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

3-Methyl Thiophene-Modified Boron-Doped Diamond (BDD) Electrodes as Efficient Catalysts for Phenol Detection-A Case Study for the Detection of Gallic Acid in Three Specific Tea Types

Polymer modification has been established as a cost-effective, simple, in situ method for overcoming some of the inherent disadvantages of boron-doped diamond (BDD) electrodes, and its application has been extended to reliable, low-cost environmental monitoring solutions. The present review focuses on modifying BDD electrodes with semi-conductive polymers acting as redox mediators. This article reports on the development of a 3-methyl thiophene-modified boron-doped diamond (BDD/P3MT) sensor for the electrochemical determination of total phenolic compounds (TPCs) in tea samples, using gallic acid (GA) as a marker. GA is a significant polyphenol with various biological activities, making its quantification crucial. Thus, a simple, fast, and sensitive GA sensor was fabricated using the electroanalytical square wave voltammetry (SWV) technique. The sensor utilizes a semi-conductive polymer, 3-methyl thiophene, as a redox mediator to enhance BDD's sensitivity and selectivity. Electrochemical synthesis was used for polymer deposition, allowing for greater purity and avoiding solubility problems. The BDD/P3MT sensor exhibits good electrochemical properties, including rapid charge transfer and a large electrochemical area, enabling GA detection with a limit of detection of 11 mg/L. The sensor's response was correlated with TPCs measured by the Folin-Ciocalteu method. Square wave voltammetry (SWV) showed a good linear relationship between peak currents and GA concentrations in a wide linear range of 3-71 mg/L under optimal conditions. The BDD/P3MT sensor accurately measured TPCs in green tea, rooibos tea, and black tea samples, with green tea exhibiting the highest TPC levels. The results demonstrate the potential of the modified BDD electrode for the rapid and accurate detection of phenolic compounds in tea, with implications for quality control and antioxidant activity assessments. The prolific publications of the past decade have established BDD electrodes as robust BDD sensors for quantifying polyphenols. Fruits, vegetables, nuts, plant-derived beverages such as tea and wine, traditional Eastern remedies and various herbal nutritional supplements contain phenolic chemicals. The safety concerns of contaminated food intake are significant health concerns worldwide, as there exists a critical nexus between food safety, nutrition, and food security. It has been well established that green tea polyphenol consumption promotes positive health effects. Despite their potential benefits, consuming high amounts of these polyphenols has sparked debate due to concerns over potential negative consequences.

Recent advances in drug delivery applications of aqueous two-phase systems

Aqueous two-phase systems (ATPSs) are liquid-liquid equilibria between two aqueous phases that usually contain over 70% water content each, which results in a nontoxic organic solvent-free environment for biological compounds and biomolecules. ATPSs have attracted significant interest in applications for formulating carriers (microparticles, nanoparticles, hydrogels, and polymersomes) which can be prepared using the spontaneous phase separation of ATPSs as a driving force, and loaded with a wide range of bioactive materials, including small molecule drugs, proteins, and cells, for delivery applications. This review provides a detailed analysis of various ATPSs, including strategies employed for particle formation, polymerization of droplets in ATPSs, phase-guided block copolymer assemblies, and stimulus-responsive carriers. Processes for loading various bioactive payloads are discussed, and applications of these systems for drug delivery are summarized and discussed.

What Can Be Learned from the Partitioning Behavior of Proteins in Aqueous Two-Phase Systems?

This review covers the analytical applications of protein partitioning in aqueous two-phase systems (ATPSs). We review the advancements in the analytical application of protein partitioning in ATPSs that have been achieved over the last two decades. Multiple examples of different applications, such as the quality control of recombinant proteins, analysis of protein misfolding, characterization of structural changes as small as a single-point mutation, conformational changes upon binding of different ligands, detection of protein-protein interactions, and analysis of structurally different isoforms of a protein are presented. The new approach to discovering new drugs for a known target (e.g., a receptor) is described when one or more previous drugs are already available with well-characterized biological efficacy profiles.

