On-column refolding of denatured lysozyme by the conjoint chromatography composed of SEC and immobilized recombinant DsbA

DsbA (disulfide bond formation protein A) located in the periplasm of Escherichia coli is a disulfide isomerase, which is vital to disulfide bonds formation directly affecting the nascent peptides folding to the correct conformation. In this paper, recombinant DsbA was firstly immobilized onto NHS-activated Sepharose Fast Flow gel. Then Sephadex G-100 gel was sequentially packed on the top of recDsbA Sepharose Fast Flow, and a so-called conjoint chromatography column composed of SEC and immobilized recombinant DsbA was constructed. Denatured lysozyme was applied on the conjoint column. The effect of SEC volume, flow rate, loading amount and volume, pre-equilibrium mode and KCl concentration in the buffer on lysozyme refolding were investigated in detail and the stability of DsbA immobilization was evaluated. Finally the reusability of the conjoint refolding column was also tested. When loading 2.4 mg denatured lysozyme in 0.5 ml solution, the activity recovery reached 92.7% at optimized experimental conditions, and the conjoint column renaturation capacity decreased only 7.7% after six run reuse due to the use of SEC section in the chromatographic refolding process. The conjoint chromatography offers an efficient strategy to refold proteins in vitro with high productivity and column reusability.     

Refolding and purification of recombinant human interferon-γ expressed as inclusion bodies inEscherichia coli using size exclusion chromatography

A size exclusion chromatography (SEC) process, in the presence of denaturant in the refolding buffer was developed to refold recombinant human interferon-γ (rhIFN-γ) at a high concentration. The rhIFN-γ was overexpressed inE. coli, resulting in the formation of inactive inclusion bodies (IBs). The IBs were first solubilized in 8 M urea as the denaturant, and then the refolding process performed by decreasing the urea concentration on the SEC column to suppress protein aggregation. The effects of the urea concentration, protein loading mode and column height during the refolding step were investigated. The combination of the bufferexchange effect of SEC and a moderate urea concentration in the refolding buffer resulted in an efficient route for producing correctly folded rhIFN-γ, with protein recovery of 67.1% and specific activity up to 1.2×10⁷ IU/mg.     

Refolding of recombinant human interferon ��-2a from Escherichia coli by urea gradient size exclusion chromatography

Protein refolding is still a puzzle in the production of recombinant proteins expressed as inclusion bodies (IBs) in Escherichia coli. Gradient size exclusion chromatography (SEC) is a recently developed method for refolding of recombinant proteins in IBs. In this study, we used a decreasing urea gradient SEC for the refolding of recombinant human interferon ??-2a (rhIFN??-2a) which was overexpressed as IBs in E. coli. In chromatographic process, the denatured rhIFN??-2a would pass along the 8.0?C3.0 M urea gradient and refold gradually. Several operating conditions, such as final concentration of urea along the column, gradient length, the ratio of reduced to oxidized glutathione and flow rate were investigated, respectively. Under the optimum conditions, 1.2 × 10⁸ IU/mg of specific activity and 82% mass recovery were obtained from the loaded 10 ml of 1.75 mg/ml denatured protein, and rhIFN??-2a was also purified during this process with the purity of higher than 92%. Compared with dilution method, urea gradient SEC was more efficient for the rhIFN??-2a refolding in terms of specific activity and mass recovery.     

High recovery refolding of rhG-CSF from Escherichia coli, using urea gradient size exclusion chromatography

Protein folding liquid chromatography (PFLC) is a powerful tool for simultaneous refolding and purification of recombinant proteins in inclusion bodies. Urea gradient size exclusion chromatography (SEC) is a recently developed protein refolding method based on the SEC refolding principle. In the presented work, recombinant human granulocyte colony-stimulating factor (rhG-CSF) expressed in Escheriachia coli (E. coli) in the form of inclusion bodies was refolded with high yields by this method. Denatured/reduced rhG-CSF in 8.0 mol.L(-1) urea was directly injected into a Superdex 75 column, and with the running of the linear urea concentration program, urea concentration in the mobile phase and around the denatured rhG-CSF molecules was decreased linearly, and the denatured rhG-CSF was gradually refolded into its native state. Aggregates were greatly suppressed and rhG-CSF was also partially purified during the refolding process. Effects of the length and the final urea concentration of the urea gradient on the refolding yield of rhG-CSF by using urea gradient SEC were investigated respectively. Compared with dilution refolding and normal SEC with a fixed urea concentration in the mobile phase, urea gradient SEC was more efficient for rhG-CSF refolding--in terms of specific bioactivity and mass recovery, the denatured rhG-CSF could be refolded at a larger loading volume, and the aggregates could be suppressed more efficiently. When 500 microL of solubilized and denatured rhG-CSF in 8.0 mol.L(-1) urea solution with a total protein concentration of 2.3 mg.mL(-1) was loaded onto the SEC column, rhG-CSF with a specific bioactivity of 1.0 x 10(8) IU.mg(-1) was obtained, and the mass recovery was 46.1%.     

