Enhanced extraction of bovine serum albumin with aqueous biphasic systems of phosphonium- and ammonium-based ionic liquids

Do Ionic Liquids Exhibit the Required Characteristics to Dissolve, Extract, Stabilize, and Purify Proteins? Past-Present-Future Assessment

Proteins are highly labile molecules, thus requiring the presence of appropriate solvents and excipients in their liquid milieu to keep their stability and biological activity. In this field, ionic liquids (ILs) have gained momentum in the past years, with a relevant number of works reporting their successful use to dissolve, stabilize, extract, and purify proteins. Different approaches in protein-IL systems have been reported, namely, proteins dissolved in (i) neat ILs, (ii) ILs as co-solvents, (iii) ILs as adjuvants, (iv) ILs as surfactants, (v) ILs as phase-forming components of aqueous biphasic systems, and (vi) IL-polymer-protein/peptide conjugates. Herein, we critically analyze the works published to date and provide a comprehensive understanding of the IL-protein interactions affecting the stability, conformational alteration, unfolding, misfolding, and refolding of proteins while providing directions for future studies in view of imminent applications. Overall, it has been found that the stability or purification of proteins by ILs is bispecific and depends on the structure of both the IL and the protein. The most promising IL-protein systems are identified, which is valuable when foreseeing market applications of ILs, e.g., in "protein packaging" and "detergent applications". Future directions and other possibilities of IL-protein systems in light-harvesting and biotechnology/biomedical applications are discussed.

Combined Use of Ionic Liquid-Based Aqueous Biphasic Systems and Microfluidic Devices for the Detection of Prostate-Specific Antigen

Prostate cancer (PCa) is one of the cancer types that most affects males worldwide and is among the highest contributors to cancer mortality rates. Therefore, there is an urgent need to find strategies to improve the diagnosis of PCa. Microtechnologies have been gaining ground in biomedical devices, with microfluidics and lab-on-chip systems potentially revolutionizing medical diagnostics. In this paper, it is shown that prostate-specific antigen (PSA) can be detected through an immunoassay performed in a microbead-based microfluidic device after being extracted and purified from a serum sample through an aqueous biphasic system (ABS). Given their well-established status as ABS components for successful bioseparations, ionic liquids (ILs) and polymers were used in combination with buffered salts. Using both IL-based and polymer-based ABS, it was demonstrated that it is possible to detect PSA in non-physiological environments. It was concluded that the ABS that performed better in extracting the PSA from serum were those composed of tetrabutylammonium chloride ([N₄₄₄₄]Cl) and tetrabutylphosphonium bromide ([P₄₄₄₄]Br), both combined with phosphate buffer, and constituted by polyethylene glycol with a molecular weight of 1000 g/mol (PEG1000) with citrate buffer. In comparison with the assay with PSA prepared in phosphate-buffered saline (PBS) or human serum in which no ABS-mediated extraction was applied, assays attained lower limits of detection after IL-based ABS-mediated extraction. These results reinforce the potential of this method in future point-of-care (PoC) measurements.

New liquid supports in the development of integrated platforms for the reuse of oxidative enzymes and polydopamine production

Polydopamine (PDA), a bioinspired polymer from mussel adhesive proteins, has attracted impressive attention as a novel coating for (nano) materials with an adequate conformal layer and adjustable thickness. Currently, PDA is obtained from dopamine chemical oxidation under alkaline conditions, limiting its use in materials sensible to alkaline environments. Envisaging a widespread use of PDA, the polymerization of dopamine by enzymatic catalysis allows the dopamine polymerization in a large range of pHs, overcoming thus the limitations of conventional chemical oxidation. Moreover, the conventional method of polymerization is a time-consuming process and produces PDA films with poor stability, which restricts its applications. On the other hand, the main bottleneck of enzyme-based biocatalytic processes is the high cost of the single use of the enzyme. In this work, laccase was used to catalyse dopamine polymerization. To improve its performance, a liquid support for integrating the laccase and its reuse together with the PDA production and recovery was developed using aqueous biphasic systems (ABS). Firstly, dopamine polymerization by laccase was optimized in terms of pH, temperature and initial dopamine concentration. It was demonstrated that the highest enzymatic polymerization of dopamine was achieved at pH 5.5, 30°C and 2 mg ml−1 of dopamine. Then, ABS composed of polymers, salts and ionic liquids were evaluated to optimize the laccase confinement in one phase while PDA is recovered in the opposite phase. The most promising ABS allowing the separation of laccase from the reaction product is composed of polypropylene glycol (400 g mol−1) and K2HPO4. The polymerization of dopamine in ABS leads to a remarkable improvement of polymerization of 3.9-fold in comparison to the conventional chemical PDA polymerization. The phase containing the confined laccase was reused for four consecutive reaction cycles, with a relative polymerization of 68.9% in the last cycle. The results of this work proved that ABS are a promising approach to create a liquid support for enzyme reuse allowing the process intensification efforts. The use of biocatalysts in ABS emerges as sustainable and alternative platforms from environmental and techno-economic points of view.

