IL-based Aqueous Two-phase Systems Research Articles

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

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). 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. 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%.

Effect of salt-based adjuvant on partition behaviour of protein in aqueous two-phase systems composed of polypropylene glycol and cholinium glycinate

Abstract Aqueous two-phase systems (ATPSs) composed of ionic liquids (ILs) have been widely explored over the past decade for application in protein purification. The interaction between the phase components of ATPSs and the target protein is one of the factors governing the partition behaviour of the protein. The addition of adjuvants like inorganic salts at a low concentration in an ATPS could manipulate the partitioning of the protein between phases. In this study, the partitioning behaviour of model proteins in ATPSs composed of cholinium glycinate, poly(propylene) glycol 400 and a salt-based adjuvant (i.e., sodium chloride, magnesium chloride and sodium sulfate) was investigated systematically. The dissociated ions with a greater hydration capacity preferentially partitioned to the phase having a higher water content. Also, the partition coefficient of the dissociated ions was independent of the concentration of salt adjuvant. The affinity of adjuvant ions for the IL-rich bottom phase was in the decreasing order of: sulfate ion > chloride ion > magnesium ion > sodium ion. This non-uniform distribution of cations and anions of ionic adjuvants in the ATPS had an influence of the partitioning of proteins in ATPS. Bovine serum albumin and lysozyme, which differ in isoelectric point and surface charge density, were used as the model proteins. The partitioning behaviour of the proteins was affected by the distribution of the dissociated ions of the ionic adjuvant in both phases of the ATPS. The electrostatic interaction between proteins and the dissociated ions of the ionic adjuvant was governed by factors such as types and charge density of the dissociated ions of the salt-based adjuvants, isoelectric point of the protein, and pH of the ATPS. The results proved the feasibility of manipulating the partitioning of target proteins in ATPSs by using inorganic salts as the adjuvant, which provides a means to improve the protein separation in IL-based ATPSs.

Saccharification of cellulose in the ionic liquids and glucose recovery

High-efficiency hydrolysis of lignocellulose is critical for the production of second-generation bioethanol. In the present work, the acid hydrolysis of cellulose in ionic liquids (ILs) 1-butyl-3-methylimidazolium chloride ([Bmim]Cl), 1-allyl-3-methylimidazolium chloride ([Amim]Cl), and 1-ethyl-3-methylimidazolium chloride ([Emim]Cl), respectively, was investigated and aqueous two-phase systems were constructed by adding salt solutions to ILs to recover glucose from cellulose hydrolyzates in the ILs. The effects of reaction temperature, reaction time and acid consumption on the cellulose hydrolysis efficiencies in the ILs were determined. The optimal cellulose hydrolysis conditions in ILs were found to be [Bmim]Cl, a reaction time of 0.5 h, an acid consumption of 0.25 mL/g (cellulose) and a reaction temperature of 100 °C. The yield of glucose under the optimal hydrolysis conditions reached 92.88%. IL-based aqueous two-phase systems were formed by adding NaOH, K3PO4, or K2HPO4 into the ILs containing glucose or cellulose hydrolyzates, which were able to partition the glucose into the bottom salt-rich phase. Under the optimum condition, 4 vol 50% NaOH or K3PO4 solution was able to partition 90% glucose, resulting in 16 g/L glucose in the salt-rich phase that could be further used for ethanol fermentation.

Optimization of the gallic acid extraction using ionic-liquid-based aqueous two-phase systems

Gallic acid is an interesting natural compound because of its antioxidant, anti-inflammatory, antifungal and antitumor properties. It is present in relatively high concentrations in a number of biomass sources and in industrial wastes from where it could be extracted. Aiming at developing benign and efficient extraction/purification processes for gallic acid, aqueous two-phase systems (ATPS) composed of ionic liquids (ILs) and inorganic salts were investigated. Several combinations of ionic liquids and inorganic salts were studied to understand the influence of the ionic liquid structure and of the pH of the aqueous medium on the gallic acid partitioning. It is here shown that at low pH values the non-charged form of gallic acid (or other phenolic compounds) preferentially migrates for the ionic-liquid-rich phase whereas its conjugate base preferentially partitions for the salt-rich phase. The results indicate that IL-based ATPS can be the basis of new extraction/purification processes of gallic acid from natural matrices, and improved extractions are obtained using acidic aqueous solutions.

