One-step purification of proteins from chicken egg white using counter-current chromatography

Enzymatic Hydrolysis of Ovotransferrin and the Functional Properties of Its Hydrolysates

Bioactive peptides have great potentials as nutraceutical and pharmaceutical agents that can improve human health. The objectives of this research were to produce functional peptides from ovotransferrin, a major egg white protein, using single enzyme treatments, and to analyze the properties of the hydrolysates produced. Lyophilized ovotransferrin was dissolved in distilled water at 20 mg/mL, treated with protease, elastase, papain, trypsin, or α-chymotrypsin at 1% (w/v) level of substrate, and incubated for 0–24 h at the optimal temperature of each enzyme (protease 55°C, papain 37°C, elastase 25°C, trypsin 37°C, α-chymotrypsin 37°C). The hydrolysates were tested for antioxidant, metal-chelating, and antimicrobial activities. Protease, papain, trypsin, and α-chymotrypsin hydrolyzed ovotransferrin relatively well after 3 h of incubation, but it took 24 h with elastase to reach a similar degree of hydrolysis. The hydrolysates obtained after 3 h of incubation with protease, papain, trypsin, α-chymotrypsin, and after 24 h with elastase were selected as the best products to analyze their functional properties. None of the hydrolysates exhibited antioxidant properties in the oil emulsion nor antimicrobial property at 20 mg/mL concentration. However, ovotransferrin with α-chymotrypsin and with elastase had higher Fe³⁺-chelating activities (1.06±0.88%, 1.25±0.24%) than the native ovotransferrin (0.46±0.60%). Overall, the results indicated that the single-enzyme treatments of ovotransferrin were not effective to produce peptides with antioxidant, antimicrobial, or Fe³⁺-chelating activity. Further research on the effects of enzyme combinations may be needed.

Functional properties of ovotransferrin from chicken egg white and its derived peptides: a review

With emerging trends in the food and pharmaceutical industries, potential applications of egg-derived bioactive compounds were recognized. Ovotransferrin is a major egg white functional protein responsible for multiple bioactivities. The objectives of this review are to provide scientific evidence of the functional properties of chicken ovotransferrin and its derived peptides and to identify future research approaches and applications. Various easy, economical, and non-toxic methods have been reported to produce ovotransferrin with high yield and purity, and chemical and enzymatic approaches have been employed to release bioactive peptides. The native ovotransferrin is known to have antimicrobial, antioxidant, anticancer, and immunomodulatory activities. The peptides produced from ovotransferrin also are reported to have antioxidant, antimicrobial, antihypertensive, and anticancer properties. However, little or no application of these compounds in the food and pharmaceutical areas is available yet. Therefore, the practical application of OTF in nutraceutical and pharmaceutical areas are among the emerging areas of research.

Simultaneous separation of the four major allergens of hen egg white

Hen egg is a worldwide top-consumed food that has attracted public health concerns because it can induce allergic reactions in sensitized individuals. Food allergy investigations need highly purified egg allergens. However, a limited number of purification methods have been described for the combined separation of more than two egg allergens and only few of them have evaluated the immunological activity of these purified proteins. The aim of this work was to develop a chromatographic method for the separation of the four major egg allergens (ovomucoid, ovalbumin, ovotranferrin, and lysozyme) with a demonstrated immunological activity. After a pre-processing step for ovomucin precipitation and pH adjustment, remaining egg white proteins were loaded onto CM-Sepharose column and major egg allergens were separated using cation-exchange chromatography. Yield of ovomucoid, ovalbumin, ovotranferrin, and lysozyme was 60.0%, 52.1%, 29.6%, and 90.2%, respectively. Purified allergens were compared with their commercial standards, showing a high purity as well as a maintained antigenicity. The protocol described in this work is simple, quick, low-cost, and suitable for the study of the immunological properties of these allergens. For higher ovalbumin demand in the lab, 2.1 g ovalbumin can be produced in a single process with high purity.

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.

Optimization of Extraction Parameters for Enhanced Production of Ovotransferrin from Egg White for Antimicrobial Applications

Ovotransferrin is the second most abundant protein (~12-13% of the total egg protein) in egg white after ovalbumin. Ovotransferrin is a potent natural antimicrobial agent as it possesses antibacterial, antifungal, and antiviral properties and is also the major metal binding protein found in egg, which makes it an industrially important protein. Ovotransferrin was extracted from egg white using its metal (iron) binding properties. In the present study, eggs from two different sources were used (fresh local eggs from domestic household source and poultry eggs from shops) to compare the results and Response Surface Methodology was used for the experiment design and data analysis. The following extraction conditions were optimized so as to maximize the yield of ovotransferrin from egg white: ethanol % (v/v) and pH and volume (mL) of 25 mM FeCl₃/50 mL of egg white. A maximum yield of ~85 ± 2.5% was obtained near the optimum extraction conditions. The yield was calculated based on the theoretical value (934 mg) of ovotransferrin in 100 mL of 1.5x diluted egg white solution. Our results suggest that efficient downstream processing may reduce the cost of overall production process of this promising enzyme, making it a natural and cost-effective alternative to the existing chemically synthesized antimicrobial agents.