Extraction of collagenolytic proteases from Aspergillus heteromorphus URM 0269 in an aqueous two-phase system for application in collagen hydrolysis

Collagenolytic proteases produced by Aspergillus heteromorphus URM0269 were extracted using a PEG/sulfate aqueous two-phase system (ATPS). A 23 factorial design was performed to analyze the independent variables: PEG molar mass (MPEG), PEG concentration (CPEG), and sulfate concentration (Csulf). The extracted proteases were also evaluated for their optimum pH and stability at different pH levels (4.0 - 11.0) after 20 h of incubation. Collagen was extracted from mutton snapper (Lutjanus analis) skin using acetic acid (0.5 mol L-1). The enzyme was preferentially partitioned to the PEG-rich phase (K > 1), whose highest purification factor and recovery (PF = 6.256 and Y = 404.432%) were obtained under specific conditions: MPEG 8000 g.mol-1, CPEG 30%, Csulf 10%. The ATPS extraction provided an enzymatic activity range of pH 7.0 - 11.0, exhibiting greater stability compared to the crude extract. Approximately 80% of protease activity was maintained after 20 hours of incubation at all analyzed pH levels, except pH 11.0. Collagen extraction from L. analis skin yielded 8.056%, and both crude extract samples and ATPS-derived samples successfully hydrolyzed the extracted collagen, reaching peak hydrolysis after 36 hours of treatment. These findings demonstrate the feasibility of extracting highly purified and active proteases capable of hydrolyzing L. analis collagen.

Thermosensitive polymer-assisted extraction and purification of fungal laccase from citrus pulp wash effluent

BACKGROUND

This study explores the use of liquid-liquid extraction with thermosensitive polymers for producing laccase (Lac) from Pleurotus sajor-caju. This process leverages liquid waste from the citrus industry, specifically pulp wash. The research delves into extractive fermentation and thermoseparation, both processes being facilitated by a polymer exhibiting a lower critical solution temperature transition.

RESULTS

Key factors considered include the choice of polymer, its concentration, pH, separation temperature, and the behavior of the polymer-rich phase post-extractive fermentation concerning the lower critical solution temperature. Notably, under conditions of 45% by weight of Pluronic L-61 and pH 5.0 at 25 °C, the Lac resulted in an enhancement in the purification factor of 28.4-fold, compared with the Lac obtained directly from the fermentation process on the eighth day. There was an 83.6% recovery of the Lac enzyme in the bottom phase of the system. Additionally, the unique properties of Pluronic L-61, which can induce phase separation and also allow for thermoseparation, led to a secondary fraction (aqueous solution) of Lac with purification factor of 2.1 ± 0.1-fold (at 32 ± 0.9 °C and 30 ± 0.3 min without stirring) from the polymeric phase (top phase). Fourier-transform infrared analysis validated the separation data, particularly highlighting the α-helix content in the amide I region (1600-1700 cm-1 ).

CONCLUSION

In summary, the insights from this study pave the way for broader industrial applications of these techniques, underscoring benefits like streamlined process integration, heightened selectivity, and superior separation efficacy. © 2023 Society of Chemical Industry.

Selectivity of PEG/Salt Aqueous Two-Phase System Enhanced by Surfactant@MWCNT Composites

Aqueous two-phase systems (ATPS) are considered a new type of green separation system, but their low selectivity to target molecules limits their practical application. In this study, we used surfactant@MWCNT as an adjuvant to improve the selectivity of PEG/(NH4)2SO4 ATPS. The surfactants used include Triton X-100 (TX-100), Tween 80, sodium dodecyl sulfate (SDS), sodium dodecyl benzenesulfonate (SDBS), and bis(2-ethylhexyl)sulfosuccinate sodium salt (AOT). Nine aromatic compounds, including syringic acid, vanillin, tryptophan, phenylalanine, tyrosine, mandelic acid, theophylline, theobromine, and cephalexin, were selected as model extracts. The results showed that the use of the surfactant@MWCNT composite as an adjuvant significantly improved the selectivity of the ATPS toward syringic acid among the nine extracts. Moreover, the selectivity of the ATPS for syringic acid with the TX-100/MWCNT composite as the adjuvant is better than that with the Tween 80/MWCNT composite as the adjuvant, followed by that with the anionic surfactant/MWCNT composite as the adjuvant. The enhanced selectivity of ATPS by the surfactant/MWCNT composite is ascribed to the spatial effect and the electrostatic and hydrophobic interactions between the extract and the surfactant adsorbed on the MWCNT.

