Microplastics-Induced Binding and Structural Changes in the Milk Proteins: α -Lactalbumin and β -Lactoglobulin

Microplastics (MPs) pollution poses a global threat to ecosystems, human health, and biodiversity conservation. Among the most common contaminants in both terrestrial and aquatic environments are Polyvinyl Chloride Microplastics (PVC-MPs), Polyethylene Microplastics (PE-MPs), and Polystyrene Microplastics (PS-MPs). The two main whey proteins in milk are α -lactalbumin (α-LA), and β -lactoglobulin (β-LG). They are important to food science, nutrition, and overall health. Because PVC-MPs, PE-MPs, and PS-MPs are highly accessible to animals, they breakdown slowly in the atmosphere, accumulate in the bloodstream of mammals, and can be transferred to breast milk, causing serious health problems. Multispectroscopic investigations were used in this work to evaluate the interaction between the developing pollutants PVC-MPs, PE-MPs, and PS-MPs and α-LA and β-LG under physiologically simulated conditions. According to multispectroscopic investigations, α-LA adsorbed onto MPs in the following order: PE>PS>PVC (KA= 7.74, 5.54, and 5.50 ˟ 106 M-1 respectively) and for β-LG, PS>PVC>PE (KA= 9.21, 6.33, and 3.72˟ 106 M-1 respectively). Once PVC-MPs, PE-MPs, and PS-MPs reach the breastmilk, their small size may allow them to adsorb and bind with α-LA and β-LG, probably changing their physiological function and structure. These findings also imply that PE-MPs and PS-MPs, respectively, stimulate amyloid fibrils in α-LA and β-LG. Furthermore, the results demonstrated that PVC-MPs, PE-MPs, and PS-MPs dramatically changed the secondary structure and microenvironment of α-LA and β-LG, which reduced the α-helix and the interaction is static, exothermic, and electrostatic in nature. In addition to offering vital information about the intermolecular interactions, this work elucidates the potential effects of MPs in milk.