Insights into protein-ionic liquid interaction: A comprehensive overview on theoretical and experimental approaches

Owing to highly tunable nature, ionic liquids are nesting stance in the scientific community for a wide variety of applications ranging from electrochemistry to product purification, from chemical and biomedical applications to biotechnological interventions and proteomics. Proteins are unstable in its native form and several attempts have been made to stabilize them by addition of various additives. This review focusses on the studies conducted to improve protein stability with ionic liquids along with an emphasis on the mechanism of interaction. This review also specifies and discusses about the brief introduction to ionic liquids, evolution of first-, second-, and third generation of liquids over the years and their selection criterion and applications. Though, there are several elegant reviews available on proteins-ionic liquids interaction, this review systematically highlights the effect of ionic liquids viz., imidazolium, ammonium, phosphonium and choline-based ionic liquids (amino acid-based anions & classical anions) on fibrous proteins viz., collagen and keratin and globular proteins viz., bovine serum albumin and cytochrome c. Thus, this review elaborates the thorough investigations conducted to explore the stabilizing properties of ionic liquids over fibrous and globular proteins.

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.

Extraction behaviors of aqueous PEG impregnated resin system in terms of impregnation stability and recovery via protein impregnated resin interactions on bovine serum albumin

Background

Current advances in biotechnology have been looked at as alternative approaches towards the limited product recovery due to time- and cost-consuming drawbacks on the conventional purification methods. This study aimed to purify bovine serum albumin (BSA) as an exemplary target product using an aqueous impregnated resin system (AIRS). This method implies the concept of hydrophobicity of polymer that impregnated into the resins and driven by electrostatic attractions and hydrophilicity of aqueous salt solution to extract the target product.

Methods

The extraction behaviors of impregnation in terms of stability and adsorption kinetics via protein-aqueous polymer impregnated resin were studied. Impregnation stability was determined by the leaching factor of polyethylene glycol (PEG). The major factors such as PEG molecular weights and concentration, pH of aqueous salt solution, extraction methods (sonication and agitation) and types of adsorbent material and concentration of aqueous salt phase influencing on partitioning of biomolecule were also investigated.

Results

For impregnation stability, the leaching factor for Amberlite XAD4 did not exceed 1%. The scanning electron microscopy (SEM) image analysis of Amberlite XAD4 attributes the structural changes with impregnation of resins. For adsorption kinetics, Freundlich adsorption isotherm with the highest R² value (0.95) gives an indication of favorable adsorption process. Performance of AIRS impregnated with 40% (w/w) of PEG 2000 was found better than aqueous-two phase system (ATPS) by yielding the highest recovery of BSA (53.72%). The outcomes of this study propound the scope for the application of AIRS in purification of biomolecules.

Advances Brought by Hydrophilic Ionic Liquids in Fields Involving Pharmaceuticals

The negligible volatility and high tunable nature of ionic liquids (ILs) have been the main drivers of their investigation in a wide diversity of fields, among which is their application in areas involving pharmaceuticals. Although most literature dealing with ILs is still majorly devoted to hydrophobic ILs, evidence on the potential of hydrophilic ILs have been increasingly provided in the past decade, viz., ILs with improved therapeutic efficiency and bioavailability, ILs with the ability to increase drugs' aqueous solubility, ILs with enhanced extraction performance for pharmaceuticals when employed in biphasic systems and other techniques, and ILs displaying low eco/cyto/toxicity and beneficial biological activities. Given their relevance, it is here overviewed the applications of hydrophilic ILs in fields involving pharmaceuticals, particularly focusing on achievements and advances witnessed during the last decade. The application of hydrophilic ILs within fields involving pharmaceuticals is here critically discussed according to four categories: (i) to improve pharmaceuticals solubility, envisioning improved bioavailability; (ii) as IL-based drug delivery systems; (iii) as pretreatment techniques to improve analytical methods performance dealing with pharmaceuticals, and (iv) in the recovery and purification of pharmaceuticals using IL-based systems. Key factors in the selection of appropriate ILs are identified. Insights and perspectives to bring renewed and effective solutions involving ILs able to compete with current commercial technologies are finally provided.

