Purification of IgG and albumin from human plasma by aqueous two phase system fractionation

The current shortages in human plasma products at global levels justify the development of new, cost effective plasma fractionation methods. We have developed a fractionation process to obtain immunoglobulin G (IgG) and albumin‐enriched fractions based on polymer‐salt aqueous two phase system (ATPS). A small‐scale (0.02 L) ATPS composed of polyethyleneglycol 3350 (PEG), potassium phosphate and sodium chloride, at pH 6.1, was evaluated and subjected to 50‐fold scale‐up (1 L). Further purification of the fractions was performed using caprylic acid precipitation and ion exchange chromatography. Similar yield and purity were obtained at both small and large scales. IgG precipitated in the PEG rich upper phase at 83% recovery and 2.75‐fold purification factor. An 81% pure albumin fraction was obtained in the salt rich bottom phase with a 91% yield. After polishing, IgG was obtained at a recovery of 70% and a purity of 92%. Corresponding values for albumin were 91% and 90%. This IgG and albumin fractionation technology deserves further evaluation as it may represent a potential alternative to conventional plasma fractionation methods. © 2012 American Institute of Chemical Engineers Biotechnol. Prog., 28: 1005–1011, 2012     

用双水相系统从大肠杆菌细胞内释放L-天门冬酰胺酶

聚乙二醇－磷酸盐双水相系统可以释放大肠杆菌ＡＴＣＣ１１３０３细胞内的Ｌ－天门冬酰胺酶。研究了聚乙二醇、磷酸氢二钾的浓度对酶和蛋白质的释放及分配的影响。在双水相系统中加入适量的盐酸胍和ＴｒｉｔｏｎＸ１００可以提高酶的释放量。实验表明,用新的下相代替富含酶的下相,上相能够重复使用几次。这种方法将酶的释放和萃取结合为一个步骤,使酶的纯化更加简单和有效     

Effect of glycosylation on the partition behavior of a human antibody in aqueous two‐phase systems

Human proteins are expressed in some hosts wrongly glycosylated or nonglycosylated. Although it is accepted that glycosylation contributes to the stability of the protein in solution, the effect of glycosylation on the stability of human antibodies is not fully understood. In this work, we present solubility studies of two human antibodies that have the same primary structure but different glycosylation pattern. The studies were done by monitoring the partitioning behavior of both proteins in a series of aqueous two‐phase systems at and away the isoelectric point of the proteins and at different temperatures. Our studies show that in the absence of direct electrostatic forces, the partitioning behavior of the antibodies depends on the presence or absence of the polysaccharide chains. Overall, the nonglycosylated protein is less soluble than the glycosylated one. The potential of aqueous two‐phase systems for the separation of the glycosylated and nonglycosylated proteins was also explored. A simple series of extractions seems to be enough to separate the glycosylated variety from the nonglycosylated one at high purity but low yields. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 29:943–950, 2013     

Phase separation rates of aqueous two-phase systems: correlation with system properties

The kinetics of phase separation in aqueous two-phase systems have been investigated as a function of the physical properties of the system. Two distinct situations for the settling velocities were found, one in which the light, organic-rich (PEG) phase is continuous and the other in which the heavier, salt-rich (phosphate) phase is continuous. The settling rate of a particular system is a crucial parameter for equipment design, and it was studied as a function of measured viscosity and density of each of the phases as well as the interfacial tension between the phases. Interfacial tension increases with increasing tie line length. A correlation that describes the rate of phase separation was investigated. This correlation, which is a function of the system parameters mentioned above, described the behavior of the system successfully. Different values of the parameters in the correlation were fitted for bottom-phase-continuous and top-phase-continuous systems. These parameters showed that density and viscosity play a role in the rate of separation in both top continuous- and bottom continuous-phase regions but are more dominant in the continuous top-phase region. The composition of the two-phase system was characterized by the tie line length. The rate of separation increased with increasing tie line length in both cases but at a faster rate when the bottom (less viscous) phase was the continuous phase. These results show that working in a continuous bottom-phase region is advantageous to ensure fast separation.     

Type-specific separation of animal cells in aqueous two-phase systems using antibody conjugates with temperature-sensitive polymers.

