Partitioning and purification of lysozyme from chicken egg white using aqueous two-phase system

Improved accuracy in pentraxin-3 quantification assisted by aqueous biphasic systems as serum pretreatment strategies

Although pentraxin-3 holds promise as a diagnosis/prognosis biomarker of microbial infections and lung cancer, its analysis in human serum can be constrained by matrix effects caused by high abundance proteins - human serum albumin and immunoglobulin G. Aqueous biphasic systems composed of polymers and citrate buffer are here proposed as a serum pretreatment step to improve the accuracy of pentraxin-3 analysis. Binodal curves were determined to identify the compositions required to form two phases and to correlate the polymers' properties and performance in serum pretreatment and biomarker extraction. Aqueous biphasic systems were evaluated regarding their ability to deplete human serum albumin and immunoglobulin G at the interphase. Polymers of relatively high to intermediate hydrophobicity were unveiled as efficient components to deplete high abundance serum proteins. Considering the possibility to extract pentraxin-3 from human serum into the polymer-rich phase, the system composed of polyethylene glycol with a molecular weight of 1000 g·mol-1 simultaneously achieved >93 % of human serum albumin and immunoglobulin G depletion and complete biomarker extraction. The accuracy of analysis of pretreated human serum by enzyme-linked immunosorbent assays outperformed that of a non-pretreated sample, with a relative error of 0.8 % compared to 14.6 %, contributing to boost pentraxin-3 usefulness as a biomarker.

Progress in all-aqueous droplets generation with microfluidics: Mechanisms of formation and stability improvements

All-aqueous systems have attracted intensive attention as a promising platform for applications in cell separation, protein partitioning, and DNA extraction, due to their selective separation capability, rapid mass transfer, and good biocompatibility. Reliable generation of all-aqueous droplets with accurate control over their size and size distribution is vital to meet the increasingly growing demands in emulsion-based applications. However, the ultra-low interfacial tension and large effective interfacial thickness of the water-water interface pose challenges for the generation and stabilization of uniform all-aqueous droplets, respectively. Microfluidics technology has emerged as a versatile platform for the precision generation of all-aqueous droplets with improved stability. This review aims to systematize the controllable generation of all-aqueous droplets and summarize various strategies to improve their stability with microfluidics. We first provide a comprehensive review on the recent progress of all-aqueous droplets generation with microfluidics by detailing the properties of all-aqueous systems, mechanisms of droplet formation, active and passive methods for droplet generation, and the property of droplets. We then review the various strategies used to improve the stability of all-aqueous droplets and discuss the fabrication of biomaterials using all-aqueous droplets as liquid templates. We envision that this review will benefit the future development of all-aqueous droplet generation and its applications in developing biomaterials, which will be useful for researchers working in the field of all-aqueous systems and those who are new and interested in the field.

Efficient Purification of Nuclease P1 from Penicillium citrinum Using Polyethylene Glycol/Disodium Guanosine Monophosphate Aqueous Two-Phase System

Nuclease P1 (NP1) can hydrolyze nucleic acids into four 5'-mononucleotides, which are widely used in the pharmaceutical and food industries. In this paper, an aqueous two-phase system (ATPS) was developed to purify NP1 from Penicillium citrinum. Polyethylene glycol (PEG) and nucleotides salts were studied to form ATPSs, among which PEG3000/disodium guanosine monophosphate (GMPNa₂) was researched, including the phase composition and pH. Using 14% (w/w) PEG3000 and 20% (w/w) GMPNa₂ ATPS at pH 5.0, the best recovery and purification factor, 82.4% and 3.59, were obtained. The recovery of NP1 was 98.3% by the separation of ultrafiltration from the PEG-rich phase. The recycling use of GMPNa₂ was also studied, and 95.1% of GMPNa₂ in the salt-rich phase was obtained with the addition of ethanol as the solvent. These results showed that the ATPS was effective for purification of NP1.

