrophilic and tend to distribute evenly between the phases. The purpose of this paper is to overview and summarize the efforts made for the application of different types of ATPS for the separation of organic acids.

Oenin/Syringic Acid Copigmentation: Insights From a Theoretical Study

On the basis of the dispersion-corrected density functional theory, a computational model is proposed to describe the oenin/syringic acid copigmentation and to explore the non-covalent interaction between the anthocyanin and the copigment in the framework of implicit solvent approach. The predicted binding free energy and visible spectrum shift of this copigmentation complex are in accordance with the experimental observations. The used model provides a good structural description of oenin/syringic acid complex and suggests that the intermolecular hydrogen bonding, in which the hydroxyl-rich sugar moiety in oenin plays a key role, may be the determinant for the formation and nature of the copigmentation complex.

Ionic Liquid Aqueous Two-Phase Systems From a Pharmaceutical Perspective

Aqueous Two-Phase Systems (ATPSs) have been extensively studied for their ability to simultaneously separate and purify active pharmaceutical ingredients (APIs) and key intermediates with high yields and high purity. Depending on the ATPS composition, it can be adapted for the separation and purification of cells, nucleic acids, proteins, antibodies, and small molecules. This method has been shown to be scalable, allowing it to be used in the milliliter scale for early drug development to thousands of liters in manufacture for commercial supply. The benefits of ATPS in pharmaceutical separations is increasingly being recognized and investigated by larger pharmaceutical companies. ATPSs use identical instrumentation and similar methodology, therefore a change from traditional methods has a theoretical low barrier of adoption. The cost of typical components used to form an ATPS at large scale, particularly that of polymer-polymer systems, is the primary challenge to widespread use across industry. However, there are a few polymer-salt examples where the increase in yield at commercial scale justifies the cost of using ATPSs for macromolecule purification. More recently, Ionic Liquids (ILs) have been used for ATPS separations that is more sustainable as a solvent, and more economical than polymers often used in ATPSs for small molecule applications. Such IL-ATPSs still retain much of the attractive characteristics such as customizable chemical and physical properties, stability, safety, and most importantly, can provide higher yield separations of organic compounds, and efficient solvent recycling to lower financial and environmental costs of large scale manufacturing.

Determination of Heavy Metal Ions and Organic Pollutants in Water Samples Using Ionic Liquids and Ionic Liquid-Modified Sorbents

Water pollution, especially by inorganic and organic substances, is considered as a critical problem worldwide. Several governmental agencies are listing an increasing number of compounds as serious problems in water because of their toxicity, bioaccumulation, and persistence. In recent decades, there has been considerable research on developing analytical methods of heavy metal ions and organic pollutants from water. Ionic liquids, as the environment-friendly solvents, have been applied in the analytical process owing to their unique physicochemical properties. This review summarizes the applications of ionic liquids in the determination of heavy metal ions and organic pollutants in water samples. In addition, some sorbents that were modified physically or chemically by ionic liquids were applied in the adsorption of pollutants. According to the results in all references, the application of new designed ionic liquids and related sorbents is expected to increase in the future.

Understanding the Effect of Ionic Liquids as Adjuvants in the Partition of Biomolecules in Aqueous Two-Phase Systems Formed by Polymers and Weak Salting-Out Agents

Ionic liquids (ILs) as adjuvants in polymer-salt aqueous two-phase systems (ATPS) have been used to improve the extraction of biomolecules. However, the impact of ILs as adjuvants on the partition of biomolecules is still poorly understood. Previous works mostly focused on ATPS based on strong salting-out agents, which may mask the IL effect. In this work, ATPS formed by polyethylene glycol (PEG 400) and a weak salting-out salt ((NH₄)₂SO₄) with a wide number of ILs as adjuvants (chloride-based combined with cholinium, imidazolium, pyrrolidinium, piperidinium, tetralkylammonium and tetralkylphosphonium cations) were investigated. The respective phase diagrams were determined, and the systems extraction performance for a wide range of biomolecules (phenolic compounds, alkaloids and amino acids) was investigated. The results obtained show that ILs as adjuvants in polymer-salt ATPS modulate the partition of biomolecules. In particular, more hydrophobic ILs significantly enhance the partition of more hydrophobic biomolecules to the PEG-rich phase (where the IL is enriched). Furthermore, the intensity of the IL effect is more pronounced when using weak salting-out agents. A linear correlation between the biomolecules and the ILs partition coefficients, and with the biomolecules octanol-water partition coefficients, was found. In most ATPS formed by polymers and salts using ILs as adjuvants, the biomolecules partition is driven by the ILs partition and by the difference in hydrophobicity between the coexisting phases.

