Characterization of difference in structure and function of fresh and mastitic bovine milk fat globules

Characterization of Cow, Goat, and Water Buffalo Milk Fat Globule Lipids by High-Performance Thin Layer Chromatography

Ruminant milk is an essential part of the human diet and is widely accepted as a major nutrient source in developing countries. However, the polar and neutral lipid content variation in milk fat globules (MFG)among cow, goat, and water buffalo is poorly understood. This study used high-performance thin layer chromatography to identify and quantify five major polar (PL) and three neutral lipids (NL) from the MFG of cow, goat, and water buffalo. Optimal separation was achieved for PLs using chloroform: methanol: water (65:25:4), and hexane: diethyl ether: acetic acid (70:30:1) for NLs. The lower detectable (0.12 to 1.53 μg/mL) and quantification (0.12 to 1.53 μg/mL) limits indicated the high sensitivity of the method. Quantification at 540 nm showed the highest abundance of phosphatidylethanolamine and triglycerides. Fat globules were further characterized for size and microstructural properties, which revealed smaller globules in goats (0.99 ± 0.04 μm) than cows (1.85 ± 0.03 μm) and water buffaloes (2.91 ± 0.08 μm), indicating a negative correlation with PL but a positive correlation with NL. The variation in lipid quantity among different animal species suggests more research to support their selection as a suitable source for developing functional food to impact human health positively.

Serotype-dependent adhesion of Shiga toxin-producing Escherichia coli to bovine milk fat globule membrane proteins

Shiga toxin-producing Escherichia coli (STEC) are food-borne pathogens that can cause severe symptoms for humans. Raw milk products are often incriminated as vehicule for human STEC infection. However, raw milk naturally contains molecules, such as the milk fat globule membrane and associated proteins, that could inhibit pathogen adhesion by acting as mimetic ligands. This study aimed to: (i) evaluate the capability of STEC cells to adhere to bovine milk fat globule membrane proteins (MFGMPs), (ii) highlight STEC surface proteins associated with adhesion and (iii) evaluate the variation between different STEC serotypes. We evaluated the physicochemical interactions between STEC and milk fat globules (MFGs) by analyzing hydrophobic properties and measuring the ζ-potential. We used a plate adhesion assay to assess adhesion between MFGMPs and 15 Escherichia coli strains belonging to three key serotypes (O157:H7, O26:H11, and O103:H2). A relative quantitative proteomic approach was conducted by mass spectrometry to identify STEC surface proteins that may be involved in STEC-MFG adhesion. The majority of E. coli strains showed a hydrophilic profile. The ζ-potential values were between -3.7 and - 2.9 mV for the strains and between -12.2 ± 0.14 mV for MFGs. Our results suggest that non-specific interactions are not strongly involved in STEC-MFG association and that molecular bonds could form between STEC and MFGs. Plate adhesion assays showed a weak adhesion of O157:H7 E. coli strains to MFGMPs. In contrast, O26:H11 and O103:H2 serotypes attached more to MFGMPs. Relative quantitative proteomic analysis showed that the O26:H11 str. 21,765 differentially expressed five outer membrane-associated proteins or lipoproteins compared with the O157:H7 str. EDL933. This analysis also found strain-specific differentially expressed proteins, including four O26:H11 str. 21,765-specific proteins/lipoproteins and eight O103:H2 str. PMK5-specific proteins. For the first time, we demonstrated STEC adhesion to MFGMPs and discovered a serotype effect. Several outer membrane proteins-OmpC and homologous proteins, intimin, Type 1 Fimbriae, and AIDA-I-that may be involved in STEC-MFG adhesion were highlighted. More research on STEC's ability to adhere to MFGMs in diverse biological environments, such as raw milk cheeses and the human gastrointestinal tract, is needed to confirm the anti-adhesion properties of the STEC-MFG complex.

