Direct capture of lactoferrin from whey using magnetic micro-ion exchangers in combination with high-gradient magnetic separation

Separation Technologies for Whey Protein Fractionation

Whey is a by-product of cheese, casein, and yogurt manufacture. It contains a mixture of proteins that need to be isolated and purified to fully exploit their nutritional and functional characteristics. Protein-enriched fractions and highly purified proteins derived from whey have led to the production of valuable ingredients for many important food and pharmaceutical applications. This article provides a review on the separation principles behind both the commercial and emerging techniques used for whey protein fractionation, as well as the efficacy and limitations of these techniques in isolating and purifying individual whey proteins. The fractionation of whey proteins has mainly been achieved at commercial scale using membrane filtration, resin-based chromatography, and the integration of multiple technologies (e.g., precipitation, membrane filtration, and chromatography). Electromembrane separation and membrane chromatography are two main emerging techniques that have been developed substantially in recent years. Other new techniques such as aqueous two-phase separation and magnetic fishing are also discussed, but only a limited number of studies have reported their application in whey protein fractionation. This review offers useful insights into research directions and technology screening for academic researchers and dairy processors for the production of whey protein fractions with desired nutritional and functional properties.

Aptamer-functionalized pH-responsive polymer-modified magnetic nanoparticles for specific enrichment and sensitive determination of lactoferrin

A new type of aptamer-functionalized pH-responsive polymer-modified magnetic nanoparticles (ApMNPs) is introduced for specific enrichment and sensitive determination of lactoferrin (Lf) in complex matrixes. In the construction, Fe₃O₄@3-(Triethoxysilyl)propylmethacrylate@poly(4-Vinyl-1, 3-dioxolan-2-one-acrylic acid) (Fe₃O₄@MPS@p(VEC-AA)) were synthesized as pH-responsive polymer-modified magnetic nanoparticles (pMNPs) through free radical polymerization to increase the tunable interaction. Lf-binding aptamers were conjugated onto pMNPs through the reaction of amino-group in aptamer and epoxide-group in VEC, innovatively applied to prepare Lf-ApMNPs. On the basis of the synergistic effect of specific affinity of aptamer on Lf and tunable hydrophobic/hydrophilic property of pH-responsive polymer, Lf-ApMNPs presented good selectivity toward Lf, excellent adsorption capacity (as high as 233.9 mg g^-1), as well as good recoveries in the range 93.6-99.6% in Lf-related nutrition samples. Significantly, the introduction of pH-responsive monomer (AA) effectively regulated the adsorption-desorption process of Lf, with the function similar to a switch. Moreover, the good performances of Ct-ApMNPs toward α-Chymotrypsin showed that ApMNPs exhibited universality to other proteins through easily changing the binding aptamer, thereby offering a facile and efficient approach for specific enrichment and sensitive determination of targets in real biological samples.

Application of Ion Exchange and Adsorption Techniques for Separation of Whey Proteins from Bovine Milk

Background:

The world production of whey was estimated to be more than 200 million tons per year. Although whey is an important source of proteins with high nutritional value and biotechnological importance, it is still considered as a by-product of the dairy industry with low economic value due to low industrial exploitation. There are several challenges in the separation of whey proteins: low concentration, the complexity of the material and similar properties (pI, molecular mass) of some proteins.

Methods:

A narrative review of all the relevant papers on the present methodologies based on ion-exchange and adsorption principles for isolation of whey proteins, known to the authors, was conducted.

Results:

Traditional ion-exchange techniques are widely used for the separation and purification of the bovine whey proteins. These methodologies, based on the anion or cation chromatographic procedures, as well as combination of aforementioned techniques are still preferential methods for the isolation of the whey proteins on the laboratory scale. However, more recent research on ion exchange membranes for this purpose has been introduced, with promising potential to be applied on the pilot industrial scale. Newly developed methodologies based either on the ion-exchange separation (for example: simulated moving bed chromatography, expanded bed adsorption, magnetic ion exchangers, etc.) or adsorption (for example: adsorption on hydroxyapatite or activated carbon, or molecular imprinting) are promising approaches for scaling up of the whey proteins’ purification processes.

Conclusion:

Many procedures based on ion exchange are successfully implemented for separation and purification of whey proteins, providing protein preparations of moderate-to-high yield and satisfactory purity. However, the authors anticipate further development of adsorption-based methodologies for separation of whey proteins by targeting the differences in proteins’ structures rather than targeting the differences in molecular masses and pI. The complex composite multilayered matrices, including also inorganic components, are promising materials for simultaneous exploiting of the differences in the masses, pI and structures of whey proteins for the separation.