Phase separation property of a hydrophobic deep eutectic solvent-water binary mixture: A molecular dynamics simulation study

Over the past decade, deep eutectic solvents (DESs) have earned applicability in numerous fields as non-flammable, non-volatile, and greener alternatives to conventional organic solvents. In a first of its kind, a hydrophobic DES composed of a 1:1 mixture of oleic acid and lidocaine was recently reported, possessing a lower critical solution temperature in water. The thermoreversible phase property of this DES-water system was utilized to sequester out dye molecules from their aqueous solutions. In this article, we explore the phase separation phenomena for this particular DES in its aqueous solution using an all-atom molecular dynamics simulation. A 50 wt. % solution of the DES in water was studied at three different temperatures (253, 293, and 313 K) to understand the various molecular interactions that dictate the phase segregation property of these systems. In this work, we have elaborated on the importance of hydrogen bonding interactions and the non-bonding interactions between the components and the competition between the two that leads to phase separation. Overall, we observe that the increase in unfavorable interaction between the DES components and water with increasing temperature determines the phase separation behavior. We have also studied the modification in the dynamical properties of water molecules close to the phase boundary. Such molecular insights would be beneficial for designing novel solvent systems that can be used as extraction-based media in industries.

Unusual Application for Phosphonium Salts and Phosphoranes: Synthesis of Chalcogenides

A novel strategy for the synthesis of sulfides and selenides from phosphonium salts and thio- or selenesulfonates, commercially available compounds, is described. When phosphoranes were used in the reaction, different products were obtained. The methodology does not require the use of metals, reactive species, or anhydrous conditions to be performed.

Efficacy of alcohol/sugar aqueous biphasic system on partition of bovine serum albumin

The efficacy of alcohol/sugar aqueous biphasic (ABS) system on protein extraction was investigated. A model protein, bovine serum albumin (BSA), was adopted to evaluate the effects of types and concentration of phase-forming components, protein concentration, and system pH on the protein partition efficiency. The 1-propanol/maltose ABS exhibited an overall better partition efficiency of BSA to the alcohol-rich top phase. A maximum partition coefficient (K) of 20.01 ± 0.05 and recovery yield (Y) of 95.42% ± 0.01% of BSA were achieved with 35% (w/w) 1-propanol/22% (w/w) maltose ABS at pH 5.0 for 10% (w/w) BSA load. The K and Y of BSA in 1-propanol/maltose ABS was slightly improved with the addition of 3% (w/w) of ionic liquid, 1-butyl-3-methylimidazolium bromide ([Bmim]Br) as the adjuvant that could provide protein stabilizing effect. The Fourier Transform Infrared Spectrum (FTIR) analysis revealed that the protein structure remained unaltered upon the separation process.

Glycine-betaine ionic liquid analogues as novel phase-forming components of aqueous biphasic systems

Given the biotechnology advances observed in recent years in terms of upstream, the development of effective downstream processes becomes mandatory to decrease the associated costs of biotechnological-based products. Although a large interest has been devoted to ionic-liquid-based aqueous biphasic systems (IL-based ABS) as tailored separation platforms, imidazolium-based ILs have been the preferred choice as phase-forming agents. To overcome some toxicity and biodegradability issues associated to imidazolium-based ILs, novel ABS composed of ILs analogues of glycine-betaine (AGB-ILs) are here proposed and investigated. Five AGB-ILs were synthesized, characterized in terms of ecotoxicity, and applied toward the development of novel ABS formed with Na₂ SO₄ . Three commercial ILs were also investigated for comparison purposes. The respective ABS ternary phase diagrams, as well as the tie-lines and tie-line lengths, were determined at 25°C. Finally, their performance as extraction strategies was evaluated with five amino acids (L-tryptophan, L-phenylalanine, D-phenylalanine, L-tyrosine and L-3,4-dihydroxyphenylalanine/L-dopa). In all studied systems amino acids preferentially migrate to the IL-rich phase, and with AGB-ILs, the amino acid extraction efficiencies to the IL-rich phase range between 65% and 100%, obtained in a single-step. Furthermore, the studied AGB-ILs display a higher ability to form ABS and to extract amino acids than ABS composed of more traditional and commercial ILs. In summary, novel ABS composed of AGB-ILs can be formed and used as separation routes of value-added compounds of biotechnological interest. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 2018 © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 34:1205-1212, 2018.