Functional Significance of Different Milk Constituents in Modulating the Gut Microbiome and Infant Health

Human milk, the gold standard for optimal nourishment, controls the microbial composition of infants by either enhancing or limiting bacterial growth. The milk fat globule membrane has gained interest in gut-related functions and cognitive development. The membrane proteins can directly interact with probiotic bacteria, influencing their survival and adhesion through gastrointestinal transit, whereas membrane phospholipids increase the residence time of probiotic bacteria in the gut. The commensal bacteria in milk act as the initial inoculum in building up the gut colonization of an infant, whereas oligosaccharides promote proliferation of beneficial microorganisms. Interestingly, milk extracellular vesicles are also involved in influencing the microbiota composition but are not well-explored. This review highlights the contribution of different milk components in modulating the infant gut microbiota, particularly the fat globule membrane, and the complex interplay between host- and brain-gut microbiota signaling affecting infant and adult health positively.

Shiga Toxin-Producing Escherichia coli and Milk Fat Globules

Shiga toxin-producing Escherichia coli (STEC) are zoonotic Gram-negative bacteria. While raw milk cheese consumption is healthful, contamination with pathogens such as STEC can occur due to poor hygiene practices at the farm level. STEC infections cause mild to serious symptoms in humans. The raw milk cheese-making process concentrates certain milk macromolecules such as proteins and milk fat globules (MFGs), allowing the intrinsic beneficial and pathogenic microflora to continue to thrive. MFGs are surrounded by a biological membrane, the milk fat globule membrane (MFGM), which has a globally positive health effect, including inhibition of pathogen adhesion. In this review, we provide an update on the adhesion between STEC and raw MFGs and highlight the consequences of this interaction in terms of food safety, pathogen detection, and therapeutic development.

Improving Human Health with Milk Fat Globule Membrane, Lactic Acid Bacteria, and Bifidobacteria

The milk fat globule membrane (MFGM), the component that surrounds fat globules in milk, and its constituents have gained significant attention for their gut function, immune-boosting properties, and cognitive-development roles. The MFGM can directly interact with probiotic bacteria, such as bifidobacteria and lactic acid bacteria (LAB), through interactions with bacterial surface proteins. With these interactions in mind, increasing evidence supports a synergistic effect between MFGM and probiotics to benefit human health at all ages. This important synergy affects the survival and adhesion of probiotic bacteria through gastrointestinal transit, mucosal immunity, and neurocognitive behavior in developing infants. In this review, we highlight the current understanding of the co-supplementation of MFGM and probiotics with a specific emphasis on their interactions and colocalization in dairy foods, supporting in vivo and clinical evidence, and current and future potential applications.

BoMiProt: A database of bovine milk proteins

Bovine milk has become an important biological fluid for proteomic research due to its nutritional and immunological benefits. To date, over 300 publications have reported changes in bovine milk protein composition based on seasons, lactation stages, breeds, health status and milk fractions while there are no reports on consolidation or overlap of data between studies. Thus, we have developed a literature-based, manually curated open online database of bovine milk proteome, BoMiProt (http://bomiprot.org), with over 3100 proteins from whey, fat globule membranes and exosomes. Each entry in the database is thoroughly cross-referenced including 397 proteins with well-defined information on protein function, biochemical properties, post-translational modifications and significance in milk from different publications. Of 397 proteins, over 199 have been reported with a structural gallery of homology models and crystal structures in the database. The proteome data can be retrieved using several search parameters such as protein name, accession IDs, FASTA sequence. Furthermore, the proteome data can be filtered based on milk fractions, post-translational modifications and/or structures. Taken together, BoMiProt represents an extensive compilation of bovine milk proteins from literature, providing a foundation for future studies to identify specific milk proteins which may be linked to mammary gland pathophysiology. BIOLOGICAL SIGNIFICANCE: Protein data identified from different previously published proteomic studies on bovine milk samples (21 publications) were gathered in the BoMiProt database. Unification of the identified proteins will give researchers an initial reference database on bovine milk proteome to understand the complexities of milk as a biological fluid. BoMiProt has a user-friendly interface with several useful features, including different search criteria for primary and secondary information of proteins along with cross-references to external databases. The database will provide insights into the existing literature and possible future directions to investigate further and improve the beneficial effects of bovine milk components and dairy products on human health.