Magnetic Separation in Bioprocessing Beyond the Analytical Scale: From Biotechnology to the Food Industry

Downstream processing needs more innovative ideas to advance and overcome current bioprocessing challenges. Chromatography is by far the most prevalent technique used by a conservative industrial sector. Chromatography has many advantages but also often represents the most expensive step in a pharmaceutical production process. Therefore, alternative methods as well as further processing strategies are urgently needed. One promising candidate for new developments on a large scale is magnetic separation, which enables the fast and direct capture of target molecules in fermentation broths. There has been a small revolution in this area in the last 10–20 years and a few papers dealing with the use of magnetic separation in bioprocessing examples beyond the analytical scale have been published. Since each target material is purified with a different magnetic separation approach, the comparison of processes is not trivial but would help to understand and improve magnetic separation and thus making it attractive for the technical scale. To address this issue, we report on the latest achievements in magnetic separation technology and offer an overview of the progress of the capture and separation of biomolecules derived from biotechnology and food technology. Magnetic separation has great potential for high-throughput downstream processing in applied life sciences. At the same time, two major challenges need to be overcome: (1) the development of a platform for suitable and flexible separation devices and (2) additional investigations of advantageous processing conditions, especially during recovery. Concentration and purification factors need to be improved to pave the way for the broader use of magnetic applications. The innovative combination of magnetic gradients and multipurpose separations will set new magnetic-based trends for large scale downstream processing.

Magnetic hydrophobic-charge induction adsorbents for the recovery of immunoglobulins from antiserum feedstocks by high-gradient magnetic fishing

BACKGROUND

The extraction of biopharmaceuticals from plasma and serum often employs overly complicated antiquated procedures that can inflict serious damage on especially prone protein targets and which afford low purification power and overall yields. This paper describes systematic development of a high-gradient magnetic fishing process for recovery of immunoglobulins from unclarified antiserum.

RESULTS

Non-porous superparamagnetic particles were transformed into hydrophobic-charge induction adsorbents and then used to recover immunoglobulins from rabbit antiserum feedstocks. Comprehensive characterisation tests conducted with variously diluted clarified antiserum on a magnetic rack revealed that immunoglobulin binding was rapid (equilibrium reached in <45 s), strong (Kd < 0.1 mg mL-1), of high capacity (Qmax = 214 mg g-1), and pH and ionic strength dependent. In a high-gradient magnetic fishing process conducted with the same adsorbent, and a conventional 'magnetic filter + recycle loop' arrangement, >72% of the immunoglobulin present in an unclarified antiserum feed was recovered in 0.5 h in >3-fold purified form.

CONCLUSIONS

Fast magnetic particle based capture of antibodies from an unclarified high-titre feed has been demonstrated. Efficient product recovery from ultra-high titre bioprocess liquors by high-gradient magnetic fishing requires that improved magnetic adsorbents displaying high selectivity, ultra-high capacity and operational robustness are used with 'state-of-the-art' rotor-stator magnetic separators. © 2018 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Purification of equine chorionic gonadotropin (eCG) using magnetic ion exchange adsorbents in combination with high-gradient magnetic separation

Current purification of the glycoprotein equine chorionic gonadotropin (eCG) from horse serum includes consecutive precipitation steps beginning with metaphosphoric acid pH fractionation, two ethanol precipitation steps, and dialysis followed by a numerous of fixed-bed chromatography steps up to the specific activity required. A promising procedure for a more economic purification procedure represents a simplified precipitation process requiring only onethird of the solvent, followed by the usage of magnetic ion exchange adsorbents employed together with a newly designed 'rotor-stator' type High Gradient Magnetic Fishing (HGMF) system for large-scale application, currently up to 100 g of magnetic adsorbents. Initially, the separation process design was optimized for binding and elution conditions for the target protein in mL scale. Subsequently, the magnetic filter for particle separation was characterized. Based on these results, a purification process for eCG was designed consisting of (i) pretreatment of the horse serum; (ii) binding of the target protein to magnetic ion exchange adsorbents in a batch reactor; (iii) recovery of loaded functionalized adsorbents from the pretreated solution using HGMF; (iv) washing of loaded adsorbents to remove unbound proteins; (v) elution of the target protein. Finally, the complete HGMF process was automated and conducted with either multiple single-cycles or multicycle operation of four sequential cycles, using batches of pretreated serum of up to 20 L. eCG purification with yields of approximately 53% from single HGMF cycles and up to 80% from multicycle experiments were reached, with purification and concentration factors of around 2,500 and 6.7, respectively.