Partitioning Behavior of Wastewater Proteins in Some Ionic Liquids-Based Aqueous Two-Phase Systems

The recovery of wastewater proteins is gaining more attention in environmental protection. In the present work, phase diagram of the [Cnmim]X (n = 4, 6, 8; X = Cl and Br) + K2HPO4 aqueous two-phase systems have been determined, and the aqueous two-phase systems have been used to remove bovine serum albumin (BSA), lysozyme, and hemoglobin from the simulated wastewater. The influence of pH value, the composition of the aqueous two-phase systems, and the temperature of the systems on the partitioning of the proteins has been studied. It has been found that 76–100% of the proteins could be extracted into the ionic liquid-rich phase in a single step partition. The partition coefficients of lysozyme slightly increases but those of BSA and hemoglobin decrease with increasing tie line length (TLL). The higher extraction efficiency of the proteins is achieved at the pH value close to their isoelectric point and under higher temperatures. The results indicate that the IL-based aqueous two-phase systems have the potential for the separation of wastewater proteins.

Production and purification of an extracellular lipolytic enzyme using ionic liquid-based aqueous two-phase systems

The ability of ionic liquid-based aqueous two-phase systems (ATPS) to purify lipase produced by fermentation is here evaluated and compared against conventional PEG-based ATPS systems. Four ionic liquids, chosen after screening of a larger number of ionic liquids are evaluated, with the maximum purification and higher recovery being obtained for the systems based on [C8mim]Cl. It is shown that IL-based ATPS have a performance superior to PEG-based ATPS for the purification of this enzyme.

Ionic liquids for two-phase systems and their application for purification, extraction and biocatalysis

The development of biotechnological processes using novel two-phase systems based on molten salts known as ionic liquids (ILs) got into the focus of interest. Many new approaches for the beneficial application of the interesting solvent have been published over the last years. ILs bring beneficial properties compared to organic solvents like nonflammability and nonvolatility. There are two possible ways to use the ILs: first, the hydrophobic ones as a substitute for organic solvents in pure two-phase systems with water and second, the hydrophilic ones in aqueous two-phase systems (ATPS). To effectively utilise IL-based two-phase systems or IL-based ATPS in biotechnology, extensive experimental work is required to gain the optimal system parameters to ensure selective extraction of the product of interest. This review will focus on the most actual findings dealing with the basic driving forces for the target extraction in IL-based ATPS as well as presenting some selected examples for the beneficial application of ILs as a substitute for organic solvents. Besides the research focusing on IL-based two-phase systems, the "green aspect" of ILs, due to their negligible vapour pressure, is widely discussed. We will present the newest results concerning ecotoxicity of ILs to get an overview of the state of the art concerning ILs and their utilisation in novel two-phase systems in biotechnology.

Extraction of vanillin using ionic-liquid-based aqueous two-phase systems

To explore proper extractive solvents and to design an optimized separation process it is highly imperative to understand the molecular-based phenomena governing the solutes partitioning. Moreover, the development of new techniques for the biomolecules separation and purification, while maintaining their functional characteristics unchanged, is still ongoing. Therefore, in this work, the partition coefficients of vanillin, a compound with well-known organoleptic properties, were determined using improved ionic-liquid-based aqueous two-phase systems (ATPS). Three main parameters were evaluated through the vanillin partitioning process: the ionic liquid (IL) cation and anion structure, the temperature of equilibrium and the available concentration of vanillin in the global system. In all systems and conditions tested, vanillin preferentially migrates for the IL-rich phase. In addition, the three studied parameters largely influence the vanillin partitioning. In an attempt to elucidate the thermodynamics of the partitioning process, the standard molar thermodynamic functions of transfer of vanillin were also determined based on the temperature dependence data. These data indicate that the partition of vanillin results from an interplay between enthalpic and entropic contributions where both the IL anion and more complex cations play an essential role. Moreover, viscosities and densities of both aqueous phases were experimentally measured at the mass fraction compositions for which the partition coefficients were determined. The results gathered in this work indicate that IL-based ATPS can be further employed in the extraction and purification of vanillin from different matrices, as confirmed by the large partition coefficients obtained and improved low viscosity systems.