Sustainable Isolation of Bioactive Compounds and Proteins from Plant-Based Food (and Byproducts)

Plant-based food produces significantly less greenhouse gases, and due to its wealth of bioactive components and/or plant-based protein, it becomes an alternative in a sustainable food system. However, the processing and production of products from plant sources creates byproducts, which can be waste or a source of useful substances that can be reused. The waste produced during the production and processing of food is essentially nutrient- and energy-rich, and it is recognized as an excellent source of secondary raw materials that could be repurposed in the process of manufacturing and preparing food, or as feed for livestock. This review offers an overview of the sources and techniques of the sustainable isolation of bioactive substances and proteins from various sources that might represent waste in the preparation or production of food of plant origin. The aim is to uncover novel approaches to use waste and byproducts from the process of making food to provide this waste food an additional benefit, not forgetting the expectations of the end user, the consumer. For the successful isolation of bioactive ingredients and proteins from food of plant origin, it is crucial to develop more eco-friendly and efficient extraction techniques with a low CO2 footprint while considering the economic aspects.

Current status and future challenges in extraction, purification and identification of Cepharanthine (a potential drug against COVID-19)

With the outbreak of the new coronavirus disease 2019 (COVID-19), the rapid spread of the virus has brought huge economic losses and life threats to the world. So far, we have entered the third year of the epidemic and there is an urgent need to provide more anti-viral treatment along with vaccination. Recent studies have confirmed that Cepharanthine (CEP) has strong antiviral efficacy, which is a potential drug against COVID-19. As a natural active alkaloid, the development of CEP-incorporated products is dependent on the extraction, purification and identification of CEP. This review gives a brief introduction of CEP, including its origin and classification, and its conventional and novel extraction techniques. In addition, the purification and identification techniques are summarized. In the last, the future research directions are proposed. It can be found from this review that the extraction from plants is still the main way to obtain CEP, and it is necessary to use innovative techniques and their hybrid extractions to extract CEP. More efficient extraction and purification techniques should be used to extract CEP in the future. This review provides a basis for the development of novel extraction and purification techniques and industrial utilization of CEP.

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.

Thermoresponsive MXene composite system with high adsorption capacity for quick and simple removal of toxic metal ions from aqueous environment

High-performance adsorption and easy-to-recycle property of adsorbents are desirable in wastewater treatment, and a suitably smart adsorbent with responsive phase separation capacity is promising in this regard. Herein, a thermoresponsive composite system is designed through the combination of transition metal carbides (MXene) and poly(N-isopropylacrylamide) (PNIPAM) for removal of toxic metal ions from water. As a thermoresponsive switch, the PNIPAM endows such composite system with superior thermoresponsiveness (i.e., gel-water phase separation) in water, which facilitates to the control of adsorption. The gel phase triggered by an elevated temperature (e.g., 40 °C) quickly adsorbs toxic metal ions, and then a solid-liquid extraction way is used to conveniently separated the gel phase from water phase for simple removal of toxic metal ions. A very high adsorption capacity (e.g., ~224 mg·g^-1 for Cu²⁺) can be achieved due to the synergistic effects of the composite system. Moreover, the separated gel can be back to a redispersed state at low temperature (e.g., 20 °C), enabling its effective regeneration and recovery. Notably, the PNIPAM as a protective agent prevents the oxidation of MXene so as to retain good stability during the multiple adsorption/desorption cycles. This simple and smart adsorption strategy is great promising for water purification application.