Multi-cycle recovery of lactoferrin and lactoperoxidase from crude whey using fimbriated high-capacity magnetic cation exchangers and a novel "rotor-stator" high-gradient magnetic separator

Cerium (IV) initiated "graft-from" polymerization reactions were employed to convert M-PVA magnetic particles into polyacrylic acid-fimbriated magnetic cation exchange supports displaying ultra-high binding capacity for basic target proteins. The modifications, which were performed at 25 mg and 2.5 g scales, delivered maximum binding capacities (Qmax ) for hen egg white lysozyme in excess of 320 mg g(-1) , combined with sub-micromolar dissociation constants (0.45-0.69 µm) and "tightness of binding" values greater than 49 L g(-1) . Two batches of polyacrylic acid-fimbriated magnetic cation exchangers were combined to form a 5 g pooled batch exhibiting Qmax values for lysozyme, lactoferrin, and lactoperoxidase of 404, 585, and 685 mg g(-1) , respectively. These magnetic cation exchangers were subsequently employed together with a newly designed "rotor-stator" type HGMF rig, in five sequential cycles of recovery of lactoferrin and lactoperoxidase from 2 L batches of a crude sweet bovine whey feedstock. Lactoferrin purification performance was observed to remain relatively constant from one HGMF cycle to the next over the five operating cycles, with yields between 40% and 49% combined with purification and concentration factors of 37- to 46-fold and 1.3- to 1.6-fold, respectively. The far superior multi-cycle HGMF performance seen here compared to that observed in our earlier studies can be directly attributed to the combined use of improved high capacity adsorbents and superior particle resuspension afforded by the new "rotor-stator" HGMS design.

Recovery of metallic copper by integrated chemical reduction and high gradient magnetic separation

The recovery of metals from waste effluents is necessary for pollution prevention and sustainable practice. High gradient magnetic separation (HGMS) is seen as a viable method. We investigated the capture of valence copper from aqueous copper ion by HGMS in combination with a chemical reduction process. When a copper solution (3.9 or 15.6 mM) was exposed to excess of dithionite (mole ratio of 1:3) in the presence of ammonia (mole ratio of 4) and amended with MnCl2 (2.5 g/L) and the mixture passed through a flow reactor under a strong magnetic field (10000 Gauss), valence copper was obtained and captured in the reactor with well over 95% yields. The chemical reduction reactions were unaffected by the presence of MnCl2 while the amount of MnCl2 (0, 20 and 32 mM) has significantly varied the copper recovery efficiency, especially in the case of high initial copper ion concentration (15.6 mM). Formation of MnO2 flocs was found to have a detrimental effect on copper removal efficiency. The HGMS method offers a tool of resource recovery for copper from waste effluents.

Influence of different magnetites on properties of magnetic Pseudomonas aeruginosa immobilizates used for biosurfactant production

During the last decades, whole-cell immobilization has been used successfully in many bioprocesses. In particular, it is aimed at implementing continuous production processes, reaching higher production rates, and reusing the biocatalyst. In some cases, effective retention of immobilizates in the bioprocess is not feasible by membranes or sieves due to pore plugging or undesired losses of immobilizates. In the present publication, it is reported about the investigation of magnetic immobilizates of Pseudomonas aeruginosa for application in continuous biosurfactant production of rhamnolipids by foam fractionation and retention of entrained immobilizates by high-gradient magnetic separation from foam. Different materials and methods were tested with respect to important parameters, such as stability, diffusion properties or magnetic separation. Good magnetic separation of immobilizates was achieved at 5% (w/w) magnetite loading. Best results in terms of homogeneous embedding, good diffusion properties, and stability enhancement vis-à-vis pure alginate beads was achieved with alginate beads with embedded Bayoxide magnetite or MagPrep silica particles. Although polyurethane immobilizates showed higher stabilities compared with alginate beads, rhamnolipid diffusion in immobilizates was superior in magnetic alginate beads. Regarding bead production, smaller immobilizates were achieved with suspension polymerization compared to droplet extrusion by the JetCutting technology. In total, magnetic immobilizates are a promising tool for an easier handling of biocatalysts in a continuous biological production process, but they have to be adapted to the current production task.