Interaction mechanism between surface layer protein and yeast mannan: Insights from multi-spectroscopic and molecular dynamics simulation analyses

[Display omitted] •The complexation of SLP with mannan was predicted by molecular docking and molecular dynamics simulation.•The quenching mechanism of mannan to SLP belonged to static with high-affinity.•The interaction between mannan and SLP was mainly driven by Hydrophobic forces.•Mannan induced conformational changes of SLP structure.•The SLP-mannan complex was stable and compact. Tibet kefir grain (TKG) formation is mainly dependent on the aggregation of lactobacillus and yeasts. The interaction of surface layer protein (SLP) and yeast mannan plays an important role in mediating the co-aggregation of Lactobacillus kefiri with Saccharomyces cerevisiae. The interaction mechanism of the two was researched through multispectral spectroscopy, morphology observation and silico approaches. Fluorescence spectra data revealed that mannan was bound to SLP through a spontaneous binding process. The particle size of the binding complex increased as the mannan concentration increased. Synchronous fluorescence spectroscopy and circular dichroism (CD) spectra showed the conformational and microenvironment alteration of SLP treated with mannan. Molecular docking results indicated that hydrophobic interactions played major roles in the formation of SLP-mannan complexes. These findings provide a deeper insight into the interactions of protein and polysaccharide, and this knowledge is valuable in the application of SLP and mannan in co-fermentation systems.