A Comprehensive Identification of Chicken Egg White Phosphoproteomics Based on a Novel Digestion Approach

Characteristics of exopolysaccharides - egg white protein composite gel and its application in low - fat sausage

A composite gel was developed by integrating antioxidant extracellular polysaccharides (EPS) derived from Pediococcus acidilactici S1 with egg white protein (EWP), aiming to evaluate its potential as a viable alternative to animal fat in pork sausages. The results indicated that the EPS - EWP gel exhibited a lower free water content, an enhanced water - holding capacity, a higher apparent viscosity, and increased storage and loss modulus. Molecular interactions were strengthened, resulting in a more stable structure characterized by the transition of secondary structure from random coils to ordered β - sheets. Molecular docking (MD) analysis revealed favorable binding conformations and strong binding energies between ovalbumin (OVA) and EPS, particularly through the formation of specific pockets involving interactions with residues such as Lysine (Lys) and Aspartic acid (Asp). Hydrophobic and electrostatic forces were identified as the primary driving forces for this energetic combination. Additionally, low - fat sausages showed a significant 32.87 % improvement in inhibiting fat oxidation.

Ovotransferrin, an alternative and potential protein for diverse food and nutritional applications

Ovotransferrin(OVT)is a protein found in many types of egg white and has a wide range of functional properties. It has 50% homology with human/bovine lactoferrin, and is expected to be one of the most important alternative proteins for use in food and nutritional applications. This paper mainly reviews the structural characteristics and chemical properties of OVT, as well as its extraction and purification methods. It also systematically describes the various biological activities of OVT and its applications in food and medical industries. The challenges and limitations in the research of OVT were suggested. This review recommends some possible methods such as nanoparticle carriers and microencapsulation to improve the bioavailability and stability of OVT. In addition, this review highlights several strategies to overcome the limitations of OVT in terms of preparation and purification. This review systematically summarizes the recent advances in OVT and will provide guidance for the its development for food and nutritional applications.

Protein aggregation caused by pasteurization processing affects the foam performance of liquid egg white

Pasteurization is necessary during the production of liquid egg whites (LEW), but the thermal effects in pasteurization could cause an unavoidable loss of foaming properties of LEW. This study intended to investigate the mechanism of pasteurization processing affects the foam performance of LEW. The foaming capacity (FC) of LEW deteriorated significantly (ΔFCmax = 72.33 %) and foaming stability (FS) increased slightly (ΔFSmax = 3.64 %) under different temperature-time combinations of pasteurization conditions (P < 0.05). The increased turbidity and the decreased solubility together with the decreased absolute value of Zeta potential indicated the generation of thermally induced aggregates and the instability of the protein particles, Rheological characterization demonstrated improved viscoelasticity in pasteurization liquid egg whites (PLEW), explaining enhanced FS. The study revealed that loss in foaming properties of PLEW resulted from thermal-induced protein structural changes and aggregation, particularly affecting FC. This provided a theoretical reference for the production and processing of LEW products.

Dry-heat-induced phosphoserine-specific fragmentation of ovalbumin

When subjected to dry-heating, egg white ovalbumin, a phosphoglycoprotein, undergoes fragmentation and forms soluble aggregates. We investigated the mechanisms of dry-heat-induced fragmentation of ovalbumin. SDS-PAGE analysis showed that ovalbumin fragmented into five polypeptides, and their amount increased over 6 h of dry-heat treatment at 120 °C. The fragments contained fewer or no phosphoserine, compared with that in crude ovalbumin. Liquid chromatography-tandem mass spectrometry analysis of tryptic digests revealed that the fragmentation sites were located on phosphoserine residues, S68 and S344. During fragmentation, the phosphoserine residues underwent conversion into dehydroalanine residues, which were subsequently hydrolyzed. The nitrogen from the dehydroalanine became a newly formed terminal amide group on the N-terminal fragment, while the remaining molecule predominantly formed a new terminal pyruvoyl group. Furthermore, the fragments were incorporated into monomers or soluble aggregates of ovalbumin via covalent and non-covalent bonds. This study demonstrated a novel mechanism for dry-heat-induced fragmentation of phosphoproteins.