A new type of aqueous two-phase system (ATPS) has been developed in which a temperature-sensitive polymer, poly-N-isopropylacrylamide [poly (NIPAM)] was used as a ligand carrier for the specific separation of animal cells. Monoclonal antibodies were modified with itaconic anhydride and copolymerized with N-isopropylacrylamide, and the ligand-conjugated carriers were added to the polyethylene glycol 8000-dextran T500 aqueous two-phase systems. The antibody-polymer conjugates were partitioned to the top phase in the absence or presence of 0.15 M NaCl. When ligand-conjugated carriers were used, more than 80% of the cells were specifically partitioned to the top phase in the presence of NaCl up to 0.1 M. The cells were partitioned almost completely to the bottom phase at 0.1 M NaCl or above, when no antibody-conjugate was added in the ATPS. As a model system, CD34-positive human acute myeloid leukemia cells (KG-1) were specifically separated from human T lymphoma cells (Jurkat) by applying anti-CD34 conjugated with poly-N-isopropylacrylamide in the aqueous two-phase system. By the temperature-induced precipitation of the polymer, about 90% of the antibody-polymer conjugates were recovered from the top phase, which gave approximately 75% cell separating efficiency in the next cycle of reuse.     

Isolation of plasmid DNA from cell lysates by aqueous two-phase systems

This work presents a study of the partitioning of a plasmid vector containing the cystic fibrosis gene in polyethylene glycol (PEG)/salt (K2HPO4) aqueous two-phase systems (ATPS). The plasmid was extracted from neutralized alkaline lysates using PEG with molecular weights varying from 200 to 8000. The effects of the lysate mass loaded to the ATPS (20, 40, and 60% w/w) and of the plasmid concentration in the lysate were evaluated. The performance of the process was determined by qualitative and quantitative assays, carefully established to overcome the strong interference of impurities (protein, genomic DNA, RNA), salt, and PEG. Plasmid DNA partitioned to the top phase when PEG molecular weight was lower than 400. The bottom phase was preferred when higher PEG molecular weights were used. Aqueous two-phase systems with PEG 300, 600, and 1000 were chosen for further studies on the basis of plasmid and RNA agarose gel analysis and protein quantitation. The recovery yields were found to be proportional to the plasmid concentration in the lysate. The best yields (>67%) were obtained with PEG 1000. These systems (with 40 and 60% w/w of lysate load) were able to separate the plasmid from proteins and genomic DNA, but copartitioning of RNA with the plasmid was observed. Aqueous two-phase systems with PEG 300 concentrated both plasmid and proteins in the top phase. The best system for plasmid purification used PEG 600 with a 40% (w/w) lysate load. In this system, RNA was found mostly in the interphase, proteins were not detected in the plasmid bottom phase and genomic DNA was reduced 7.5-fold.     

Preparation and recycling of aqueous two‐phase systems with pH‐sensitive amphiphilic terpolymer PADB

In this study, a novel pH‐sensitive terpolymer PADB was synthesized by random terpolymerization of 2‐(dimethylamino) ethyl methacrylate, acrylic acid, and butyl methacrylate. The terpolymer PADB could form aqueous two‐phase systems (ATPS) with a light‐sensitive terpolymer PNBC, which was synthesized in our laboratory, using n‐isopropylacrylamide, n‐butyl acrylate, chlorophyllin sodium copper salt as monomers. More than 97% of the PADB terpolymer could be recovered by adjusting the pH to isoelectric point (PI) 4.1. The terpolymer PNBC could be recovered by using light radiation at 488 nm, with recovery ratio of 98%. BSA and lysozyme were partitioned in the PNBC–PADB ATPS to examine this new system. It was found that the partition coefficient of BSA and lysozyme could reach 4.46 and 0.49 in the systems, respectively. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009     

Effects of chemical modifications in the partition behavior of proteins in aqueous two‐phase systems: A case study with RNase A

Chemical modification of proteins is gaining importance due to the improvement in properties and the broader range of applications that these protein conjugates have. Once modified, several purification strategies need to be applied to isolate the conjugates of interest. Aqueous two‐phase systems (ATPS) are an attractive alternative for the primary recovery of proteins and their conjugates. However, to better understand which biochemical parameters affect in greater degree the partition behavior of these modified proteins in ATPS, it becomes necessary to characterize the partition behavior of different species. In this work, ribonuclease A (RNase A) was selected as a model protein to address the partition behavior of chemically modified proteins in ATPS. Native, mono‐PEGylated, Uniblue A, Dabsyl Chloride, and Direct Red 83 chemically modified RNase A's were partitioned in 16 different polyethylene glycol (PEG)–potassium phosphate ATPS. Results suggest that while the effects of system design parameters govern the partition of native RNase A, the behavior of the chemically modified species is more influenced by the physicochemical characteristics of the modifying molecules, that in most cases promote partition toward the top polymer‐rich phase with recovery percentages as high as 86%. It has been found that both, the hydrophobicity and molecular weight of the modifying species play a preponderant role in conjugate partition behavior since as hydrophobicity increases partition is promoted towards the PEG‐rich phase balancing the effect of the molecular weight of the modifying molecules that tends to shift partition towards the salt rich phase. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 29: 378–385, 2013     

