Combined processing technologies: Promising approaches for reducing Allergenicity of food allergens

Food allergy is a severe threat to human health. Although processing technologies are widely used to reduce allergenicity, hypoallergenic foods produced by a single processing technology cannot satisfy consumer demands. Combined processing technology (CPT) is a promising strategy for efficiently producing high-quality hypoallergenic foods. This paper reviews the effects of CPT on the allergenicity of food allergens from three aspects: physical-biochemical CPT, biochemical-biochemical CPT, and physical-physical CPT. The synergistic mechanisms, strengths, and limitations of these technologies were discussed. It was found that CPT is generally more effective than single-processing technologies. Physical-biochemical CPT is the most widely studied and well-established because physical and biochemical processing technologies complement each other and effectively disrupt conformational and linear epitopes. Biochemical-biochemical CPT primarily disrupts linear epitopes, but most methods are time-consuming. Physical-physical CPT is the least studied; they mainly disrupt conformational epitopes and only rarely affect linear epitopes.

Processing and inspection of high-pressure microfluidics systems: A review

In the field of microfluidics, high-pressure microfluidics technology, which utilizes high driving pressure for microfluidic analysis, is an evolving technology. This technology combines microfluidics and pressurization, where the flow of fluid is controlled by means of high-pressure-driven devices greater than 10 MPa. This paper first reviews the existing high-pressure microfluidics systems and describes their components and applications. Then, it summarizes several materials used in the microfabrication of high-pressure microfluidics chips, reviewing their properties, processing methods, and bonding methods. In addition, advanced laser processing techniques for the microfabrication of high-pressure microfluidics chips are described. Last, the paper examines the analytical detection methods employed in high-pressure microfluidics systems, encompassing optical and electrochemical detection methods. The review of analytical detection methods shows the different functions and application scenarios of high-pressure microfluidics systems. In summary, this study provides an efficient and advanced microfluidics system, which can be widely used in chemical engineering, food industry, and environmental engineering under high pressure conditions.

Allergenicity assessment of β-lactoglobulin ferulic acid-glucose conjugates

We prepared the β-lactoglobulin (BLG)-ferulic acid (FA)-glucose (Glu) conjugates by alkaline method and Maillard reaction to assess the allergenicity. FA and Glu can form a ternary covalent conjugate with BLG, as evidenced by the shortening of SEC retention time, upward migration of SDS-PAGE protein bands, considerable decrease in free amino and sulfhydryl content, and changes in multistructure. BLG-Glu-FA conjugates weakly bound to immunoglobulin E in allergic sera was weak, reduced interleukin 4 and tumor necrosis factor α levels in RBL-2H3 cells and histamin and interleukin 6 secretion levels in KU812 cells, and inhibited the nuclear factor-κB signaling pathway. In vivo experiments showed that the conjugates regulated T-cell homeostasis in mouse splenic and mesenteric lymphocytes and attenuated splenic and duodenal immune injury. Therefore, the conjugates of BLG with FA combined with Glu altered the epitope structure and exhibited low allergenicity.

The influence on the structure and allergenicity of milk β-lactoglobulin by methylglyoxal during thermal processing

This study aims to investigate the effects of the typical glycation intermediate methylglyoxal (MGO) on the structure and allergenicity of milk β-lactoglobulin (βLG) during thermal processing. Structural changes were assessed using SDS-PAGE, intrinsic fluorescence, circular dichroism, and HPLC-MS/MS. Allergenicity was evaluated through in vitro and in vivo experiments. The conformational changes of βLG significantly were induced by MGO during heat treatment, with a 41.3% decrease in α-helix content and a 25.4% increase in random structure. Furthermore, the lysine, arginine, aspartic acid, and histidine residues in βLG were modified by MGO, which may disrupt or mask allergenic epitopes. Additionally, MGO treatment resulted in a reduction of 41.1% and 26.8% in the pro-inflammatory mediators histamine and β-hexosaminidase in KU812 cells, respectively. Additionally, cytokine levels of IL-4 and IL-13 were reduced by 26.3% and 21.75%, respectively. In mouse experiments, compared to the βLG group, the MGO-βLG group showed a 2-4 fold decrease in IgE, IgG, and IgG1 levels. After reacting with βLG, MGO can reduce serum histamine release by up to 73.9% and mast cell protease-1 (MCP-1) release by 40.8%. These results indicate that the typical glycation intermediate MGO can modify the allergenic epitopes of milk βLG during thermal processing, thereby affecting its allergenicity. This study provides a reference for elucidating the natural rules of allergenicity changes during milk thermal processing.