Partitioning of Recombinant Pseudomonas putida POS-F84 Proline Dehydrogenase in Aqueous Two-Phase Systems: Optimization Using Response Surface Methodology

Empirical modeling the partition behavior and recovery of a recombinant Pseudomonas putida POS-F84 proline dehydrogenase (ProDH) in aqueous two-phase systems (ATPS) was carried out by response surface methodology (RSM). Polyethylene glycol 1000 (PEG-1000) concentration, sodium carbonate concentration, and pH, which were the most important factors, were chosen for modeling the partition feature of enzyme. The adequacy of the models was investigated by means of variance analysis. Also, to confirm the efficiency of the ATPS in partition and purification of recombinant ProDH, purity and enzymatic activity was studied. After numerical optimization, an optimal ATPS composed of 14.33% PEG-1000 and 11.79% sodium carbonate at pH 7.48 was achieved. Yield, purification factor, and recovery were 81.41%, 60.82, and 270.82%, respectively. Purified recombinant ProDH was found as a single protein band into the upper PEG-rich phase and the specific activity was calculated to be 46.23 ± 2.1 U/mg. Collectively, our data showed that the RSM could be an appropriate and powerful tool to define the best ATPS system for recovery and purification of P. putida ProDH.

Eco-Innovation in Reusing Food By-Products: Separation of Ovalbumin from Salted Egg White Using Aqueous Two-Phase System of PEG 1000/(NH₄)₂SO₄

For the purpose of reducing pollution and the rational use of salted egg white, which is a byproduct of the manufacturing process of salted egg yolk, an aqueous two-phase system (ATPS) composed of polyethylene glycols (PEG 1000) and (NH₄)₂SO₄ was investigated to selectively separate ovalbumin (OVA) from salted egg white. With the aim of optimizing the selective separation of OVA using ATPS, a response surface method (RSM) experiment was carried out on the basis of a single-factor experiment. The OVA was characterized by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS⁻PAGE), reversed-phase high-performance liquid chromatography (RP-HPLC), liquid chromatography-nano electrospray ionization mass spectrometry (Nano LC-ESI-MS/MS), and Fourier transform infrared spectroscopy (FT-IR). Under the optimal conditions, the recovery yield of OVA through ATPS (Y) and the purity of OVA (P) could reach 89.25% and 96.28%, respectively. In conclusion, OVA was successfully separated from the salted egg white by PEG/(NH₄)₂SO₄ ATPS.

Thermo-separating polymer-based aqueous two-phase systems for the recovery of PEGylated lysozyme species

Fractionation of native, mono and di-PEGylated lysozyme was performed in 36 different polymer-polymer aqueous two-phase systems using UCON as a phase-forming component. After a discrete partition analysis, dextran 75 kDa-UCON, volume ratio 3, tie-line length 35% w/w; ficoll 70 kDa-UCON, volume ratio 1, tie-line length 45% w/w and a PEG 8 kDa-UCON volume ratio 3, tie-line length 65% w/w systems were selected for optimization via salt addition and to observe the behavior of the lysozyme species in mixtures. The dextran-UCON and the PEG-UCON systems with 75 mM NaCl showed effectiveness in separating 75% and 87% of mono-PEGylated lysozyme from the rest of the lysozyme species in the top and bottom phases, respectively. These results are an advancement in incorporating these extractions in different processes since the use of UCON simplifies the removal of the polymers, providing the opportunity of recycling it to the operation.

Aqueous two phase partitioning of Pisum sativum lectin in PEG/citrate salt system

Pisum sativum lectin (Psl) is a metalloprotein which is in the center of research interest because of its HIV-1 reverse transcriptase inhibitory activity and mitogenic activity. The application of this lectin in various fields demands the economically feasible and scalable purification strategy other than affinity chromatography. The suitability of aqueous two phase system (ATPS) composed of poly ethylene glycol (PEG) with different salts (sodium citrate, potassium citrate, and ammonium citrate) was evaluated for better partitioning of Psl. The significant factors such as molar mass and concentration of PEG, type and concentration of salts, the effect of tie line length (TLL), ionic strength, and pH were studied to select a suitable system for better partitioning of Psl. ATPS comprising of 18% PEG 6000, 16% sodium citrate, 1% NaCl at the operating condition of pH 8, 40.23% of TLL, and the volume ratio of 1.32 was found to be the best system which gave a maximum partition coefficient and yield of 14.5% and 98.66%, respectively.