Separation of immunoglobulin G using aqueous biphasic systems composed of cholinium-based ionic liquids and poly(propylene glycol)

BACKGROUND

The use of antibodies, such as immunoglobulin G (IgG), has faced a significant growth in the past decades for biomedical and research purposes. However, antibodies are high cost biopharmaceuticals, for which the development of alternative and cost-effective purification strategies is still in high demand.

RESULTS

Aqueous biphasic systems (ABS) composed of poly(propylene glycol) (PPG) and cholinium-based ionic liquids (ILs) were investigated for the separation of IgG. The ABS phase diagrams were determined and characterized whenever required. Initial optimization studies with commercial IgG were carried out, followed by the extraction of IgG from rabbit serum. In all ABS, IgG preferentially partitions to the IL-rich phase, unveiling preferential interactions between IgG and ILs. Good results were obtained with commercial IgG, with extraction efficiencies ranging between 93% and 100%, and recovery yields ranging between 20% and 100%. Two of the best and two of the worst identified ABS were then evaluated in what concerns their performance to separate and recover IgG from rabbit serum. With these ABS, extraction efficiencies of 100% and recovery yields > 80% were obtained, indicating an increase in the recovery yield and extraction efficiencies when using real matrices. Under the best conditions studied, IgG with a purity level of 49% was obtained in a single-step. This purity level of IgG is higher than those previously reported using other IL-polymer ABS.

CONCLUSION

IgG preferentially migrates to the IL-rich phase in ABS formed by ILs and polymers, allowing the design of effective separation systems for its recovery from serum samples.

Ionic liquids as biocompatible stabilizers of proteins

Ionic liquids (ILs) have recently emerged as versatile solvents and additives in the field of biotechnology, particularly as stabilizers of proteins and enzymes. Of interest to the biotechnology industry is the formulation of stable biopharmaceuticals, therapeutic proteins, and vaccines which have revolutionized the treatment of many diseases including debilitating conditions such as cancers and auto-immune diseases. The stabilization of therapeutic proteins is typically achieved using additives that prevent unfolding and aggregation of these proteins during manufacture, transport, and long-term storage. To determine if ILs could be used in the formulation of stable therapeutic proteins, a thorough understanding of the effects of ILs on protein stability is needed, as well as understanding the toxicity of ILs on humans, and other considerations for formulation development such as viscosity and osmolality. In this review, we summarize recent developments on the stabilization of proteins and enzymes using ILs, with emphasis on identifying biocompatible ILs that may be suitable for the formulation of stable biopharmaceuticals in the future.

Good's Buffer Ionic Liquids as Relevant Phase-Forming Components of Self-Buffered Aqueous Biphasic Systems

A series of new self-buffering ionic liquids (ILs) based on Good's buffers (GBs) anions and the tetrabutylphosphonium cation ([P₄₄₄₄]⁺) was here synthesized and characterized. The self-buffering behaviour of the GB-ILs was confirmed by measuring their protonation constants by potentiometry. Further, their ability to form aqueous biphasic systems with the biodegradable potassium citrate salt was evaluated, and further investigated for the extraction of proteins, using bovine serum albumin (BSA) as a model protein. If these ionic structures display self-buffering characteristics as well as a low toxicity towards the luminescent bacteria Vibrio fischeri, they were additionally found to be highly effective in the formation of ABS and in the extraction of BSA - extraction efficiencies of 100% to the IL-rich phase obtained in a single-step. The BSA secondary structure in the aqueous IL-rich solutions was evaluated through infrared spectroscopic studies revealing the protein-friendly nature of the synthesized ILs. Dynamic light scattering (DLS), "COnductor-like Screening MOdel for Real Solvents" (COSMO-RS), and molecular docking studies were finally carried out to better understand the main driving forces of the extraction process. The results suggest that van der Waals and hydrogen-bonding interactions are important driving forces of the protein migration towards the GB-IL-rich phase, while the molecular docking investigations demonstrated a stabilizing effect of the studied ILs over the protein.