Characteristics and antioxidant activity of Maillard reaction products from β-lactoglobulin and isomaltooligosaccharide

Starch-derived isomaltooligosaccharide (IMO) is potentially used as prebiotics in infant formulas. Given that they are non-digestible carbohydrates rich in reducing substrates, it's crucial to understand if they can interact with β-lactoglobulin (β-LG) to produce Maillard reaction products (MRPs) and how these MRPs might influence the nutritional properties of β-LG. In our investigation, we conjugated β-LG with IMO to generate MRPs. Using a spectrophotometer, we identified the intermediates and assessed browning. We also evaluated changes in free amino groups and structural alterations. The antioxidative activity of the resulting compounds was assessed using DPPH and the ferric reducing/antioxidant power (FRAP) assay. Our data revealed increased visible absorption and fluorescence intensity, suggesting the formation of intermediate and browning products. The content of free amino groups diminished by 33%, supporting the conjugation of IMO with β-LG. However, circular dichroism results indicated no significant alterations in the secondary structure of β-LG. Notably, the β-LG-IMO MRPs exhibited enhanced 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging activity and ferric reducing/antioxidant power (FRAP). The findings provide insights into the characteristics and antioxidant activities of the conjugates derived from IMO and dairy protein in infant formula.

Modulating the allergenicity and functional properties of peanut protein by covalent conjugation with polyphenols

Peanut protein is a common food allergen. Our previous study demonstrated that the allergenicity of Ara h1 declines after covalent conjugation with polyphenols in vitro; however, how polyphenols affect the structure, function, and allergenicity of peanut protein extract (PPE) after covalent conjugating needs clarifying. Here, we assessed how the structure, function, and allergenicity of PPE changed after covalent conjugation with epigallocatechin-3-gallate (PPE-EGCG) and chlorogenic acid (PPE-CA). PPE covalently conjugated with EGCG and CA using the alkali treatment method. Multi-spectroscopy showed that the structure of PPE-EGCG/CA conjugate changed, becoming less folded. In contrast, the functional properties of PPE significantly improved. The allergenicity of PPE-EGCG/CA significantly declined in vitro and in vivo experiments. Our findings confirm that covalent conjugation of PPE with EGCG and CA reduces the allergenicity and improves the functional properties of PPE by changing the structure of the protein.

Characterization and functional properties of Maillard reaction products of β-lactoglobulin and polydextrose

The Maillard reaction products (MRPs) between polydextrose (PDX), a popular polysaccharide in formula powder, and β-lactoglobulin (β-LG), a major whey protein, were studied in aggregation degree, structure, hydrophobic, antigenic and antioxidant activity changes of β-LG. Incubation of PDX and β-LG (60 ℃, 79% relative humidity) for up to 72 h yielded MRPs with increases in furosine, UV absorbance, fluorescence intensity and loss of free amino groups. High molecular weight β-LG-PDX MRPs were observed by SDS-PAGE. Circular dichroism spectroscopy revealed negligible change in β-LG secondary structure. Changes in the tertiary structure of β-LG were detected by tryptophan fluorescence spectroscopy consistent with an increase in surface hydrophobicity of heated β-LG-PDX. Antigenicity reduction of β-LG in β-LG-PDX reached its peak when heated for 24 h. After heating for 72 h, DPPH radical-scavenging activity of β-LG-PDX increased by 7.4-fold, and the ferric reducing antioxidant power reached 61.1 µmol ascorbic acid/g protein.