Concentration of mammalian genomic DNA using two‐phase aqueous micellar systems

The concentration of biomarkers, such as DNA, prior to a subsequent detection step may facilitate the early detection of cancer, which could significantly increase chances for survival. In this study, the partitioning behavior of mammalian genomic DNA fragments in a two‐phase aqueous micellar system was investigated using both experiment and theory. The micellar system was generated using the nonionic surfactant Triton X‐114 and phosphate‐buffered saline (PBS). Partition coefficients were measured under a variety of conditions and compared with our theoretical predictions. With this comparison, we demonstrated that the partitioning behavior of DNA fragments in this system is primarily driven by repulsive, steric, excluded‐volume interactions that operate between the micelles and the DNA fragments, but is limited by the entrainment of micelle‐poor, DNA‐rich domains in the macroscopic micelle‐rich phase. Furthermore, the volume ratio, that is, the volume of the top, micelle‐poor phase divided by that of the bottom, micelle‐rich phase, was manipulated to concentrate DNA fragments in the top phase. Specifically, by decreasing the volume ratio from 1 to 1/10, we demonstrated proof‐of‐principle that the concentration of DNA fragments in the top phase could be increased two‐ to nine‐fold in a predictive manner. Biotechnol. Bioeng. 2009;102: 1613–1623. © 2008 Wiley Periodicals, Inc.     

Downstream antibody purification using aqueous two‐phase extraction

The extraction of antibodies using a polyethylene glycol (PEG)‐citrate aqueous two‐phase system (ATPS) was investigated. Studies using purified monoclonal antibody (mAb) identified operating ranges for successful phase formation and factors that significantly affected antibody partitioning. The separation of antibody and host cell protein (HCP) from clarified cell culture media was examined using statistical design of experiments (DOE). The partitioning of antibody was nearly complete over the entire range of the operating space examined. A model of the HCP partitioning was generated in which both NaCl and citrate concentrations were identified as significant factors. To achieve the highest purity, the partitioning of HCP from cell culture fluid into the product containing phase was minimized using a Steepest Descent algorithm. An optimal ATPS consisting of 14.0% (w/w) PEG, 8.4% (w/w) citrate, and 7.2% (w/w) NaCl at pH 7.2 resulted in a product yield of 89%, an approximate 7.6‐fold reduction in HCP levels relative to the clarified cell culture fluid before extraction and an overall purity of 70%. A system consisting of 15% (w/w) PEG, 8% (w/w) citrate, and 15% (w/w) NaCl at pH 5.5 reduced product‐related impurities (aggregates and low molecular product fragments) from ～40% to less than 0.5% while achieving 95% product recovery. At the experimental conditions that were optimized in the batch mode, a scale‐up model for the use of counter‐current extraction technology was developed to identify potential improvements in purity and recovery that could be realized in the continuous operational mode. © 2010 American Institute of Chemical Engineers Biotechnol. Prog., 2010     

Potential application of aqueous two‐phase systems and three‐phase partitioning for the recovery of superoxide dismutase from a clarified homogenate of Kluyveromyces marxianus

Superoxide dismutase (SOD; EC 1.15.1.1) is an antioxidant enzyme that represents the primary cellular defense against superoxide radicals and has interesting applications in the medical and cosmetic industries. In the present work, the partition behavior of SOD in aqueous two‐phase systems (ATPS) (using a standard solution and a complex extract from Kluyveromyces marxianus as sample) was characterized on different types of ATPS (polymer–polymer, polymer–salt, alcohol–salt, and ionic liquid (IL)–salt). The systems composed of PEG 3350‐potassium phosphate, 45% TLL, 0.5 M NaCl (315 U/mg, 87% recovery, and 15.1‐fold purification) and t‐butanol‐20% ammonium sulfate (205.8 U/mg, 80% recovery and 9.8‐fold purification), coupled with a subsequent 100 kDa ultrafiltration stage, allowed the design of a prototype process for the recovery and partial purification of the product of interest. The findings reported herein demonstrate the potential of PEG‐salt ATPS for the potential recovery of SOD. © 2014 American Institute of Chemical Engineers Biotechnol. Prog., 30:1326–1334, 2014     

Extraction of natural red colorants from the fermented broth of Penicillium purpurogenum using aqueous two‐phase polymer systems