Sequential separation of lysozyme, ovomucin, ovotransferrin, and ovalbumin from egg white

Ovalbumin, ovotransferrin, ovomucin, and lysozyme are a few of the egg white proteins that can be used as functional components. The objective of this study was to develop a simple, sequential separation method for multiple proteins from egg white. Separated proteins are targeted for human use, and thus any toxic compounds were excluded. The methods for individual components and the sequential separation were practiced in laboratory scale first, and then tested for scale-up. Lysozyme was separated first using FPC3500 cation exchange resin and then ovomucin using isoelectric precipitation. Ovalbumin and ovotransferrin were separated from the lysozyme- and ovomucin-free egg white by precipitating ovotransferrin first using 5.0% (wt/vol) (NH4)2SO4 and 2.5% (wt/vol) citric acid combination. After centrifugation, the supernatant (S1) was used for ovalbumin separation and the precipitant was dissolved in water, and reprecipitated using 2.0% ammonium sulfate (wt/vol) and 1.5% citric acid (wt/vol) combination. The precipitant was used as ovotransferrin fraction, and the supernatant (S2) was pooled with the first supernatant (S1), desalted using ultrafiltration, and then heat-treated to remove impurities. The yield of ovomucin and ovalbumen was >98% and that of ovotransferrin and lysozyme was >82% for both laboratory and scale-up preparations. The SDS-PAGE and western blotting of the separated proteins, except for ovomucin, showed >90% purity. The ELISA results indicated that the activities of separated ovalbumin, ovotransferrin, and lysozyme were >96%. The protocol separated 4 major proteins in sequence, and the method was simple and easily scaled up.

Egg white proteins and their potential use in food processing or as nutraceutical and pharmaceutical agents--a review

Egg white contains many functionally important proteins. Ovalbumin (54%), ovotransferrin (12%), ovomucoid (11%), ovomucin (3.5%), and lysozyme (3.5%) are among the major proteins that have high potentials for industrial applications if separated. The separation methods for these proteins from egg white have been developed since early 1900, but preparation methods of these proteins for commercial applications are still under development. Simplicity and scalability of the methods, use of nontoxic chemicals for the separation, and sequential separation for multiple proteins are very important criteria for the commercial production and application of these proteins. The separated proteins can be used in food and pharmaceutical industry as is or after modifications with enzymes. Ovotransferrin is used as a metal transporter, antimicrobial, or anticancer agent, whereas lysozyme is mainly used as a food preservative. Ovalbumin is widely used as a nutrient supplement and ovomucin as a tumor suppression agent. Ovomucoid is the major egg allergen but can inhibit the growth of tumors, and thus can be used as an anticancer agent. Hydrolyzed peptides from these proteins showed very good angiotensin I converting enzyme inhibitory, anticancer, metal binding, and antioxidant activities. Therefore, separation of egg white proteins and the productions of bioactive peptides from egg white proteins are emerging areas with many new applications.

Rheological Behavior and Organoleptic Effects of Ovalbumin Addition in Yogurt Mousse Production

Yogurt mousse is a novel, high added-value dairy product that has been well received by the market. This paper presents a study of the effect of the addition of ovalbumin to the product on its rheological and organoleptic qualities. The ovalbumin was previously separated from egg white with a high grade of purity using an ion exchange resin synthesized by the authors. Diverse rheological tests at different temperatures and corresponding sensorial assessments were conducted to compare samples without and with added ovalbumin. The obtained results confirm that the product is viscoelastic and combines the properties of foams and emulsions; the elastic component is greater than the viscous component. Moreover, at temperatures ranging from 5 to 15 degrees C, a usual interval of consumption, the product behaves rheologically in a similar way. Conversely, the addition of ovalbumin under the assayed conditions also makes the elastic character of the product increase at a given temperature. Finally, the sensorial assessment tests and determinations of stability and volume yield enabled us to verify that the addition of ovalbumin at an amount of 1.3% hardly alters the stability, resistance to shear stress, or the texture and improves the degree of foaming. Therefore, the product with additive is of good commercial quality.

One-step purification of α-amylase from the cultivation supernatant of recombinant Bacillus subtilis by high-speed counter-current chromatography with aqueous polymer two-phase systems

Purification of alpha-amylase from the cultivation supernatant of recombinant Bacillus subtilis by high-speed counter-current chromatography (HSCCC) in polyethylene glycol (PEG) 4000-inorganic salt aqueous polymer two-phase systems was studied. The effects of sodium chloride concentration on the partition coefficients of alpha-amylase and total protein were respectively tested in PEG4000-phosphate and PEG4000-citrate aqueous polymer two-phase systems to find the proper range of sodium chloride concentration for the HSCCC purification of alpha-amylase. Alpha-amylase was purified from the cultivation supernatant by HSCCC in PEG4000-phosphate system containing 2% (w/w) sodium chloride, yet with considerable loss of activity. PEG4000-citrate aqueous polymer two-phase system containing 2% (w/w) sodium chloride and supplemented with 0.56% (w/w) CaCl2 as protective agent was then successfully applied to purify alpha-amylase from cultivation supernatant by HSCCC to homogeneity and significantly increased the recovery of alpha-amylase activity from around 30 to 73.1%.

