Aqueous two-phase affinity partitioning systems: Current applications and trends

Mechanisms ruling the partition of solutes in ionic-liquid-based aqueous biphasic systems - the multiple effects of ionic liquids

In the past decade, the remarkable potential of ionic-liquid-based aqueous biphasic systems (IL-based ABSs) to extract and purify a large range of valued-added biocompounds has been demonstrated. However, the translation of lab-scale experiments to an industrial scale has been precluded by a poor understanding of the molecular-level mechanisms ruling the separation or partition of target compounds between the coexisting phases. To overcome this limitation, we carried out a systematic evaluation of specific interactions, induced by ILs and several salts used as phase-forming components, and their impact on the partition of several solutes in IL-based ABSs. To this end, the physicochemical characterization of ABSs composed of imidazolium-based ILs, three salts (Na2SO4, K2CO3 and K3C6H5O7) and water was performed. The ability of the coexisting phases to participate in different solute-solvent interactions (where "solvent" corresponds to each ABS phase) was estimated based on the Gibbs free energy of transfer of a methylene group between the phases in equilibrium, ΔG(CH2), and on the Kamlet-Taft parameters - dipolarity/polarizability (π*), hydrogen-bonding donor acidity (α) and hydrogen-bonding acceptor basicity (β) - of the coexisting phases. Relationships between the partition coefficients, the phase properties expressed as Kamlet-Taft parameters and COSMO-RS descriptors were established, highlighting the ability of ILs to establish specific interactions with given solutes. The assembled results clearly support the idea that the partition of solutes in IL-based ABSs is due to multiple effects resulting from both global solute-solvent and specific solute-IL interactions. Solute-IL specific interactions are often dominant in IL-based ABSs, explaining the higher partition coefficients, extraction efficiencies and selectivities observed with these systems when compared to more traditional ones majorly composed of polymers.

A multiplexed microfluidic toolbox for the rapid optimization of affinity-driven partition in aqueous two phase systems

Antibodies and other protein products such as interferons and cytokines are biopharmaceuticals of critical importance which, in order to be safely administered, have to be thoroughly purified in a cost effective and efficient manner. The use of aqueous two-phase extraction (ATPE) is a viable option for this purification, but these systems are difficult to model and optimization procedures require lengthy and expensive screening processes. Here, a methodology for the rapid screening of antibody extraction conditions using a microfluidic channel-based toolbox is presented. A first microfluidic structure allows a simple negative-pressure driven rapid screening of up to 8 extraction conditions simultaneously, using less than 20μL of each phase-forming solution per experiment, while a second microfluidic structure allows the integration of multi-step extraction protocols based on the results obtained with the first device. In this paper, this microfluidic toolbox was used to demonstrate the potential of LYTAG fusion proteins used as affinity tags to optimize the partitioning of antibodies in ATPE processes, where a maximum partition coefficient (K) of 9.2 in a PEG 3350/phosphate system was obtained for the antibody extraction in the presence of the LYTAG-Z dual ligand. This represents an increase of approx. 3.7 fold when compared with the same conditions without the affinity molecule (K=2.5). Overall, this miniaturized and versatile approach allowed the rapid optimization of molecule partition followed by a proof-of-concept demonstration of an integrated back extraction procedure, both of which are critical procedures towards obtaining high purity biopharmaceuticals using ATPE.

From Current Algae Products to Future Biorefinery Practices: A Review

Microalgae are considered to be one of the most promising next generation bio-based/food feedstocks with a unique lipid composition, high protein content, and an almost unlimited amount of other bio-active molecules. High-value components such as the soluble proteins, (poly) unsaturated fatty acids, pigments, and carbohydrates can be used as an important ingredient for several markets, such as the food/feed/chemical/cosmetics and health industries. Although cultivation costs have decreased significantly in the last few decades, large microalgae production processes become economically viable if all complex compounds are optimally valorized in their functional state. To isolate these functional compounds from the biomass, cost-effective, mild, and energy-efficient biorefinery techniques need to be developed and applied. In this review we describe current microalgae biorefinery strategies and the derived products, followed by new technological developments and an outlook toward future products and the biorefinery philosophy.