Safety concerns related to the increasing and widespread application of synthetic coloring agents have increased the demand for natural colorants. Fungi have been employed in the production of novel and safer colorants. In order to obtain the colorants from fermented broth, suitable extraction systems must be developed. Aqueous two‐phase polymer systems (ATPPS) offer a favorable chemical environment and provide a promising alternative for extracting and solubilizing these molecules. The aim of this study was to investigate the partitioning of red colorants from the fermented broth of Penicillium purpurogenum using an ATPPS composed of poly(ethylene glycol) (PEG) and sodium polyacrylate (NaPA). Red colorants partitioned preferentially to the top (PEG‐rich phase). In systems composed of PEG 6,000 g/mol/NaPA 8,000 g/mol, optimum colorant partition coefficient (K_C) was obtained in the presence of NaCl 0.1 M (K_C = 10.30) while the PEG 10,000 g/mol/NaPA 8,000 g/mol system in the presence of Na₂SO₄ 0.5 M showed the highest K_C (14.78). For both polymers, the mass balance (%MB) and yield in the PEG phase (%η_TOP) were close to 100 and 79%, respectively. The protein selectivity in all conditions evaluated ranged from 2.0–3.0, which shows a suitable separation of the red colorants and proteins present in the fermented broth. The results suggest that the partitioning of the red colorants is dependent on both the PEG molecular size and salt type. Furthermore, the results obtained support the potential application of ATPPS as the first step of a purification process to recover colorants from fermented broth of microorganisms. © 2015 American Institute of Chemical Engineers Biotechnol. Prog., 31:1295–1304, 2015     

Purification of human antibodies from transgenic corn using aqueous two‐phase systems

A recombinant human antibody expressed in corn was purified using aqueous two‐phase extraction. The antibody was an immunoglobulin G fully unglycosylated. Using systems of different compositions and/or pHs in each of one or two partitioning stages followed by one more stage in which the antibody was precipitated at the liquid/liquid interface facilitated the removal of different impurities in each stage. The best system yields a product 72% pure (22‐fold purification) with a yield of 49%. The optimum extraction was done in two partitioning stages followed by an interfacial precipitation stage using poly(ethylene)glycol/potassium phosphate systems. NaCl was added to the first stage to eliminate large molecular weight impurities. The pH in the first stage was kept at 6 but a pH of 8 was used in the second stage and in the precipitation stage. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2010     

Affinity-enhanced protein partitioning in decyl beta-D-glucopyranoside two-phase aqueous micellar systems

Liquid-liquid extraction in two-phase aqueous complex-fluid systems has been proposed as a scalable, versatile, and cost-effective purification method for the downstream processing of biotechnological products. In the case of two-phase aqueous micellar systems, careful choices of the phase-forming surfactants or surfactant mixtures allow these systems to separate biomolecules based on size, hydrophobicity, charge, or specific affinity. In this article, we investigate the affinity-enhanced partitioning of a model affinity-tagged protei--green fluorescent protein fused to a family 9 carbohydrate-binding module (CBM9-GFP)--in a two-phase aqueous micellar system generated from the nonionic surfactant n-decyl beta-D-glucopyranoside (C10G1), which acts simultaneously as the phase-former and the affinity ligand. In this simple system, CBM9-GFP was extracted preferentially into the micelle-rich phase, despite the opposing tendency of the steric, excluded-volume interactions operating between the protein and the micelles. We obtained more than a sixfold increase (from 0.47 to 3.1) in the protein partition coefficient (Kp), as compared to a control case where the affinity interactions were "turned off" by the addition of a competitive inhibitor (glucose). It was demonstrated conclusively that the observed increase in Kp can be attributed to the specific affinity between the CBM9 domain and the affinity surfactant C10G1, suggesting that the method can be generally applied to any CBM9-tagged protein. To rationalize the observed phenomenon of affinity-enhanced partitioning in two-phase aqueous micellar systems, we formulated a theoretical framework to model the protein partition coefficient. The modeling approach accounts for both the excluded-volume interactions and the affinity interactions between the protein and the surfactants, and considers the contributions from the monomeric and the micellar surfactants separately. The model was shown to be consistent with the experimental data, as well as with our current understanding of the CBM9 domain.     