On-column refolding of recombinant human interferon-gamma with an immobilized chaperone fragment

The chaperone mini-GroEL is a soluble recombinant fragment containing the 191-345 amino acid sequence of GroEL with a 6xHis tag. The refolding protocol assisted with mini-GroEL was studied for the activity recovery of rhIFN-gamma inclusion bodies. In a suspended system, mini-GroEL showed significant enhancement of the activity recovery of rhIFN-gamma, applyed with a 1-5:1 stoichiometry of mini-GroEL to rhIFN-gamma at 25 degrees C. Moreover, 1 M urea in the renaturation buffer had a synergistic effect on suppressing the aggregation and improving the activity recovery. Finally, a novel chromatographic column, containing 1 cm height of Sephadex G 200 at the top of column and packed with immobilized mini-GroEL to promote refolding, was devised. The total activity recovered per milligram of denatured rhIFN-gamma was up to 3.93 x 10(6) IU with the immobilized mini-GroEL column, which was reused four times without evident loss of renaturation ability. A convenient technique with the integrated process of chaperon preparation and rhIFN-gamma folding in vitro was developed.     

High productivity refolding of an inclusion body protein using pulsed-fed size exclusion chromatography

Protein refolding using size exclusion chromatography (SEC) is advantageous over conventional refolding methods in terms of ease of automation, simultaneous purification capabilities, and the non-adsorptive protein–matrix interaction which eliminates steric constraints. Despite these advantages, the widespread use of SEC refolding remains restricted by low process productivity and product concentration bottlenecks. This study aims to address those limitations and exploit SEC advantages for large-scale refolding applications. Specifically, this study reports the development of a pulsed-fed size exclusion chromatography (PF-SEC) refolding platform, which successfully refolded E. coli-derived α-fetoprotein (AFP) to achieve 53% refolding yield at 0.9 mg/ml AFP refolding concentration. AFP was introduced into the column by pulsed injection to increase feed load, while suppressing concentration-induced aggregation. Refolding was initiated by a urea gradient in the column, where the gradient length could be readily adjusted to complement pulsed feeding patterns. AFP refolding productivity with PF-SEC improved by 8- and 64-fold compared to ion-exchange chromatography refolding and pulsed dilution refolding, respectively, at a fixed refolding concentration. Through a unique integration of pulsed feeding and urea gradient development, this new PF-SEC refolding methodology overcomes ‘productivity and concentration’-related disadvantages inherent in SEC, and will be scalable for large-scale protein refolding applications.     

Refolding strategies for ketosteroid isomerase following insoluble expression in Escherichia coli

Dilution and column-based protein refolding techniques are compared for refolding Delta 5-3-ketosteroid isomerase (KSI) with a C-terminus his6-tag. Column refolding was performed by removing the denaturant while the protein was adsorbed in an immobilized metal affinity chromatography column. Both dilution refolding and a single-step column-based refolding strategy were optimized to maximize the recovery of KSI enzyme activity, and achieved refolding yields of 87% and 70% respectively. It was found that the column-based refolding yield was reduced at higher adsorbed protein concentrations. An elution gradient with increasing imidazole concentration was used to selectively elute the biologically active KSI protein following column refolding, with high molecular weight KSI aggregates retained in the column. An iterative column-refolding process was then developed to denature and refold protein retained in the column, which significantly increased the refolding yield at high-adsorbed protein concentrations. Repetition of the column refolding operation increased the refolding yield from 50% to 75% for protein adsorbed at a concentration of 2.9 mg/mL of adsorbent. Although for the KSI protein column-based refolding did not improve the overall refolding yield compared to dilution refolding, it may still be advantageous due to the ease of integration with purification operations, increased control over the refolding conditions, and the ability to segregate refolded protein from inactive aggregates during elution.     