Aqueous two-phase system (ATPS): an overview and advances in its applications

Aqueous two-phase system (ATPS) is a liquid-liquid fractionation technique and has gained an interest because of great potential for the extraction, separation, purification and enrichment of proteins, membranes, viruses, enzymes, nucleic acids and other biomolecules both in industry and academia. Although, the partition behavior involved in the method is complex and difficult to predict. Current research shows that it has also been successfully used in the detection of veterinary drug residues in food, separation of precious metals, sewage treatment and a variety of other purposes. The ATPS is able to give high recovery yield and is easily to scale up. It is also very economic and environment friendly method. The aim of this review is to overview the basics of ATPS, optimization and its applications.

Miniaturization of aqueous two-phase extraction for biological applications: From micro-tubes to microchannels

Aqueous two-phase extraction (ATPE) is a biocompatible liquid-liquid (L-L) separation technique that has been under research for several decades towards the purification of biomolecules, ranging from small metabolites to large animal cells. More recently, with the emergence of rapid-prototyping techniques for fabrication of microfluidic structures with intricate designs, ATPE gained an expanded range of applications utilizing physical phenomena occurring exclusively at the microscale. Today, research is being carried simultaneously in two different volume ranges, mL-scale (microtubes) and nL-scale (microchannels). The objective of this review is to give insight into the state of the art at both microtube and microchannel-scale and to analyze whether miniaturization is currently a competing or divergent technology in a field of applications including bioseparation, bioanalytics, enhanced fermentation processes, catalysis, high-throughput screening and physical/chemical compartmentalization. From our perspective, both approaches are worthy of investigation and, depending on the application, it is likely that either (i) one of the approaches will eventually become obsolete in particular research areas such as purification at the preparative scale or high-throughput screening applications; or (ii) both approaches will function as complementing techniques within the bioanalytics field.

Extraction and characterization of polysaccharides from Semen Cassiae by microwave-assisted aqueous two-phase extraction coupled with spectroscopy and HPLC

A novel and rapid method for simultaneous extraction and separation of the different polysaccharides from Semen Cassiae (SC) was developed by microwave-assisted aqueous two-phase extraction (MAATPE) in a one-step procedure. Using ethanol/ammonium sulfate system as a multiphase solvent, the effects of MAATPE on the extraction of polysaccharides from SC such as the composition of the ATPS, extraction time, temperature and solvent-to-material ratio were investigated by UV-vis analysis. Under the optimum conditions, the yields of polysaccharides were 4.49% for the top phase, 8.80% for the bottom phase and 13.29% for total polysaccharides, respectively. Compared with heating solvent extraction and ultrasonic assisted extraction, MAATPE exhibited the higher extraction yields in shorter time. Fourier-transform infrared spectra showed that two polysaccharides extracted from SC to the top and bottom phases by MAATPE were different from each other in their chemical structures. Through acid hydrolysis and PMP derivatization prior to HPLC, analytical results by indicated that a polysaccharide of the top phases was a relatively homogeneous homepolysaccharide composed of dominant gucose glucose while that of the bottom phase was a water-soluble heteropolysaccharide with multiple components of glucose, xylose, arabinose, galactose, mannose and glucuronic acid. Molar ratios of monosaccharides were 95.13:4.27:0.60 of glucose: arabinose: galactose for the polysaccharide from the top phase and 62.96:14.07:6.67: 6.67:5.19:4.44 of glucose: xylose: arabinose: galactose: mannose: glucuronic acid for that from the bottom phase, respectively. The mechanism for MAATPE process was also discussed in detail. MAATPE with the aid of microwave and the selectivity of the ATPS not only improved yields of the extraction, but also obtained a variety of polysaccharides. Hence, it was proved as a green, efficient and promising alternative to simultaneous extraction of polysaccharides from SC.