Optimization of purification conditions for papain in a polyethylene glycol-phosphate aqueous two-phase system using quaternary ammonium ionic liquids as adjuvants by BBD-RSM

This work attempts to study and optimize the conditions for separating and purifying papain in aqueous two-phase systems (ATPSs). Quaternary ammonium ionic liquids (ILs, 4 wt%) were added as adjuvants to a PEG-phosphate ATPS. On the basis of single-factor experiments, a Box-Behnken design with response surface methodology (BBD-RSM) was used to optimize the purification conditions of papain in the ATPS by setting the NaH₂PO₄·2H₂O concentration, PEG concentration and pH as independent variables and the overall desirability (OD) of the recovery rate of papain, the protein recovery rate and the purification factor as dependent variables. The following optimum conditions were determined: PEG4000 16.4 wt%, NaH₂PO₄·2H₂O 13.7 wt%, pH 6.22, temperature 60 °C and enzyme concentration 12.0 mg/ml. Under the optimized conditions, the purification factor for the ATPS supplemented with commercial enzyme increased from 1.331 (no ILs) to 3.380 (containing 4 wt% [N₂₂₂₂]BF₄). The total evaluation OD was 0.9979, the maximum predicted OD was 0.9994, and the deviation rate was -0.15%. Therefore, the model established in this experiment could predict the experimental value well. To verify the practical effect of the model, papain obtained from fresh papaya latex (papain crude extract) was applied to the same ATPS. The results showed that the purification factor of the ATPS with papain crude extract increased from 3.517 (no ILs) to 12.04 (containing 4 wt% [N₂₂₂₂]BF₄). In summary, the addition of 4 wt% ILs to partially replace PEG greatly improved the purification factor for crude papain extract enriched in the phosphate phase, providing a potential method for the large-scale industrial production of papain.

Extraction of ferulic acid and vanilla acid by hydrophobic ionic liquid 1-hexyl-3-methylimidazolium hexafluorophosphate

The study was carried out to evaluate the extraction efficiency of ferulic acid (FA) and vanilla acid (VA) from aqueous phase into IL phase. To achieve the highest extraction efficiency, the influence of varying key parameters was evaluated and optimized by response surface methodology based on Box-Behnken design, including phase volume ratio, extraction temperature and extraction time. FA (or VA) extraction under the optimal conditions were: phase volume ratio of 1.38 (1.28), extraction temperature of 66.34 °C (49.28 °C) and extraction time of 33.83 min (36.64 min) under optimum conditions an average extraction efficiency of 97.11 ± 1.05% for FA was achieved, while VA was 85.43 ± 1.62%. This was very close to the predicted value from the model, 98.05% (86.16%). Additionally, recycling and utilization of ILs were performed well with the recovery ratio for 81.0%. Based on thermodynamic analysis, FTIR and ¹H NMR analysis, the combination of hydrophobic interaction and hydrogen-bond interaction resulted in the real extraction result above. It is desirable to provide a useful reference for the separation and purification of FA, VA, and extend the potential application of ionic liquid in the separation of natural active compounds with great prospects.

Enhanced separation performance of aqueous biphasic systems formed by carbohydrates and tetraalkylphosphonium- or tetraalkylammonium-based ionic liquids

Aiming at establishing more effective and sustainable separation processes, herein we propose the use of carbohydrates combined with tetralkylphosphonium- and tetralkylammonium-based ionic liquids (ILs) to form aqueous biphasic systems (ABS). The formation of ABS composed of non-aromatic and non-fluorinated ILs with carbohydrates is here shown for the first time. These novel systems are competive extraction platforms when compared against more conventional ABS formed by ILs and salts or fluorinated ILs and carbohydrates. Finally, it is shown that these systems can be efficiently recovered and reused.