High-pressure microfluidization of whey proteins: Impact on protein structure and ability to bind and protect lutein

Dynamic high-pressure homogenization microfluidization (DHPM) is a versatile emerging technology that may be applied to food processing to achieve several goals. DHPM may, depending on nature of the molecules and the working parameters, induce changes in protein structure, which may improve or impair their techno-functional properties and ability to bind other molecules. In this context, DHPM (12 passes, 120 MPa), coupled or not to a cooling device, was applied to β-lactoglobulin (β-lg) and whey protein isolate (WPI) dispersions. Minor changes in the structure of whey proteins were induced by DHPM with sample cooling; although, when sample cooling was not applied, aggregation and increases of around 30% of protein surface hydrophobicity were noticeable for the WPI dispersion. The association constant between the proteins and lutein was in the magnitude of 10⁴ M^-1, and lutein photodegradation constant diminished about 3 times in the presence of proteins, compared to in their absence.

Mechanism of Reduction in Allergenicity and Altered Human Intestinal Microbiota of Digested β-Lactoglobulin Modified by Ultrasonic Pretreatment Combined with Glycation

The effects of ultrasound combined with glycation (UCG) on the allergenicity and human microbial community of β-Lg during in vitro digestion were studied by ELISA, cell experiments, and 16S rRNA high-throughput sequencing. UCG modification and subsequent digestion significantly reduced allergenicity. The decrease in the allergenicity of β-Lg depended not only on the low digestibility of glycated β-Lg, which led to the decrease of some peptides with complete immunogenicity, but also the masking effect of glycation on allergen epitopes of β-Lg. Meanwhile, UCG modification and subsequent digestion could alter the structures of intestinal microbiota and the community abundance at phylum, family, and genus levels, such as Bacteroidota, Fusobacteriota, Enterobacteriaceae, Bacteroidaceae, Ruminococcaceae, Bacteroides, and Faecalibacterium. These results show that simulated in vitro digestion of modified β-Lg reduces allergenicity and alters human intestinal microbiota, which could provide a theoretical basis for studying the relationship between intestinal dysbiosis and cow's milk allergy.

Effects of microfluidization and thermal treatment on the characterization and digestion of curcumin loaded protein–polysaccharide–tea saponin complex nanoparticles

Microfluidization (50–150 MPa) and thermal treatment (45–85 °C) were applied to modulate the stability, molecular interaction and microstructure of zein–proplyene glycol alginate (PGA)–tea saponin (TS) complex nanoparticles for delivery of curcumin.

A new site-specific monoPEGylated β-lactoglobulin at the N-terminal: Effect of different molecular weights of mPEG on its conformation and antigenicity

A new method was investigated to decline the antigenicity of β-Lactoglobulin (β-LG) by site specifically conjugating β-LG at the N-terminus with 5 kDa and 10 kDa monomethoxy polyethylene glycol propyl aldehyde (mPEG-ALD). The optimal reaction conditions were molar ratio of 1:10 (β-LG:mPEG-ALD), reaction time for 16 h, and pH 5.0, and the content of mono-PEGylated β-LG was 51.3%. The results showed that mono-PEGylated β-LG with molecular mass of 23.2 kDa and 28.5 kDa. The peptide fragments of mPEG_5kDa-ALD-β-LG produced the same sequence pattern of β-LG except for the absence of one peptides f(1-14), indicating that α-amino group at the N-terminal was selectively modified. Furthermore, the conformation of modified β-LG underwent into slight change. The antigenicity of mPEG_5kDa-ALD-β-LG and mPEG_10kDa-ALD-β-LG decreased from 144.4 μg/mL to 66.7 and 39.0 μg/mL respectively. It was speculated that the steric hindrance effect of PEG was the main reason for the decline of antigenicity of β-LG.