Partitioning in aqueous two-phase systems: Analysis of strengths, weaknesses, opportunities and threats

For half a century aqueous two-phase systems (ATPSs) have been applied for the extraction and purification of biomolecules. In spite of their simplicity, selectivity, and relatively low cost they have not been significantly employed for industrial scale bioprocessing. Recently their ability to be readily scaled and interface easily in single-use, flexible biomanufacturing has led to industrial re-evaluation of ATPSs. The purpose of this review is to perform a SWOT analysis that includes a discussion of: (i) strengths of ATPS partitioning as an effective and simple platform for biomolecule purification; (ii) weaknesses of ATPS partitioning in regard to intrinsic problems and possible solutions; (iii) opportunities related to biotechnological challenges that ATPS partitioning may solve; and (iv) threats related to alternative techniques that may compete with ATPS in performance, economic benefits, scale up and reliability. This approach provides insight into the current status of ATPS as a bioprocessing technique and it can be concluded that most of the perceived weakness towards industrial implementation have now been largely overcome, thus paving the way for opportunities in fermentation feed clarification, integration in multi-stage operations and in single-step purification processes.

Determination of sunset yellow and tartrazine in food samples by combining ionic liquid-based aqueous two-phase system with high performance liquid chromatography

We proposed a simple and effective method, by coupling ionic liquid-based aqueous two-phase systems (IL-ATPSs) with high performance liquid chromatography (HPLC), for the analysis of determining tartrazine and sunset yellow in food samples. Under the optimized conditions, IL-ATPSs generated an extraction efficiency of 99% for both analytes, which could then be directly analyzed by HPLC without further treatment. Calibration plots were linear in the range of 0.01-50.0 μg/mL for both Ta and SY. The limits of detection were 5.2 ng/mL for Ta and 6.9 ng/mL for SY. This method proves successful for the separation/analysis of tartrazine and sunset yellow in soft drink sample, candy sample, and instant powder drink and leads to consistent results as obtained from the Chinese national standard method.

Extraction and separation of proteins by ionic liquid aqueous two-phase system

A satisfactory protocol of protein extraction and separation has been established based on the ionic liquid aqueous two-phase system (IL-ATPS) for the purification of bioactive substances. Compared with the effects of eight different ionic liquids, 1-octyl-3-methylimidazolium bromide ([omim][Br]) was selected as the suitable ionic liquid. Based on the single-factor experiment, an initial serial investigative test was used to identify the optimal conditions of the extraction. Owing to their different isoelectric points, bovine serum albumin (BSA), hemoglobin (Hb) and lysozyme (Lys) were used to determine the effect of pH value on the protein extraction. Trypsin (Try) was used to confirm the protein activity. The linearity for analyzing BSA, Hb, Try and Lys was in the concentration range of 0.05-1.00 mg ml(-1), 0.025-1 mg ml(-1), 0.01-1.00 mg ml(-1) and 0.01-1.00 mg ml(-1), respectively, with a correlation coefficient of between 0.9985 and 0.9999. Limits of detection (LODs) were 16.47-7.02 μg ml(-1) and RSDs of inter-day stability were less than 2.9%. Repeatability and precision were respectively lower than 5.3% and 1.1%. Under the optimum conditions, the average recoveries of BSA, Hb, Try and Lys were 90.5%, 94.5%, 92.7% and 93.8% and the obtained RSDs were 1.19%, 1.23%, 1.34% and 1.04%, respectively. According to UV spectra, conductivity, dynamic light scattering (DLS), and transmission electron microscope (TEM) images, the cluster phenomenon originating from IL itself or combined with protein was evaluated. As the driving forces which are involved in the partitioning of protein between the IL-rich phase and the phosphate phase, the cluster phenomenon could, in principle, be applied to a variety of different samples and exhibited potential value.

Phase separation as a possible means of nuclear compartmentalization

The nucleus is perhaps the most familiar organelle within eukaryotic cells, serving as a compartment to house the genetic material. The nuclear volume is subdivided into a variety of functional and dynamic nuclear bodies not separated from the nucleoplasm by membranes. It has been hypothesized that aqueous phase separation brought about by macromolecular crowding may be in part responsible for these intranuclear compartments. This chapter discusses macromolecular solution chemistry with regard to several common types of phase separation in polymer solutions as well as to recent evidence that suggests that cytoplasmic and nuclear bodies may exist as liquid phases. We then examine the functional significance of phase separation and how it may serve as a means of compartmentalizing various nuclear activities, and describe recent studies that have used simple model systems to generate coexisting aqueous phase compartments, concentrate molecules within them, and perform localized biochemical reactions.