Characterization of the interactions between Fulvic acid and Trypsin with Spectroscopic and Molecular Docking technology

The interaction mechanism between trypsin and fulvic acid was analyzed by multispectral method and molecular docking simulation. The fluorescence spectra showed that fulvic acid induced static quenching of trypsin. The validity of this conclusion was further substantiated through the computation of the binding constants. The thermodynamic parameters show that the reaction is mainly controlled by van der Waals force and hydrogen bond force, and the reaction is spontaneous. In addition, based on the obtained binding distance, there may be a non-radiative energy transfer between the two. The ultraviolet spectrum showed that fulvic acid could shift the absorption peak of trypsin, indicating that fulvic acid had an effect on the secondary structure of trypsin. According to the synchronous fluorescence spectrum results, fulvic acid primarily interacts with tryptophan residues in trypsin and induces alterations in their microenvironment. Three-dimensional fluorescence spectrum and circular dichroism further proves this conclusion. The molecular docking simulation reveals that the interaction between the two groups primarily arises from hydrogen bonding and van der Waals forces. The findings suggest that FA has the ability to induce conformational changes in trypsin's secondary structure.

Phosphoproteomic insight into the changes in structural proteins of muscle architecture associated with texture softening of grass carp (Ctenopharyngodon idella) fillets during chilling storage

Texture is an important sensory attribute of fish affected by modifications of structural proteins in muscle architecture. To investigate the changes in protein phosphorylation during texture softening of fish, the proteins of grass carp muscle after chilling storage of 0 day and 6 days were compared by phosphoproteomics, and their association with texture was analyzed. Totally 1026 unique phosphopeptides on 656 phosphoproteins were identified as differential. They were mainly classified as intracellular myofibril and cytoskeleton, and extracellular matrix, of which the molecular function and biological process were binding into supramolecular assembly and myofilament contraction. The concomitant dephosphorylation of kinases and assembly regulators indicated dephosphorylation and disassembly tendency of sarcomeric architecture. Correlation analysis defined the relation between texture and dephosphorylation of myosin light chain, actin, collagen and cytoskeleton. This study revealed that protein phosphorylation may affect the texture of fish muscle through regulating sarcomeric assembly of structural proteins in muscle architecture.

Phosphoproteomics Profile of Chicken Cecum in the Response to Salmonella enterica Serovar Enteritidis Inoculation

Salmonella enterica serovar Enteritidis (S. Enteritidis) is a foodborne pathogen, which can cause great threats to human health through the consumption of contaminated poultry products. This research combines TMT labeling, HPLC and mass-spectrometry-based phosphoproteomics on cecum of the F1 cross of Guangxi Yao chicken and Jining Bairi chicken. The treated group was inoculated with 0.3 mL inoculum S. Enteritidis, and the control group was inoculated with 0.3 mL phosphate-buffered saline (PBS). A total of 338 differentially phosphorylated modification sites in 243 differentially phosphorylated proteins (DPPs) were chosen for downstream analyses. A total of 213 sites in 146 DPPs were up-regulated and 125 sites in 97 DPPs were down-regulated. Functional analysis was performed for DPPs based on gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, and the protein domain. The DPPs were mainly enriched in immune- and metabolic-related GO-BP (biological process) and KEGG pathways. We predicted and classified the subcellular structure and COG/KOG of DPPs. Furthermore, protein-protein interaction network analyses were performed by using multiple algorithms. We identified 71 motifs of the phosphorylated modification sites and selected 18 sites randomly to detect the expression level through parallel reaction monitoring (PRM). S. Enteritidis inoculation caused phosphorylation alteration in immune- and metabolic-related proteins. The invasion of S. Enteritidis may be actualized by inducing cecum cell apoptosis through the endoplasmic reticulum pathway, and chickens could resist the invasion of S. Enteritidis by affecting the function of ECM receptors. The findings herein provide a crucial theoretical foundation to understand the molecular mechanism and epigenetic regulation in response to S. Enteritidis inoculation in chickens.

Unveiling and application of the chicken egg proteome: An overview on a two-decade achievement

Egg proteins are not only the most complete and ideal form of protein for human or embryo nutrition but also play the vital role in the food industry. Egg proteins are subjected to many potential changes under various conditions, which may further alter the nutritional value, physicochemical-properties, and bioactivities of proteins. Recent advances in our understanding of the proteome of raw egg matrix from different species and dynamic changes occurring during storage and incubation are developing rapidly. This review provides a comprehensive overview of the main characteristics of chicken egg proteome, covering all its components and applications under various conditions, such as markers detection, egg quality evaluation, genetic and biological unknown identification, and embryonic nutritional supplementation, which not only contributes to our in-depth understanding of each constituent functionality of proteome, but also provides information to increase the value to egg industry.