Purification of glucosyltransferase from cell-lysate of Streptococcus mutans by counter-current chromatography using aqueous polymer two-phase system

Counter-current chromatography (CCC) using a cross-axis coil planet centrifuge (X-axis CPC) was applied to the purification of glucosyltransferase (GTF) from a cell-lysate of cariogenic bacteria. The purification was performed using an aqueous polymer two-phase system composed of 4.4% (w/w) polyethylene glycol (PEG) 8000-6% (w/w) dextran T500 containing 10mM phosphate buffer at pH 9.2 by eluting the upper phase (UP) at 1.0ml/min. The bacterial GTF in the cell-lysate of Streptococcus mutans was selectively retained in the dextran-rich lower stationary phase. The column contents were diluted and subjected to hydroxyapatite (HA) chromatography to remove the polymers from the GTF. Fractions eluted with 500mM potassium phosphate buffer were analyzed by GTF enzymatic activity as well as sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The GTF purity in the final product was increased about 87 times as that in the cell-lysate with a good recovery rate of about 79% through this purification process.

Purification of lactic acid dehydrogenase from crude bovine heart extract by pH-peak focusing counter-current chromatography

pH-peak focusing counter-current chromatography (CCC) was applied to the purification of lactic acid dehydrogenase (LDH) from a crude bovine heart extract using a cross-axis coil planet centrifuge (CPC). The experiment was performed with two sets of polymer phase systems composed of 16% (w/w) polyethylene glycol (PEG) 1000-12.5% (w/w) potassium phosphate buffer and 15% (w/w) PEG 1540-15% (w/w) ammonium sulfate each at various pH values. The best result was achieved from the PEG 1540-ammonium sulfate polymer phase system by adding a retainer (10 mM acetic acid) to the upper stationary phase and an eluter (100 mM sodium hydroxide) to the lower mobile phase. At a flow-rate of 0.5 ml/min, LDH was eluted as a sharp peak which was well resolved from other proteins. Collected fractions were analyzed by the LDH enzymatic activity and by sodium dodecyl sulfate-polyacrylamide slab gel electrophoresis to detect contaminated proteins. LDH was purified directly from crude bovine heart extract in a concentrated state.

Novel ligands for the affinity-chromatographic purification of antibodies

Affinity chromatography represents one of the most powerful fractionation techniques for the large-scale purification of biotechnological products. Despite its potential, the use of this methodology is limited by the availability of specific ligands for each target. Combinatorial chemistry and molecular modeling, often combined, have become interesting and innovative methods for generating novel ligands, tailored to specific biotechnological needs. One of the greatest area of application has been the discovery of novel ligands for the purification of antibodies, which represent an emerging but very important class of innovative therapeutic agents for the treatment of a vast array of diseases. Naturally available affinity ligands, such as Protein A or G for IgG purification or lectins for IgA and IgM purification, which are obtained from microorganisms or genetically modified bacteria through complex and expensive procedures, are not well suited for large-scale purification and require moreover time-consuming analytical controls to check for the presence of contaminants which may affect the safety of the purified antibody for clinical purposes. Recent results suggest that the application of combinatorial technologies and molecular modeling for the discovery of synthetic ligands may open new avenues for the development of more efficient, less expensive and--more importantly--safer procedures for antibody purification at the industrial level.

Affinity purification of immunoglobulins from chicken egg yolk using a new synthetic ligand

Due to the peculiar composition of the egg yolk and the lack of specific affinity ligands, Y immunoglobulins are normally purified using complex and time consuming procedures involving a combination of precipitation and chromatographic steps first to extract and capture and then to polish IgY. In this study, we have examined the applicability for IgY affinity purification of TG19318, a synthetic ligand for immunoglobulin, obtained from the screening of combinatorial libraries, and already characterized for its capability to purify immunoglobulins of class G, M, E and A. Soluble proteins were separated from the lipidic fraction of egg yolk by the water dilution method and loaded on to TG19318 affinity columns prepared by immobilizing the ligand on the commercially available support Emphaze. In a single chromatographic step TG19318 affinity columns led to an efficient capture of IgY directly from crude samples, and with a purity degree higher than 90%, as determined by densitometric scanning of SDS-PAGE analysis of bound fractions, and with full recovery of antibody activity, as determined by ELISA assay. Higher recovery and purity of IgY was obtained by using loading buffers at pH close to 6.5. Column capacity, determined by applying 4x excess IgY to 1 ml bed volume column, and eluting the retained immunoglobulins, was close to 65 mg of IgY per ml of resin. Chemical and chromatographic stability of TG19318/Emphaze was tested before and after various treatments. The derivatized matrix was found to be very stable, in terms of ligand leakage and maintenance of IgY binding capacity, under conditions of normal column usage, cleaning and storage.