Six flavonoids inhibit the antigenicity of β-lactoglobulin by noncovalent interactions: A spectroscopic and molecular docking study

It is practical to inhibit the allergenicity of β-lactoglobulin (β-LG) using natural products acting via noncovalent interactions; however, the mechanism of the effect has not been investigated in detail. Herein, the comprehensive noncovalent mechanism of inhibition of the antigenicity of β-LG by six flavonoids (kaempferol, myricetin, phloretin, epigallocatechin-3-gallate (EGCG), naringenin, and quercetin) was investigated by spectroscopic and molecular docking methods. Our results indicate that six flavonoids reduced the antigenicity of β-LG in the following order: EGCG > phloretin > naringenin > myricetin > kaempferol > quercetin, with antigenic inhibition rates of 72.6%, 68.4%, 59.7%, 52.3%, 51.4% and 40.8%, respectively. Six flavonoids induced distinct conformational changes in β-LG, which were closely associated with a decline in antigenicity of β-LG. The flavonoids bound to specific antigen epitopes in the β-sheet and β-turn of β-LG to induce a decrease in the antigenicity of the protein.

Comparison of antigenicity and conformational changes to β-lactoglobulin following kestose glycation reaction with and without dynamic high-pressure microfluidization treatment

Previous work indicated that conformational changes of β-lactoglobulin (β-LG) induced by dynamic high pressure microfluidization (DHPM) was related to the increase of antigenicity. In this study, β-LG glycated with 1-kestose and combined with DHPM decreased the antigenicity of β-LG. The antigenicity of control, β-LG-kestose (0.1 MPa) and β-LG-kestose (80 MPa) were 100, 79 and 42 μg/mL respectively. The molecular weight of β-LG conjugated to kestose increased from 18.4 to 19.6 kDa and its conformation scarcely changed. Conversely, combined with DHPM treatment (80 MPa), β-LG conjugated to kestose formed two conjugates with molecular weight of 18.8 and 19.8 kDa, respectively. Furthermore, the unfolding of β-LG as a result of the treatments is reflected by a decrease of intrinsic and synchronous fluorescence intensity and changes to the secondary structure. The conformational changes induced by DHPM and glycation treatments synergistically decrease the antigenicity of β-LG due to more masked or disrupted epitopes.

The Mechanism of Decreased IgG/IgE-Binding of Ovalbumin by Preheating Treatment Combined with Glycation Identified by Liquid Chromatography and High-Resolution Mass Spectrometry

Ovalbumin is one of the most important sensitizing ingredients in allergens of egg albumin, which restricts the application of egg in the field of food processing. Previous research has indicated that glycation could cause the protein to partially expand, which may bring about the destruction of the structural IgG and IgE epitopes and induce the decline of the IgG- and IgE-binding ability of ovalbumin. In this research, the effect of a preheating treatment integrated with glycation on the IgG- and IgE-binding capability and the conformation changes of ovalbumin was studied by detecting the glycated sites and the values of degree of substitution per peptide (DSP) by liquid chromatography and high-resolution mass spectrometry (LC-HRMS). Interestingly, we found that a glycation site (K227) attached by two ribose molecules was detected in glycated ovalbumin with preheating treatment. In addition, a new glycation site (K323) appeared in G-60. The results displayed that preheating treament could strengthen the changes in the secondary and tertiary structure of ovalbumin by enhancing glycation and further reduce the IgG/IgE-binding ability by integrating with glycation because of the cover of IgG and IgE epitopes. Therefore, preheating treatment integrated with glycation may offer a way for ovalbumin to reduce sensitization.