Ionic-Liquid-Mediated Extraction and Separation Processes for Bioactive Compounds: Past, Present, and Future Trends

Ionic liquids (ILs) have been proposed as promising media for the extraction and separation of bioactive compounds from the most diverse origins. This critical review offers a compilation on the main results achieved by the use of ionic-liquid-based processes in the extraction and separation/purification of a large range of bioactive compounds (including small organic extractable compounds from biomass, lipids, and other hydrophobic compounds, proteins, amino acids, nucleic acids, and pharmaceuticals). ILs have been studied as solvents, cosolvents, cosurfactants, electrolytes, and adjuvants, as well as used in the creation of IL-supported materials for separation purposes. The IL-based processes hitherto reported, such as IL-based solid-liquid extractions, IL-based liquid-liquid extractions, IL-modified materials, and IL-based crystallization approaches, are here reviewed and compared in terms of extraction and separation performance. The key accomplishments and future challenges to the field are discussed, with particular emphasis on the major lacunas found within the IL community dedicated to separation processes and by suggesting some steps to overcome the current limitations.

Natural deep eutectic solvents: cytotoxic profile

The purpose of this study was to investigate the cytotoxic profiles of different ternary natural deep eutectic solvents (NADESs) containing water. For this purpose, five different NADESs were prepared using choline chloride as a salt, alongside five hydrogen bond donors (HBD) namely glucose, fructose, sucrose, glycerol, and malonic acid. Water was added as a tertiary component during the eutectics preparation, except for the malonic acid-based mixture. Coincidentally, the latter was found to be more toxic than any of the water-based NADESs. A trend was observed between the cellular requirements of cancer cells, the viscosity of the NADESs, and their cytotoxicity. This study also highlights the first time application of the conductor-like screening model for real solvent (COSMO-RS) software for the analysis of the cytotoxic mechanism of NADESs. COSMO-RS simulation of the interactions between NADESs and cellular membranes' phospholipids suggested that NADESs strongly interacted with cell surfaces and that their accumulation and aggregation possibly defined their cytotoxicity. This reinforced the idea that careful selection of NADESs components is necessary, as it becomes evident that organic acids as HBD highly contribute to the increasing toxicity of these neoteric mixtures. Nevertheless, NADESs in general seem to possess relatively less acute toxicity profiles than their DESs parents. This opens the door for future large scale utilization of these mixtures.

Recent advances in exploiting ionic liquids for biomolecules: Solubility, stability and applications

The technological utility of biomolecules (e.g. proteins, enzymes and DNA) can be significantly enhanced by combining them with ionic liquids (ILs) - potentially attractive "green" and "designer" solvents - rather than using in conventional organic solvents or water. In recent years, ILs have been used as solvents, cosolvents, and reagents for biocatalysis, biotransformation, protein preservation and stabilization, DNA solubilization and stabilization, and other biomolecule-based applications. Using ILs can dramatically enhance the structural and chemical stability of proteins, DNA, and enzymes. This article reviews the recent technological developments of ILs in protein-, enzyme-, and DNA-based applications. We discuss the different routes to increase biomolecule stability and activity in ILs, and the design of biomolecule-friendly ILs that can dissolve biomolecules with minimum alteration to their structure. This information will be helpful to design IL-based processes in biotechnology and the biological sciences that can serve as novel and selective processes for enzymatic reactions, protein and DNA stability, and other biomolecule-based applications.

Single-Step Purification of Ovalbumin from Egg White Using Aqueous Biphasic Systems

The ability of aqueous biphasic systems (ABS) composed of polyethylene glycols of different molecular weights (PEG 400, 600 and 1000) and buffered aqueous solutions of potassium citrate/citric acid (pH = 5.0 - 8.0) to selectively extract ovalbumin from egg white was here investigated. Phase diagrams, tie-lines and tie-line lengths were determined at 25ºC and the partitioning of ovalbumin in these systems was then evaluated. Aiming at optimizing the selective extraction of ovalbumin in the studied ABS, factors such as pH, PEG molecular weight and amount of the phase-forming components were initially investigated with pure commercial ovalbumin. In almost all ABS, it was observed a preferential partitioning of ovalbumin to the polymer-rich phase, with extraction efficiencies higher than 90%. The best ABS were then applied in the purification of ovalbumin from the real egg white matrix. In order to ascertain on the ovalbumin purity and yield, sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and size exclusion high performance liquid chromatography (SE-HPLC) analyses were conducted, confirming that the isolation/purification of ovalbumin from egg white was completely achieved in a single-step with a recovery yield of 65%. The results obtained show that polymer-salt-based ABS allow the selective extraction of ovalbumin from egg white with a simpler approach and better performance than previously reported. Finally, it is shown that ovalbumin can be completely recovered from the PEG-rich phase by an induced precipitation using an inexpensive and sustainable separation platform which can be easily applied on an industrial scale.