Intensification of mass transfer in aqueous two-phase systems

A novel technique which intensifies conventional aqueous two-phase extraction by conversion of dispersed phase into colloidal gas aphrons (CGAs) has been developed for extraction of an enzyme. In the present work, amyloglucosidase (1,4-alpha-D-glucan glucohydrolase) was extracted using a polyethylene glycol-sodium sulfate-water system. The lighter phase, i.e., polyethylene glycol (PEG) rich phase, was converted into CGAs which were then dispersed into a salt rich phase. The effect of type of surfactant and its concentration, dispersed phase velocity, phase composition, and type of sparger on the dispersed phase mass transfer coefficient was investigated. The results suggests 9-16 times higher values of mass transfer coefficient compared to spray column. The multiorifice sparger at concentrations of 0.33 g/L of cetyl trimethyl ammonium chloride yielded best results. (c) 1993 John Wiley & Sons, Inc.     

Different types of aqueous two‐phase systems for biomolecule and bioparticle extraction and purification

Upstream improvements have led to significant advances in the productivity of biomolecules and bioparticles. Today, downstream processes are the bottleneck in the production of some biopharmaceuticals, a change from previous years. Current purification platforms will reach their physical limits at some point, indicating the need for new approaches. This article reviews an alternative method to extract and purify biomolecules/bioparticles named aqueous two‐phase system (ATPS). Biocompatibility and readiness to scale up are some of the ATPS characteristics. We also discuss some of ATPS applications in the biotechnology field. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 29:1343–1353, 2013     

Foreign protein expression from S phase specific promoters in continuous cultures of recombinant CHO cells

Foreign protein expression from the commonly used SV40 promoter has been found to be primarily during the S-phase of the cell cycle. Simple mathematical models with this cell cycle phase dependent expression of foreign protein suggest that the specific production rate will be proportional to the cell growth rate, which is particularly disadvantageous in high cell density fed-batch or perfusion bioreactors. In this study we investigate this predicted relationship between the production rate and growth rate by culturing recombinant CHO cells in a continuous suspension bioreactor. One CHO cell line, GS-26, has been stably transfected with the plasmid pSVgal, which contains the E. coli lac Z gene under the control of the SV40 promoter. This GS-26 cell line was grown in suspension cultures over a range of specific growth rates in batch and continuous modes. The intracellular -galactosidase activity was assayed using a standard spectrophotometric method after breaking the cells open and releasing the enzyme. A strong growth associated relationship is found between the intracellular -galactosidase content and the specific growth rate in batch and continuous cultures, as predicted.     

Separating lysozyme from bacteriophage P22 in two-phase aqueous micellar systems

This communication demonstrates that two-phase aqueous mixed (nonionic/ionic) micellar systems have the potential for improving the separation of proteins from viruses. Specifically, two separation experiments were performed to show that the addition of the anionic surfactant sodium dodecyl sulfate (SDS) to the two-phase aqueous nonionic n-decyl tetra(ethylene oxide) (C(10)E(4)) micellar system increases the yield of a model net positively charged protein, lysozyme, in the micelle-rich phase from 75 to 95%, while still maintaining approximately the same yield of a model net negatively charged virus, bacteriophage P22, in the micelle-poor phase (97% vs. 98%).     

Correlation for the partition behavior of proteins in aqueous two-phase systems: effect of surface hydrophobicity and charge

Correlations to describe the effect of surface hydrophobicity and charge of proteins with their partition coefficient in aqueous two-phase systems were investigated. Polyethylene glycol (PEG) 4000/phosphate, sulfate, citrate, and dextran systems in the presence of low (0.6% w/w) and high (8.8% w/w) levels of NaCl were selected for a systematic study of 12 proteins. The surface hydrophobicity of the proteins was measured by ammonium sulfate precipitation as the inverse of their solubility. The hydrophobicity values measured correlated well with the partition coefficients, K, obtained in the PEG/salt systems at high concentration of NaCl (r = 0.92-0.93). In PEG/citrate systems the partition coefficient correlated well with protein hydrophobicity at low and high concentrations of NaCl (r = 0.81 and 0.93, respectively). The PEG/citrate system also had a higher hydrophobic resolution than other systems to exploit differences in the protein's hydrophobicity. The surface charge and charge density of the proteins was determined over a range of pH (3-9) by electrophoretic titration curves; PEG/salt systems did not discriminate well between proteins of different charge or charge density. In the absence of NaCl, K decreased slightly with increased positive charge. At high NaCl concentration, K increased as a function of positive charge. This suggested that the PEG-rich top phase became more negative as the concentration of NaCl in the systems increased and, therefore, attracted the positively charged proteins. The effect of charge was more important in PEG/dextran systems at low concentrations of NaCl. In the PEG/dextran systems at lower concentration of NaCl, molecular weight appeared to be the prime determinant of partition, whereas no clear effect of molecular weight could be found in PEG/salt systems.