Glycation of ovalbumin after high-intensity ultrasound pretreatment: effects on conformation, immunoglobulin (Ig)G/IgE binding ability and antioxidant activity

BACKGROUND

Ovalbumin (OVA), a protein with excellent nutritional and processing properties, is the major allergen of hen egg white. High-intensity ultrasound treatment increases the immunoglobulin (Ig)G and IgE binding abilities by unfolding the conformational structure of OVA. This may allow a modification of the IgG and IgE binding of OVA by combining high-intensity ultrasound with other methods, such as glycation, thus representing a promising method for the improvement of protein properties.

RESULTS

Glycation with mannose (M) after ultrasound pretreatment at 0-600 W significantly reduced the IgG and IgE binding abilities and dramatically enhanced the antioxidant activity of OVA-M conjugates, with the lowest values of IgG and IgE binding and highest values of antioxidant capacity observed at 600 W. Polyacrylamide gel electrophoresis showed that the molecular weight of OVA-M conjugates with ultrasound pretreatment increased more than non-pretreatment sample, implying that ultrasound pretreatment promoted glycation. The α-helix content and ultraviolet absorption of OVA were observably increased, whereas β-sheet content, intrinsic fluorescence and surface hydrophobicity were notably decreased, indicating that the tertiary and secondary structures of OVA were markedly changed.

CONCLUSION

High-intensity ultrasound pretreatment can be conducive to reducing the binding abilities of IgG and IgE and enhancing the antioxidant activity of OVA-M conjugates. Therefore, glycation combined with high-intensity ultrasound pretreatment might be a promising method for producing hypo-allergenic and high-antioxidant OVA products. © 2018 Society of Chemical Industry.

The mechanism of reduced IgG/IgE-binding of β-lactoglobulin by pulsed electric field pretreatment combined with glycation revealed by ECD/FTICR-MS

Bovine β-lactoglobulin (β-Lg) is a major allergen existing in milk and causes about 90% of IgE-mediated cow's milk allergies. Previous studies showed that pulsed electric field (PEF) treatment could partially unfold the protein, which may contribute to the improvement of protein glycation. In this study, the effect of PEF pretreatment combined with glycation on the IgG/IgE-binding ability and the structure of β-Lg was investigated. The result showed that PEF pretreatment combined with glycation significantly reduced the IgG and IgE binding abilities, which was attributed to the changes of secondary and tertiary structure and the increase in glycation sites and degree of substitution per peptide (DSP) value determined by electron capture dissociation Fourier transform ion cyclotron resonance mass spectrometry (ECD/FTICR-MS). Unexpectedly, glycation sites (K47, K91 and K135) added by two mannose molecules were identified in glycated β-Lg with PEF pretreatment. Moreover, the results indicated that PEF pretreatment at 25 kV cm^-1 for 60 μs promoted the reduction of IgG/IgE-binding capacity by increasing the glycation degree of β-Lg, whereas single PEF treatment under the same conditions markedly enhanced the IgG/IgE-binding ability by partially unfolding the structure of β-Lg. The results suggested that ECD/FTICR-MS could help us to understand the mechanism of reduction in the IgG/IgE-binding of β-Lg by structural characterization at the molecular level. Therefore, PEF pretreatment combined with glycation may provide an alternative method for β-Lg desensitization.

Reducing the allergenic capacity of β-lactoglobulin by covalent conjugation with dietary polyphenols

To help produce hypoallergenic food, this study investigated reducing the allergenicity and improving the functional properties of bovine β-lactoglobulin (βLG) by covalent conjugation with (-)-epigallo-catechin 3-gallate (EGCG) and chlorogenic acid (CA). The covalent bond between the polyphenols and the amino acid side-chains in βLG was confirmed by MALDI-TOF-MS and SDS-PAGE. Structural analysis by fluorescence spectroscopy, circular dichroism (CD) and Fourier transform infrared (FTIR) indicated that the covalent conjugate of EGCG and CA led to the changed protein structure of βLG. Western blot analysis and enzyme-linked immunosorbent assay indicated that conjugation of βLG with these polyphenols was effective in reducing the IgE-binding capacity of βLG. The conjugates maintained the retinol-binding activity without denaturation the protein and enhanced the thermal stability with high antioxidant activity. The study provides an innovative approach to producing hypoallergenic food.