An efficiency strategy for cobalt recovery from simulated wastewater by biphasic system with polyethylene glycol and ammonium sulfate

Today, biphasic aqueous systems have received more attention than conventional separation methods due to their advantages, such as biocompatibility, low cost, and easy operation. The extraction of cobalt ions from the aqueous phase with the absence and the presence of other ions was investigated using polyethylene glycol, and ammonium sulfate salt without using an extractant. The efficiency was evaluated using operating parameters such as aqueous pH, salt and polymer concentrations, phase volume ratio, and initial metal concentration. The higher temperature, and the lower aqueous pH showed a maximum transfer rate for cobalt ions into the PEG1000 phase. Extraction efficiency under optimal conditions equal to 50% (w/w) polyethylene glycol 1000, 4 M ammonium sulfate, aqueous pH = 2, and 15 min extraction time was over 98%. Results from infrared spectroscopy, and thermo-gravimetric analysis illustrated the presence of the PEG-cobalt ion complex. The observation demonstrated that the biphasic system is the proper technology for wastewater purification.

Remediation of diesel-contaminated soil by alkoxyethanol aqueous two-phase system

The increasing diesel pollution accidents pose a serious threat to the ecological environment and human health. Remediation of diesel-contaminated soil (DCS) has attracted widespread attention during the past few decades. This work proposed an approach for the remediation of DCS by alkoxyethanol aqueous two-phase extraction (ATPE), which was an application of this small molecule aqueous two-phase system (ATPS). In addition, the influence of temperature, stirring speed, stirring time, and solid-liquid ratio on the removal of diesel was explored respectively. The removal efficiency of diesel could reach more than 97.18% in 18 min. Meanwhile, ATPS had high reusability, and the removal efficiency remained above 85.17% in the reuse process. Alkoxyethanol ATPE could effectively remove diesel hydrocarbons with different carbon chain lengths and the remediation process hardly caused residual organic solvents on the soil surface according to the analysis of gas chromatography-mass spectrometry (GC-MS) and Fourier transforms infrared (FT-IR), which could be regarded as the distinct advantage compared to the traditional surfactant washing method and organic solvent extraction method. The study of soil physicochemical properties and wheat germination proved that the soil structure and properties changed little after ATPE remediation. And finally, the mechanism of alkoxyethanol ATPE was intensively discussed according to the remediation characteristic. This work provided an efficient method for the remediation of DCS and widened the application fields of alkoxyethanol ATPS as well.

Advances in downstream processes and applications of biological carboxylic acids derived from organic wastes

Recovering carboxylic acids derived from organic wastes from fermentation broth is challenging. To provide a reference for future study and industrial application, this review summarized recent advances in recovery technologies of carboxylic acids including precipitation, extraction, adsorption, membrane-based processes, etc. Meanwhile, applications of recovered carboxylic acids are summarized as well to help choose suitable downstream processes according to purity requirement. Integrated processes are required to remove the impurities from the complicated fermentation broth, at the cost of loss and expense. Compared with chemical processes, biological synthesis is better options due to low requirements for the substrates. Generally, the use of toxic agents, consumption of acid/alkaline and membrane fouling hamper the sustainability and scale-up of the downstream processes. Future research on novel solvents and materials will facilitate the sustainable recovery and reduce the cost of the downstream processes.

Pilot scale production, extraction and purification of a thermostable phycocyanin from Synechocystis sp. PCC 6803

Phycocyanin (PC) is a soluble blue pigment-protein primarily harvested from the cyanobacterium Arthrospira platensis. PC is in high demand from several industries, but its narrow stability range limits potential applications. Here, a pilot scale (120 L total) batch production, extraction and purification process for thermostable PC (Te-PC) from a Synechocystis sp. PCC 6803 'Olive' strain expressing the PC operon cpcBACD from Thermosynechococcus elongatus BP-1 on a self-replicating vector is presented. Batch cultivation without antibiotics had no impact on growth or Te-PC production and optimisation of growth conditions resulted in Te-PC contents of 75.3 ± 1.7 mg g DW^-1. Wet biomass was harvested following chitosan-based flocculation with a 97 ± 2% efficiency, and Te-PC was extracted by high pressure homogenisation. Subsequent purification by heat-treatment and two-step ammonium sulfate precipitation removed chlorophyll and allophycocyanin contamination, resulting in Te-PC purities of 2.9 ± 0.7 and a mean Te-PC recovery of 84 ± 12%.