Development and scale‐up of a commercial fed batch refolding process for an anti‐CD22 two chain immunotoxin

We describe the development and scale‐up of a novel two chain immunotoxin refolding process. This work provides a case study comparing a clinical manufacturing process and the commercial process developed to replace it. While the clinical process produced high quality material, it suffered from low yield and high yield variability. A systematic approach to process development and understanding led to a number of improvements that were implemented in the commercial process. These include a shorter inclusion body recovery process, limiting the formation of an undesired deamidated species and the implementation of fed batch dilution refolding for increased refold titers. The use of a combination of urea, arginine and DTT for capture column cleaning restored the binding capacity of the capture step column and resulted in consistent capture step yields compared to the clinical process. Scalability is shown with data from 250 L and 950 L scale refolding processes. Compared to the clinical process it replaces, the commercial process demonstrated a greater than fivefold improvement in volumetric productivity at the 950 L refolding scale. © 2014 American Institute of Chemical Engineers Biotechnol. Prog., 30:1380–1389, 2014     

A Comparative Investigation on Different Refolding Strategies of Recombinant Human Tissue-type Plasminogen Activator Derivative

Recombinant human tissue-type plasminogen activator derivative (r-PA), fused with thioredoxin (Trx), was expressed in Escherichia coli. The resultant fusion protein, Trx-r-PA, was almost completely in the form of inclusion bodies and without activity. Different refolding strategies were investigated including different post-treatment of solubilized Trx-r-PA inclusion bodies, on-column refolding by size-exclusion chromatography (SEC) using three gel types (Sephacryl S-200, S-300 and S-400), refolding by Sephacryl S-200 with a urea gradient and two-stage temperature control in refolding. An optimized on-column refolding process for Trx-r-PA inclusion bodies was established. The collected Trx-r-PA inclusion bodies were dissolved in 6 m guanidine hydrochloride (Gdm·HCl), and the denatured protein was separated from dithiothreitol (DTT) and Gdm·HCl with a G25 column and simultaneously dissolved in 8 m urea containing oxidized glutathione (GSSG). Finally a refolding of Trx-r-PA protein on Sephacryl S-200 column with a decreasing urea gradient combined with two-stage temperature control was employed, and the activity recovery of refolded protein was increased from 3.6 to 13.8% in comparison with the usual dilution refolding. Revisions requested 31 October 2005; Revisions received 20 December 2005     

Fluorimetric study of the artificial chaperone-assisted renaturation of carbonic anhydrase: a kinetic analysis

It is now well accepted that ionic detergents along with alpha- or beta-cyclodextrins can enhance protein refolding yields. In this report, we evaluated the effect of detergent's tail length on the kinetics of denatured carbonic anhydrase refolding along with determining the rate-limiting step of the whole refolding process. A sensitive fluorimetric technique was also developed to follow up the second-by-second fate of the denatured protein while undergoing refolding. In this technique, inclusion complexes are formed between the correctly refolded CA and the fluorescent active site probe, 5-dimethylaminonaphtalene-1-sulfonamide. By this specific technique, it became evident that the rate of detergent stripping from the CA-detergent mixed micelles that also appeared to be the rate-limiting step depends on the beta-CD-detergent association constants which are under the influence of detergent's tail length. Based on these findings, appropriate refolding conditions could be designed to kinetically diminish the rate of off-pathway aggregation.     

蛋白质的排阻色谱复性的新进展

外源蛋白在大肠杆菌中高效表达时 ,常常形成不溶的、无活性的包涵体 ,包涵体蛋白的复性是重组蛋白生产过程中的一个技术难题。排阻色谱 (sizeexclusionchromatography ,SEC)用于蛋白复性是一种较新的、适用于任何一种蛋白的方法 ,与常用的稀释复性法相比 ,它能在高的起始蛋白浓度下对蛋白进行复性 ,活性回收率较高 ,同时又能使目标蛋白得到一定程度的纯化。对使用SEC复性的进展进行了评述 ,其内容包括SEC复性的原理及其复性过程中的影响因素 ,并对其未来发展进行了展望。     

Effects of the IbpAB AND ClpA chaperones on DnaKJE-dependent refolding of bacterial luciferases in Escherichia coli cells

The rate and level of DnaKJE-dependent refolding of the thermoinactivated Aliivibrio fischeri luciferase are considerably lower in Escherichia coli ibpA and ibpB mutants than in wild type cells. The rate and level of refolding are lower in E. coli ibpB::kan than in ibpA::kan cells. The decline of refoldings level in E. coli clpA::kan makes progress only with the increase of thermoinactivation time of luciferase. Plasmids with the genes ibpAB don't compensate clpA mutation. It is supposed that small chaperones IbpAB and chaperone ClpA operate independently in a process of DnaKJE-dependent refolding of proteins at the different stages.     