Glycation of whey proteins: Technological and nutritional implications

Whey proteins are globular proteins that have received much attention due to their high nutritional value and characteristic functional properties. In addition to being part of the protein system in milk, they constitute the main proteins in whey and whey protein products. Interaction of whey proteins with reducing sugars and carbohydrates via Maillard reaction have been extensively studied in milk and in model systems. Glycation of individual whey proteins results in variable increases in their solubility, thermal stability, antioxidant activity, and emulsion and foam stabilization. Limited glycation of whey protein products particularly whey protein isolates (WPI) using polysaccharides has been studied with the aim to produce conjugates with modified functional properties and acceptable sensory properties. An overview is presented here on the effect of glycation on individual whey proteins and whey protein products and the potential uses of the glycated whey proteins.

Mechanism of Reduction in IgG and IgE Binding of β-Lactoglobulin Induced by Ultrasound Pretreatment Combined with Dry-State Glycation: A Study Using Conventional Spectrometry and High-Resolution Mass Spectrometry

Bovine β-lactoglobulin (β-Lg) is one of major allergens in cow's milk. Previous study showed that ultrasound treatment induced the conformational changes of β-Lg and promoted the glycation in aqueous solutions, which is, however, less efficient compared with dry-state. In this work, the effect of ultrasound pretreatment combined with dry-state glycation on the IgG and IgE binding of β-Lg was studied. Dry-state glycation with mannose after ultrasound pretreatment at 0-600 W significantly reduced the IgG and IgE binding of β-Lg, with the lowest values observed at 400 W. The decrease in the IgG and IgE binding of β-Lg was attributed to the increase in glycation extent and the changes of secondary and tertiary structure, which reflected in the increase of UV absorbance, α-helix and β-sheet contents, as well as the decrease of intrinsic fluorescence intensity, surface hydrophobicity, β-turn, and random coil contents. Moreover, ultrasound pretreatment promoted the reduction of IgG and IgE binding abilities by improving glycation, reflecting in the increase of the glycation sites and the degree of substitution per peptide (DSP) value determined by Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). Ultrasound pretreatment at 400 W showed the most significantly enhanced glycation extent. Besides, the results suggested FTICR-MS could provide insights into the glycation at molecular level, which was conducive to the understanding of the mechanism of the reduction in the IgG and IgE binding of β-Lg. Therefore, ultrasound pretreatment combined with dry-state glycation may be a promising method for β-Lg hyposensitization.

The Reduction in the IgE-Binding Ability of β-Lactoglobulin by Dynamic High-Pressure Microfluidization Coupled with Glycation Treatment Revealed by High-Resolution Mass Spectrometry

Our previous study indicated that pretreatment by dynamic high-pressure microfluidization (DHPM) and glycation with galactose was a promising method for decreasing the immunoglobulin E (IgE)-binding ability of β-lactoglobulin (β-LG). In this work, the conformational alteration of β-LG subjected to DHPM and glycation treatment was investigated in relation to IgE-binding ability by orbitrap mass spectrometry. After DHPM pretreatment, lower IgE-binding ability of glycated β-LG was observed with increasing pressures. Prior to DHPM pretreatment, 11 glycated sites were identified, while the number of glycation sites was increased to 12 after pretreatment. However, there was no significant difference of the glycation sites at the pressures of 50, 100, and 200 MPa, respectively. Average degree of substitution per peptide molecule of β-LG (DSP) was investigated to assess the degree of glycation per glycation site. All of the samples pretreated by DHPM exhibited a higher glycation level than those without DHPM pretreatment. The shielding effects of epitopes owing to glycation contributed to the reduction of IgE-binding capacity. Orbitrap mass spectrometry could provide a comprehensive understanding of the nature of protein glycation.

