Protein-Dominated Adsorption and Protection on Viruses in Model EPS Components: Insight from Multiscale Mechanistic Analysis

Abstract Extracellular polymeric substances (EPS) as the core sewage sludge components play important roles in floc stability and pollutant adsorption. However, the molecular mechanisms underlying EPS–virus interactions and their environmental implications remain unclear. This study employed three representative model EPS components, i.e., proteins, polysaccharides, and humic substances, and systematically investigated EPS–virus interaction mechanisms with T7 bacteriophage as a virus surrogate. By integrating surface plasmon resonance analysis, double-layer agar plaque assays and qPCR, we demonstrated that proteins dominate virus adsorption and stability within simulated EPS matrices. With rapid protein–virus association (ka up to 106 M–1·s–1) and moderate binding affinities (KD in the 10–6–10–7 M range), roughly 60% of viral infectivity was preserved over 8 days, in contrast to the 4.58% observed in the control. By integrating Extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) theory, Fourier transform infrared spectroscopy, and molecular dynamics simulations, we further elucidated that adsorption is primarily governed by van der Waals forces, with electrostatic, hydrophobic, and hydrogen-bond interactions also involved. Moreover, the protein conformational rearrangements upon adsorption may further facilitate the formation of stable complexes. These findings provide mechanistic insights into the fate and potential EPS-mediated risks of viruses in engineered and natural aquatic environments, and also offer a theoretical basis for improving viral risk assessment.