Surfactant as selective modulator in the partitioning of dyes in aqueous two-phase systems: A strategy for separation

Improvement effect of p-sulfonatocalix[4]arene on the performance of the PEG/salt aqueous two-phase system

The PEG/salt aqueous two-phase system (ATPS) is the most common ATPS, but its application is still limited due to the restricted polarity difference between the two phases and the poor enhancement effect of adjuvants on ATPS performance so far. Unlike the adjuvants used so far, calixarenes can bind ions and molecules via multiple noncovalent interactions. In the present study, a water-soluble calixarene, p-sulfonatocalix[4]arene (SC[4]), was used for the first time as the adjuvant to improve the performance of the PEG 600/(NH₄)₂SO₄ ATPS through multiple interactions. It is found that when the SC[4] and the SC[4]/imidazole ionic liquid ([C_nmim]Br) complex were used as the adjuvants, the formation of PEG 600/(NH₄)₂SO₄ ATPS was enhanced, and the transfer of the extracts (including S-mandelic acid, L-tryptophan, and L-phenylalanine) into the PEG phase was promoted. Moreover, although the single [C_nmim]Br, a commonly used adjuvant, does not promote the migration of the target molecules into the polymer phase, the SC[4]/[C_nmim]Br complex is superior to SC[4] in enhancing the performance of the ATPS because the SC[4]/[C_nmim]Br aggregates enable more binding sites to combine with the extract. Besides, the partition coefficient of SC[4] in the PEG/trisodium citrate ATPS is much smaller than that in the PEG/(NH₄)₂SO₄ ATPS, which is helpful for the recovery of extracts into the citrate phase.

Recent progress in the synthesis of all-aqueous two-phase droplets using microfluidic approaches

An aqueous two-phase system (ATPS) is a system with liquid-liquid phase separation and shows great potential for the extraction, separation, purification, and enrichment of proteins, membranes, viruses, enzymes, nucleic acids, and other biomolecules because of its simplicity, biocompatibility, and wide applicability [1-4]. The clear aqueous-aqueous interface of ATPSs is highly advantageous for their implementation, therefore making ATPSs a green alternative approach to replace conventional emulsion systems, such as water-in-oil droplets. All aqueous emulsions (water-in-water, w-in-w) hold great promise in the biomedical field as glucose sensors [5] and promising carriers for the encapsulation and release of various biomolecules and nonbiomolecules [6-10]. However, the ultralow interfacial tension between the two phases is a hurdle in generating w-in-w emulsion droplets. In the past, bulk emulsification and electrospray techniques were employed for the generation of w-in-w emulsion droplets and the fabrication of microparticles and microcapsules in the later stage. Bulk emulsification is a simple and low-cost technique; however, it generates polydisperse w-in-w emulsion droplets. Another technique, electrospray, involves easy experimental setups that can generate monodisperse but nonspherical w-in-w emulsion droplets. In comparison, microfluidic platforms provide monodisperse w-in-w emulsion droplets with spherical shapes, deal with the small volumes of solutions and short reaction times and achieve portability and versatility in their design through rapid prototyping. Owing to several advantages, microfluidic approaches have recently been introduced. To date, several different strategies have been explored to generate w-in-w emulsions and multiple w-in-w emulsions and to fabricate microparticles and microcapsules using conventional microfluidic devices. Although a few review articles on ATPSs emulsions have been published in the past, to date, few reviews have exclusively focused on the evolution of microfluidic-based ATPS droplets. The present review begins with a brief discussion of the history of ATPSs and their fundamentals, which is followed by an account chronicling the integration of microfluidic devices with ATPSs to generate w-in-w emulsion droplets. Furthermore, the stabilization strategies of w-in-w emulsion droplets and microfluidic fabrication of microparticles and microcapsules for modern applications, such as biomolecule encapsulation and spheroid construction, are discussed in detail in this review. We believe that the present review will provide useful information to not only new entrants in the microfluidic community wanting to appreciate the findings of the field but also existing researchers wanting to keep themselves updated on progress in the field.

Recovery of value-added products from wastewater using Aqueous Two-Phase Systems - A review

Aqueous two-phase system (ATPS) is long seen as a technique that promotes higher purity and yield in a single step. It is witnessing increased acceptance as a preferred choice for combined goals of concentration, separation and purification of a target product, be it industrially valuable or environmentally contaminating. Purification of biomolecules like enzymes, proteins, nucleic acids, viruses, etc. has been the forte of ATPS. Currently, the technique is used for concentrating the toxic fractions from diverse industrial let offs, from food, dairy, beverage, pharmaceuticals, agriculture, dyeing, tannery and metal-processing industries. Apart from being simple, efficient, rapid, flexible, economical, and biocompatible, the selectivity, purity and yield are on par and sometimes higher than the traditional downstream steps. From an industrial angle too, problems related to scale-up of ATPS are being actively addressed. Many novel approaches are being added by way of varying ATPS components to increase the yield and purity. Another case in point is the inclusion of optimization techniques for zeroing in on the precise setting of the operating parameters. With increasing impetus to the approach, we attempt to draw attention from academia and industries, alike, that are developing novel tweaks to the currently existing practices in ATPS. This review aims to assess and evaluate the different types of ATPS that have been used for the recovery of valuables and contaminants from industrial waste discharges.

One-step procedure for peroxidase concentration, dye separation, and color removal by aqueous two-phase system

The aim of our study is to develop a one-step procedure to remove and degrade dyes from wastewater using a low-cost and efficient system based on aqueous two-phase system (ATPS), a well-known technique used to concentrate and recover enzymes. We investigated the catalytic proprieties of rice bran peroxidase (RBP) and found that this homemade enzyme can remain bound to its substrate for up to 5 days in controlled environments, without denaturing and while maintaining stable oxidation reduction potential (ORP) and pH. This biomolecule showed affinity for the ATPS technique prepared with polyethylene glycol and salt, which improved the relative activity up to 170%. The red dye separation in ATPS top phase was achieved in 3 min, in the RBP presence, with 100% of efficiency, and color removal of 87% was obtained in 24 h of enzymatic reaction. The process has promise to be scaled up to 10-fold and to reuse the reagents from the bottom phase of the ATPS.