Glycation of β-lactoglobulin under dynamic high pressure microfluidization treatment: Effects on IgE-binding capacity and conformation

The effects of dynamic high-pressure microfluidization (DHPM) (80, 120, and 160MPa) treatment and glycation with galactose on the IgE-binding capacity and conformation of β-lactoglobulin (β-Lg) were investigated. The binding capacity of immunoglobulin E (IgE) from patients' sera with cow's milk allergy on β-Lg glycated with galactose decreased after DHPM treatment. β-Lg treated after different DHPM methods and pressures yielded a significant discrepancy in IgE-binding capacity. When β-Lg was pretreated by DHPM, the IgE-binding capacity of β-Lg-galactose conjugates decreased with increasing pressure; however, the conjugates showed higher IgE-binding capacity at 120MPa than that at 80 and 160MPa when the β-Lg-galactose mixture was treated by DHPM. Results of thermal properties, intrinsic fluorescence spectroscopy, surface hydrophobicity, and circular dichroism (CD) spectra indicated the occurrence of protein unfolding, as well as the tertiary and secondary structural changes of β-Lg. The results suggested pretreatment by DHPM and glycation with galactose was a promising approach for eliminating the IgE-binding capacity of β-Lg.

β-Lactoglobulin mutant Lys69Asn has attenuated IgE and increased retinol binding activity

β-Lactoglobulin (β-LG) is a member of lipocalin superfamily of transporters for small hydrophobic molecules such as retinoids, fatty acids, drugs, and vitamins. β-LG also is one of the major allergens in milk. Despite a lot of research on decreasing cow's milk allergenicity, the effects of mutations of β-LG on recognition by IgE from cow's milk allergy (CMA) patients have not been investigated. We describe here the expression in the yeast Pichia pastoris of a mutant bovine β-LG, in which lysine at position 69, in the main epitopes of the protein, was changed into asparagine (Lys69Asn). The purity and native like folded structure of the recombinant Lys69Asn β-LG was confirmed by HPLC, SDS-PAGE, mass spectrometry and circular dichroism. Lys69Asn β-LG has a fourfold stronger affinity than the wild-type protein for retinol, palmitic acid, and resveratrol, as determined by quenching of the intrinsic tryptophan fluorescence. At the same time the Lys69Asn mutant had a 9 fold attenuated, compared with the wild-type, affinity for IgE of sera from patients suffering from cow's milk allergy, whereas no difference could be detected between mutant and wild-type for binding of the IgGs of four monoclonal antibodies. The results of this study demonstrated the significant role of Lys69 residue on the binding and immuoreactivity properties of β-LG.

β-lactoglobulin mutation Ala86Gln improves its ligand binding and reduces its immunoreactivity

β-Lactoglobulin (β-LG) is a member of lipocalin superfamily of transporters for small hydrophobic molecules. β-LG is also one of the major allergens in milk. Despite a lot of researches on decreasing of cow's milk allergenicity, the effects of the mutation of β-LG on its recognition by IgE from cow's milk allergy (CMA) patients have not been investigated. We described here the expression in the yeast Pichia pastoris of a mutant β-LG, in which Alanine 86 was changed into Glutamine (Ala86Gln; a mutation on one of the major epitopes of the protein). The purity and native like folded structure of the recombinant Ala86Gln have been demonstrated using circular dichroism, HPLC, SDS-PAGE and mass spectrometry. The effect of the mutation on the binding of IgE from CMA patients to mutant protein was evaluated by ELISA methods and the results showed that the mutation of Ala-86 was associated with weaker binding of IgE from CMA patients to Ala86Gln mutant protein. Subsequently, the binding of various ligands such as retinol, palmitic acid, resveratrol and serotonin, with native, recombinant wild type and Ala86Gln mutant β-LGs were investigated by fluorescence spectroscopy and an improvement on the binding affinity of the mutated protein to various ligands was observed.