Development of aqueous two-phase systems-based approaches for the selective recovery of metalloproteases and phospholipases A2 toxins from Crotalus molossus nigrescens venom

Snake venoms are rich sources of proteins with potential biotechnological and pharmaceutical applications. Among them, metalloproteases (MPs) and phospholipases A2 (PLA2) are the most abundant. Their isolation involves a multistep chromatographic approach, which has proven to be effective, however implies high operating costs and long processing times. In this study, a cost-effective and simple method based on aqueous two-phase systems (ATPS) was developed to recover MPs and PLA2 from Crotalus molossus nigrescens venom. A system with PEG 400 g mol-1, volume ratio (VR) 1, tie line length (TLL) 25% w/w and pH 7 showed the best performance for PLA2 recovery. In systems with PEG 400 g mol-1, VR 1, TLL 15% w/w, pH 7 and 1 and 3% w/w of NaCl, selective recovery of MP subtype P-III was achieved; whereas, in a system with PEG 400 g mol-1, VR 1, TLL 25% w/w and pH 8.5, MP subtypes P-I and P-III were recovered. Due to their low costs, ethanol-salt systems were also evaluated, however, failed to differentially partition PLA2 and MPs. The use of ATPS could contribute to the simplification and cost reduction of protein isolation processes from snake venoms and other toxin fluids, as well as potentially aid their biochemical, proteomic and biological analyses.

Initial Screening of Poly(ethylene glycol) Amino Ligands for Affinity Purification of Plasmid DNA in Aqueous Two-Phase Systems

Gene therapy and DNA vaccination are among the most expected biotechnological and medical advances for the coming years. However, the lack of cost-effective large-scale production and purification of pharmaceutical-grade plasmid DNA (pDNA) still hampers their wide application. Downstream processing, which is mainly chromatography-based, of pDNA remains the key manufacturing step. Despite its high resolution, the scaling-up of chromatography is usually difficult and presents low capacity, resulting in low yields. Alternative methods that are based on aqueous two-phase systems (ATPSs) have been studied. Although higher yields may be obtained, its selectivity is often low. In this work, modified polymers based on poly(ethylene glycol) (PEG) derivatisation with amino groups (PEG–amine) or conjugation with positively charged amino acids (PEG–lysine, PEG–arginine, and PEG–histidine) were studied to increase the selectivity of PEG–dextran systems towards the partition of a model plasmid. A two-step strategy was employed to obtain suitable pure formulations of pDNA. In the first step, a PEG–dextran system with the addition of the affinity ligand was used with the recovery of the pDNA in the PEG-rich phase. Then, the pDNA was re-extracted to an ammonium-sulphate-rich phase in the second step. After removing the salt, this method yielded a purified preparation of pDNA without RNA and protein contamination.

A Review on the Extraction and Processing of Natural Source-Derived Proteins through Eco-Innovative Approaches

In addition to their nutritional and physiological role, proteins are recognized as the major compounds responsible for the rheological properties of food products and their stability during manufacture and storage. Furthermore, proteins have been shown to be source of bioactive peptides able to exert beneficial effects on human health. In recent years, scholarly interest has focused on the incorporation of high-quality proteins into the diet. This fact, together with the new trends of consumers directed to avoid the intake of animal proteins, has boosted the search for novel and sustainable protein sources and the development of suitable, cost-affordable, and environmentally friendly technologies to extract high concentrations of valuable proteins incorporated into food products and supplements. In this review, current data on emergent and promising methodologies applied for the extraction of proteins from natural sources are summarized. Moreover, the advantages and disadvantages of these novel methods, compared with conventional methods, are detailed. Additionally, this work describes the combination of these technologies with the enzymatic hydrolysis of extracted proteins as a powerful strategy for releasing bioactive peptides.

An aqueous two-phase system formed in single-component solution of α-ketooctanoic acid

An aqueous two-phase system can form in the single-component solution of α-ketooctanoic acid without any additives.