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.

Purification and Characterization of Recombinant Human Lysozyme from Eggs of Transgenic Chickens

Transgenic chickens as bioreactors have several advantages, such as the simple establishment procedure, correct glycosylation profile of expressed proteins, etc. Lysozyme is widely used in food industry, livestock farming, and medical field as a replacement of antibiotics because of its antibacterial and complement system-modulating activity. In this study, we used RT-PCR, Western blot, and immunofluorescence to detect the expression of recombinant human lysozyme (rhLY) in the transgenic chicken. We demonstrated that the transgene of rhLY was genetically stable across different generations. We next optimized the purification procedure of rhLY from the transgenic eggs by utilizing two steps of cation-exchange chromatography and one gel-filtration chromatography. About 6 mg rhLY with the purity exceeding 90% was obtained from ten eggs, and the purification efficiency was about 75%. The purified rhLY had similar physicochemical and biological properties in molecular mass and antibacterial activity compared to the commercial human lysozyme. Additionally, both of them exhibited thermal stability at 60°C and tolerated an extensive pH range of 2 to 11. In conclusion, our study proved that the transgenic chickens we have previously generated were genetically stable and suitable for the production of active rhLY. We also provided a pipeline for purifying the recombinant proteins from transgenic eggs, which could be useful for other studies.

Aqueous two phase partitioning of fish proteins: partitioning studies and ATPS evaluation

A suitable Aqueous Two Phase System (ATPS) has been identified for the partitioning of crude fish proteins from fish processing industrial effluent. A detailed study has been performed to analyze the influence of various parameters on protein partitioning such as molecular weight of PEG, effect of different salts (MgSO4, K2HPO4, Na3C6H5O7, Na2SO4, (NH4) 2PO4, K3C6H5O7) and their concentrations, pH, temperature, Tie Line Length (TLL), effluent loading and volume ratio. PEG 2000 - sodium sulphate ATPS was found to be a most favourable system among the selected ATPS for higher partition coefficient of proteins. The binodal curve and equilibrium characteristics of PEG 2000 - sodium sulphate were established and fitted to empirical equations. The equilibrium compositions (tie line) were correlated using Othmer-Tobias and Bancroft equations.

Coupling purification and in situ immobilization process of monoclonal antibodies to clenbuterol for immunosensor application

Clenbuterol (CL), which promotes the growth of muscular tissue and the reduction of body fat in pigs and cattle, has been confirmed to be a potential hazard to human health. In this study, a monoclonal antibody to clenbuterol (CL mAb) from a hybridoma culture supernatant was purified by an aqueous two-phase system (ATPS) at different polyethylene glycol (PEG) concentrations, PEG molecular weights, pH values, and NaCl concentrations. Then the CL mAb was immobilized in situ by directly adding polystyrene microspheres (PSMSs) into a PEG phase containing CL mAb. Using the immobilized antibody, an immunosensor was constructed to detect the CL residues in pork samples. The results showed that using an ATPS composed of 15% (w/w) PEG6000, 15% (w/w) phosphate, and 15% (w/w) NaCl at pH 8.0, the partition coefficient was 7.24, the activity recovery was 87.86%, and the purification fold was 2.88. The PEG-CL mAb-PSMS retained approximately 98% of its initial activity after 30-ml phosphate buffer (PBS) washings. After 30days of storage, the CL mAb-PSMS lost nearly 75% of its activity, whereas the PEG-CL mAb-PSMS retained as much as 95% of its initial activity. Furthermore, the constructed immunosensor obtained recoveries of 90.5 to 102.6% when applied to pork samples spiked with CL.