Lysozyme Solubility and Conformation in Neat Ionic Liquids and Their Mixtures with Water

The room temperature solubility of a number of model proteins is assessed for a diverse set of neat ionic liquids (ILs). For two soluble protein-IL pairs, lysozyme in [C2MIM][EtSO4] (1-ethyl-3-methylimidazolium ethylsulfate) and in [C2,4,4,4P][Et2PO4] (tributyl(ethyl)phosphonium diethylphosphate), protein solubility and structure at various temperatures are probed by dynamic light scattering (assessing dissolved molecular size), turbidimetry (reflecting degree of solubility), and Fourier transform infrared spectroscopy (uncovering helical secondary structure). As compared to aqueous environments, [C2,4,4,4P][Et2PO4] thermally stabilizes protein size and secondary structure while [C2MIM][EtSO4] does the opposite. Lysozyme denatured in [C2MIM][EtSO4] does not aggregate, presumably due to an absence of hydrophobic interactions, and the denaturation appears thermally reversible. Both ILs at room temperature are miscible with water in all proportions, but to create the corresponding ternary mixtures with protein, the order of mixing is important. Mixed to avoid additions of water to IL-dissolved protein, stable solutions are obtained with [C2MIM][EtSO4] at all solvent compositions. When water is added to IL-rich solutions, liquid-liquid demixing is noted.

Enhanced tunability afforded by aqueous biphasic systems formed by fluorinated ionic liquids and carbohydrates

This work unveils the formation of novel aqueous biphasic systems (ABS) formed by perfluoroalkylsulfonate-based ionic liquids (ILs) and a large number of carbohydrates (monosaccharides, disaccharides and polyols) aiming at establishing more benign alternatives to the salts commonly used. The respective ternary phase diagrams were determined at 298 K. The aptitude of the carbohydrates to induce phase separation closely follows their hydration capability, while the length of the IL cation/anion fluorinated chain also plays a crucial role. Finally, these systems were investigated as liquid-liquid extraction strategies for four food dyes. Single-step extraction efficiencies for the carbohydrate-rich phase up to 94% were obtained. Remarkably and contrarily to the most investigated IL-salt ABS, most dyes preferentially migrate for the most hydrophilic and biocompatible carbohydrate-rich phase - an outstanding advantage when envisaging the products recovery and further use. On the other hand, more hydrophobic dyes preferentially partition to the IL-rich phase, disclosing therefore these novel systems as highly amenable to be tuned by the proper choice of the phase-forming components.

Thermoreversible (Ionic-Liquid-Based) Aqueous Biphasic Systems

The ability to induce reversible phase transitions between homogeneous solutions and biphasic liquid-liquid systems, at pre-defined and suitable operating temperatures, is of crucial relevance in the design of separation processes. Ionic-liquid-based aqueous biphasic systems (IL-based ABS) have demonstrated superior performance as alternative extraction platforms, and their thermoreversible behaviour is here disclosed by the use of protic ILs. The applicability of the temperature-induced phase switching is further demonstrated with the complete extraction of two value-added proteins, achieved in a single-step. It is shown that these temperature-induced mono(bi)phasic systems are significantly more versatile than classical liquid-liquid systems which are constrained by their critical temperatures. IL-based ABS allow to work in a wide range of temperatures and compositions which can be tailored to fit the requirements of a given separation process.

Refolding effects of partially immiscible ammonium-based ionic liquids on the urea-induced unfolded lysozyme structure

Refolding ability of partially-immiscible ammonium-based ionic liquids on the urea-induced unfolded lysozyme.

PEGylated silica-enzyme nanoconjugates: a new frontier in large scale separation of α-amylase

High resolution is nearly lost at the expense of throughput in most conventional bioseparation methods. Nanoparticles, due to their high surface to volume ratio, are attractiveenzyme carriers, which can boost the performance of extraction manifold. Here, wereport design and application ofa method highly capable of improving the partitioning of α-amylase in aqueous two-phase system of polymer and salt. Silica nanoparticle introduced to the system acts as a bridge that connects the enzyme and polymer. Theconjugated nanoparticles form the major part of the upper phase and thus significantly enhance the protein recovery. A thorough investigation was performed on the structure of the nanoconjugatesas well as analyzing the conformational structure of the enzyme after conjugationto explore anypossible denaturation.