Potential of Aqueous Two-Phase Systems for the Separation of Levodopa from Similar Biomolecules

BACKGROUND

Levodopa is a precursor of several neurotransmitters, such as dopamine, and is used in the treatment of the Parkinson's disease. In this work, an alternative strategy was studied to separate levodopa from similar biomolecules using aqueous two-phase systems (ATPS).

RESULTS

Ternary ATPS composed of polyethylene glycol (PEG) 400 or ionic liquids (ILs), citrate buffer (K3C6H5O7/C6H8O7) at pH 7.0 and water, and quaternary ATPS composed of PEG 400, K3C6H5O7/C6H8O7 at pH 7.0, water and the same ILs at 5 wt%, were studied. The respective liquid-liquid phase diagrams were determined at 298 K to appraise the mixture compositions required to form two-phase systems, followed by studies of the partition of levodopa and structurally similar biomolecules (dopamine, L-phenylalanine, and L-tyrosine). Their partition coefficients and extraction efficiencies have been determined, and the selectivity of the ATPS to separate levodopa from the remaining biomolecules evaluated.

CONCLUSION

The results obtained indicated that PEG-based ATPS were the most effective to separate levodopa from L-phenylalanine while the separation from the other biomolecules was better using IL-based ATPS, in particular those based on [P4444]Cl and [N4444]Cl, with extraction efficiencies of levodopa to the salt-rich phase ranging between 62.7 and 74.0%, and of the remaining biomolecules to polymer/IL-rich phase up to 91.5%.

The role of ionic liquid [C4 C1 im]Br as an adjuvant on the two-phase formation and the extraction of l-phenylalanine in ABS composed of PEG400 and potassium citrate at different temperatures

The potential of {polyethylene glycol 400 + potassium citrate} aqueous biphasic system (ABS) with ionic liquid (IL) 1-butyl-3-methylimidazolium bromide ([C₄ C₁ im]Br) as an adjuvant is examined for the extraction of l-phenylalanine (Phe), as a model biomolecule, at different temperatures and system compositions. The binodal curves and liquid-liquid equilibrium data were determined by the addition of 5 wt% IL to investigate its effect on phase diagrams and Phe partition coefficients. The results indicate that binodal curves of systems with and without IL are more deviated from each other with decreasing temperature. Moreover, IL has a high tendency to partition into the PEG-rich phase. This tendency increases with increasing temperature and system compositions. For Phe, the partition coefficients obtained in this work (K_Phe ≈ 5.5-81.2) are significantly higher than those observed in other conventional PEG-inorganic salt ABS (K_Phe ≈ 0.5-2.5), water-immiscible ILs two-phase extraction systems (K_Phe ≈ 0.02-1.2), or even, in the IL-based ABS with the same IL as the main phase-forming component (K_Phe ≈ 3.2). The phase hydrophobicity, salting-out and π⋯π stacking seem to be the main driving forces to affect the extraction aptitude of the studied ABS for Phe. Furthermore, the performance of using [C₄ C₁ im]Br as adjuvant to improve the partition of Phe in the studied ABS at different temperatures seems to be ruled by the differences in the phases hydrophobicities. Finally, the experimental tie lines and partition coefficients are accurately correlated using the NRTL model. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 2018 © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 34:1149-1166, 2018.

Emerging Biotechnology Applications of Aqueous Two-Phase Systems

Liquid-liquid phase separation between aqueous solutions containing two incompatible polymers, a polymer and a salt, or a polymer and a surfactant, has been exploited for a wide variety of biotechnology applications throughout the years. While many applications for aqueous two-phase systems fall within the realm of separation science, the ability to partition many different materials within these systems, coupled with recent advances in materials science and liquid handling, has allowed bioengineers to imagine new applications. This progress report provides an overview of the history and key properties of aqueous two-phase systems to lend context to how these materials have progressed to modern applications such as cellular micropatterning and bioprinting, high-throughput 3D tissue assembly, microscale biomolecular assay development, facilitation of cell separation and microcapsule production using microfluidic devices, and synthetic biology. Future directions and present limitations and design considerations of this adaptable and promising toolkit for biomolecule and cellular manipulation are further evaluated.