In vitro refolding of porcine pepsin immobilized on agarose beads

Since in vitro refolding of pepsin has long been attempted without success, it has been suspected that pepsin has no intrinsic refolding ability. In the present study, in order to eliminate unfavorable intermolecular interactions bringing about aggregation and autoproteolysis, we immobilized pepsin onto agarose beads. This technique enabled us to search extensively for appropriate refolding conditions without limitation of the refolding period. Renaturation of immobilized pepsin was observed exclusively at pH 3-5. This process was extremely slow and reached equilibrium after 300 h. Sixty percent of the proteolytic activity was recovered at pH 5. Addition of salts raised the recovery to 80% but had no significant effect on the refolding rate, suggesting that the salts mainly stabilize the native state of pepsin. This is the first report on the successful in vitro refolding of pepsin.     

Effect of column dimensions and flow rates on size-exclusion refolding of beta-lactamase

We have investigated the effect of changing the column diameter and length on the size exclusion chromatography (SEC) refolding of beta-lactamase from Escherichia coli-derived inclusion bodies (IBs). Inclusion bodies were recovered and solubilised in 6 M GdnHCl and 5 mM DTT. Up to 16 mg of denatured, solubilised beta-lactamase was loaded onto size exclusion columns packed with Sephacryl S-300 media (fractionation range: 10(4)-1.5 x 10(6) Da). beta-Lactamase was refolded by eluting the loaded sample with 1 M urea in 0.05 M phosphate buffer, pH 7 at 23 degrees C. The following columns were studied: 26 x 400, 16 x 400 and 26 x 200 mm, with a range of mobile phase flow rates from 0.33 to 4.00 ml/min. beta-Lactamase was successfully refolded in all three columns and at all flow rates studied. The beta-lactamase activity peak coincided with the major protein peak. Reducing the column diameter had little effect on refolding performance. The enzyme activity recovered was relatively independent of the mobile phase linear velocity. Reducing the column length gave a poorer resolution of the protein peaks, but the enzyme activity peaks were well resolved. Calculation of the partition coefficients for beta-lactamase activity showed that the 26 x 400 column gave the greatest refolding performance.     

Predictions of matrix‐assisted refolding of α‐lactalbumin: Process efficiency versus batch dilution method

Protein refolding is an important technique to produce active recombinant proteins from inclusion bodies. Because of the complexity of the refolding process, a trial‐and‐error method is usually used for its design, which is ineffective and time consuming. Therefore, an efficient method for the process prediction is indispensable to optimize the operating conditions. In this article, we suggest a design procedure for matrix‐assisted protein refolding. Three different chromatographic techniques were considered exploiting hydrophobic interaction chromatography, ion‐exchange chromatography, and SEC media. The procedure consisted of quantification of refolding kinetics, analysis of the retention behavior of all protein forms involved in refolding, construction of a dynamic model, and the process simulation. Denatured bovine α‐lactalbumin was used as model protein. The refolding rate was measured for different protein concentration using the batch dilution method. A kinetic scheme for the protein refolding was suggested and incorporated into a dynamic model of chromatographic column and used for predicting the refolding performance. The productivity, yield, and buffer consumption were used as performance indicators for the refolding techniques considered. The matrix‐assisted protein refolding process outperformed batch dilution method with respect to all indicators provided that efficient method for the process design was used.     

Inhibition of aggregation by media selection,sample loading and elution in size exclusion chromatographic refolding of denatured bovine carbonic anhydrase B

The effects of gel media, sample application and elution flowrate on the activity recovery and aggregation in refolding of bovine carbonic anhydrase B (CAB) by size exclusion chromatography (SEC) were investigated. Variation in aggregation was demonstrated visibly by the comparison of refolding profiles under different operating conditions. Some principles with regard to practical application were proposed. Meanwhile, the analysis of relationship between peak resolution and activity recovery provided evidences for the mechanism of size exclusion chromatography protein refolding.     

大肠杆菌表达的单链抗体柱复性的研究

对包含体表达的抗乙肝病毒表面抗原（HBsAg）的单链抗体（ScFv）纯化复性进行了探索.尝试了利用金属螯合亲和层析和凝胶层析柱进行柱上在位复性的可行性. 对包含体表达的ScFv进行透析复性与柱复性,比较其相对复性率及蛋白质回收率,发现柱上复性效果优于传统的透析复性.抗HBsAg ScFv经凝胶色谱Sephacyl S-200柱复性的相对复性率为98%, 蛋白质回收率为81%.由于将纯化复性同步进行,简化了操作程序,提高了产品的回收率.     