WITHDRAWN: Optimization of recombinant Pseudomonas putida proline dehydrogenase purification in aqueous two-phase systems using response surface methodology

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Expression, Purification, and Characteristic of Tibetan Sheep Breast Lysozyme Using Pichia pastoris Expression System

A lysozyme gene from breast of Tibetan sheep was successfully expressed by secretion using a-factor signal sequence in the methylotrophic yeast, Pichia pastoris GS115. An expression yield and specific activity greater than 500 mg/L and 4,000 U/mg was obtained. Results at optimal pH and temperature showed recombinant lysozyme has higher lytic activity at pH 6.5 and 45°C. This study demonstrates the successful expression of recombinant lysozyme using the eukaryotic host organism P. pastoris paving the way for protein engineering. Additionally, this study shows the feasibility of subsequent industrial manufacture of the enzyme with this expression system together with a high purity scheme for easy high-yield purification.

All-aqueous multiphase microfluidics

Immiscible aqueous phases, formed by dissolving incompatible solutes in water, have been used in green chemical synthesis, molecular extraction and mimicking of cellular cytoplasm. Recently, a microfluidic approach has been introduced to generate all-aqueous emulsions and jets based on these immiscible aqueous phases; due to their biocompatibility, these all-aqueous structures have shown great promises as templates for fabricating biomaterials. The physico-chemical nature of interfaces between two immiscible aqueous phases leads to unique interfacial properties, such as an ultra-low interfacial tension. Strategies to manipulate components and direct their assembly at these interfaces needs to be explored. In this paper, we review progress on the topic over the past few years, with a focus on the fabrication and stabilization of all-aqueous structures in a multiphase microfluidic platform. We also discuss future efforts needed from the perspectives of fluidic physics, materials engineering, and biology for fulfilling potential applications ranging from materials fabrication to biomedical engineering.

Ionic liquid-salt aqueous two-phase extraction based on salting-out coupled with high-performance liquid chromatography for the determination of sulfonamides in water and food

Ionic liquid-salt aqueous two-phase extraction coupled with high-performance liquid chromatography with ultraviolet detection was developed for the determination of sulfonamides in water and food samples. In the procedure, the analytes were extracted from the aqueous samples into the ionic liquid top phase in one step. Three sulfonamides, sulfamerazine, sulfamethoxazole, and sulfamethizole were selected here as model compounds for developing and evaluating the method. The effects of various experimental parameters in extraction step were studied using two optimization methods, one variable at a time and Box-Behnken design. The results showed that the amount of sulfonamides did not have effect on the extraction efficiency. Therefore, a three-level Box-Behnken experimental design with three factors, which combined the response surface modeling, was used to optimize sulfonamides extraction. Under the most favorable extraction parameters, the detection limits (S/N = 3) and quantification limits (S/N = 10) of the proposed method for the target compounds were achieved within the range of 0.15-0.3 ng/mL and 0.5-1.0 ng/mL from spiked samples, respectively, which are lower than or comparable with other reported approaches applied to the determination of the same compounds. Finally, the proposed method was successfully applied to the determination of sulfonamide compounds in different water and food samples and satisfactory recoveries of spiked target compounds in real samples were obtained.

System establishment of ATPS for one-step purification of glutamate decarboxylase from E. coli after cell disruption

The partition of glutamate decarboxylase (GAD) from Escherichia coli in polyethylene glycol (PEG) and sodium sulfate aqueous two-phase systems (ATPS) has been explored with the purpose of establishing a phase system for the purification of GAD after cell disruption. The results showed that the partitioning of GAD was slightly influenced by PEG molecular weight (MW) but depended on the tie line length (TLL) and NaCl and loading sample concentrations. The optimum system obtained for GAD purification was composed of a PEG MW of 4,000, TLL of 63.5%, a volume ratio of 2.31, a loading sample concentration of 0.4 g/mL, which produced a GAD recovery of 90% with the purification fold of 73. Furthermore, the feasibility of directly purifying GAD from the cell disrupts using ATPS was evaluated. The established ATPS for GAD purification exhibited an efficient integrated purification process compared to the reported purification process in terms of purification efficiency and recovery.