Functional Properties and Extraction Techniques of Chicken Egg White Proteins

Chicken egg whites contain hundreds of proteins, and are widely used in the food, biological and pharmaceutical industries. It is highly significant to study the separation and purification of egg white proteins. This review first describes the structures and functional properties of several major active proteins in egg whites, including ovalbumin, ovotransferrin, ovomucoid, lysozyme, ovomucin, ovomacroglobulin and avidin. Then, the common techniques (including precipitation, chromatography and membrane separation) and some novel approaches (including electrophoresis, membrane chromatography, aqueous two-phase system and molecular imprinting technology) for the separation and purification of egg white proteins broadly reported in the current research are introduced. In addition, several co-purification methods for simultaneous separation of multiple proteins from egg whites have been developed to improve raw material utilization and reduce costs. In this paper, the reported techniques in the last decade for the separation and purification of chicken egg white proteins are reviewed, discussed and prospected, aiming to provide a reference for further research on egg proteins in the future.

Antimicrobial Proteins and Peptides in Avian Eggshell: Structural Diversity and Potential Roles in Biomineralization

The calcitic avian eggshell provides physical protection for the embryo during its development, but also regulates water and gaseous exchange, and is a calcium source for bone mineralization. The calcified eggshell has been extensively investigated in the chicken. It is characterized by an inventory of more than 900 matrix proteins. In addition to proteins involved in shell mineralization and regulation of its microstructure, the shell also contains numerous antimicrobial proteins and peptides (AMPPs) including lectin-like proteins, Bacterial Permeability Increasing/Lipopolysaccharide Binding Protein/PLUNC family proteins, defensins, antiproteases, and chelators, which contribute to the innate immune protection of the egg. In parallel, some of these proteins are thought to be crucial determinants of the eggshell texture and its resulting mechanical properties. During the progressive solubilization of the inner mineralized eggshell during embryonic development (to provide calcium to the embryo), some antimicrobials may be released simultaneously to reinforce egg defense and protect the egg from contamination by external pathogens, through a weakened eggshell. This review provides a comprehensive overview of the diversity of avian eggshell AMPPs, their three-dimensional structures and their mechanism of antimicrobial activity. The published chicken eggshell proteome databases are integrated for a comprehensive inventory of its AMPPs. Their biochemical features, potential dual function as antimicrobials and as regulators of eggshell biomineralization, and their phylogenetic evolution will be described and discussed with regard to their three-dimensional structural characteristics. Finally, the repertoire of chicken eggshell AMPPs are compared to orthologs identified in other avian and non-avian eggshells. This approach sheds light on the similarities and differences exhibited by AMPPs, depending on bird species, and leads to a better understanding of their sequential or dual role in biomineralization and innate immunity.

Effect of high intensity ultrasound assisted glycosylation on the gel properties of ovalbumin: Texture, rheology, water state and microstructure

In this paper, the effects of ultrasonic assisted glycosylation on the gel properties of ovalbumin (OVA) were studied. The molecular characteristics of native ovalbumin, heated ovalbumin, traditional glycosylated ovalbumin, ultrasonic ovalbumin and ultrasonic assisted glycosylated ovalbumin were compared. The lowest free amino group content and the highest browning intensity indicated that ultrasonic can facilitate the Maillard reaction. The gel hardness of ultrasonic glycosylation and the traditional heating glycosylation groups individually increased to 653.2 and 526.9 g compared with the control (344.9 g). The transformation of protein structure was confirmed by FTIR and fluorescence spectrum, which prompted negatively charged groups to reach the protein surface and form more disulfide bond in sOVA-X gel. The interaction between the water and the protein was strengthened, thereby increasing the water holding capacity. These results supplied a theoretical basis for the application of ultrasonic to improve protein properties.

Effect of sodium tripolyphosphate on the interaction and aggregation behavior of ovalbumin-lysozyme complex

The mechanism by which sodium tripolyphosphate affected the aggregation behavior of ovalbumin-lysozyme complexes was investigated in this work. The highest stability coefficients were detected for natural ovalbumin and lysozyme at pH 9.0 and pH 5.0, with values of 0.981 and 0.931, respectively. The turbidity of the phosphorylated ovalbumin-lysozyme complexes was 1.71-fold to the natural complexes at pH 7.0. This result was related to the fact that the phosphorylated sample had a lower isoelectric point. Besides, both intermolecular forces and SDS-PAGE analysis indicated that the disulfide bond was the most important interaction in the complex. Circular dichroism analysis showed that phosphorylation weakened the unfolding and stretching of the structure caused by heat treatment. Moreover, transmission electron microscopy pictures confirmed that the network structure of phosphorylated ovalbumin-lysozyme complex was broader than natural protein. This study provides information for further understanding the effect of phosphorylation on protein aggregation behavior.