Influence of solvent conditions on refolding of bovine serum albumin

The effect of solvent conditions on the refolding of bovine serum albumin was studied. The rate and extent of refolding was affected by the type of monovalent salt used in the medium. While NaCl and NaBr promoted refolding, NaClO4 and NaSCN decreased the rate and extent of refolding at 0.2 M concentration. In this respect the relative order in which various anions influenced the refolding process followed the lyotropic series Cl-, Br-, I-, ClO4-, SCN-. Urea exhibited two opposite effects on the refolding of albumin: whereas at low concentrations urea increased the extent of refolding, at concentrations above 2.0 M the rate and extent of refolding were dramatically decreased. Addition of ethanol to the medium greatly decreased the refolding even at concentrations as low as 4% (v/v). The effects of these various additives on the refolding behavior of serum albumin is interpreted in terms of subtle changes in the structure of water. It is also shown that, while such changes in the solvent structure affected the rate and extent of refolding, they did not affect the pathway of refolding.     

Examination of protein adsorption in fluidized bed and packed bed columns at different temperatures using frontal chromatographic methods

The influences of various experimental parameters on the dynamic adsorption capacity (DAC) and the dynamic adsorption rate (DAR) of a biomimetic affinity silica-based adsorbent in fluidized and packed bed columns operated under plug flow conditions and at different temperatures have been investigated with different inlet concentrations of hen egg white lysozyme (HEWL) and human serum albumin (HSA). The DACs as well as the DARs of both the fluidized and packed beds were examined at 10% saturation (i.e., at the QB value) and the experimental data compared with the corresponding data obtained from batch equilibrium adsorption procedures. Parameters examined included the fluid superficial velocity and protein concentration and their effect on the binding capacity and column efficiency. Consistent with various results reported from this and other laboratories on the behavior of biospecific affinity adsorbents derived from porous silica and zirconia particles, adsorbents prepared from Fractosil 1000 were found to exhibit appropriate rheological characteristics in fluidized bed systems under the experimental conditions. Moreover, changes in temperature resulted in a more significant effect on the breakthrough profiles of HSA compared to HEWL with the immobilized Cibacron Blue F3G-A with Fractosil 1000 adsorbent. This result suggests that temperature effects can possibly be employed profitably in some processes as part of a strategy to enhance column performance with fluidized bed systems for selective recovery of target proteins. At relatively low superficial velocities of the feed, the DARs with HEWL and HSA were similar for both the fluidized and packed bed column systems, whereas, at high superficial velocities, the DARs for these proteins were larger with the packed bed columns.     

Acyl cystamine: small-molecular foldase mimics accelerating oxidative refolding of disulfide-containing proteins

Based on the structural characteristic of Protein disulfide isomerases and DsbA that have hydrophobic regions around the active sites, hydrophobic alkyl tails are linked to cystamine to create new small molecular foldase mimics, acyl cystamine. Both the oxidizing power and oxidation specificity of cystamine are enhanced by n-octanoyl or n-hexanoyl tail. N-octanoyl and n-hexanoyl cystamine are very effective to facilitate oxidative protein refolding at strong reducing environments. In the presence of 0.42 mM DTT, the activity recovery of lysozyme is over 90% by 90-min refolding with 0.1 mM n-octanoyl cystamine and 0.1 mM cystamine as oxidant, while almost no activity is recovered with 0.2 mM GSSG by 160-min refolding. For the refolding of 0.2 mg/mL lysozyme, with 0.6 mM n-hexanoyl cystamine and 1.12 mM residual DTT as redox agents, the activity recovery reaches as high as 93% after refolding for only 20 min. For ribonuclease A (RNase A) refolding, with 0.4 mM n-hexanoyl cystamine and 1.30 mM DTT, the recovery of activity reaches as high as 90% within 3 h. Thus, with n-octanoyl or n-hexanoyl cystamine as the oxidants, the necessity to remove excess DTT in the reduced and denatured protein solutions can be greatly alleviated. With a moderate hydrophobicity, n-hexanoyl cystamine is promising for application in oxidative protein refolding at an extensive concentration range. It is observed that in the oxidative refolding of 0.2 mg/mL lysozyme and RNase A, only about half of n-hexanoyl cystamine is needed when compared to cystamine to achieve the same kinetic effect.