Formation mechanism of mung bean protein amyloid fibril hydrogels via acidic heating

Food amyloid fibrils are innovative nano-biomaterials with high aspect ratios, stable β-sheet structures, and multifunctionality. Mung bean protein is a promising plant protein source for amyloid fibril production owing to its availability and environmental sustainability. Despite recent advances, the effects of protein concentration on the fibrillation process, fibril structural evolution, and gelation behavior of mung bean protein under acidic heating conditions have not been systematically investigated. This work revealed that soft hydrogels could be fabricated through a one-step acidic heating process of mung bean protein solution (2-6%, w/v), and higher protein concentrations accelerated in-situ hydrogel formation and improved their rheological properties. Atomic force microscopy (AFM) analysis showed that high protein concentrations (3-6%) promoted the formation of short, worm-like fibrils, whereas a low concentration (2%) predominantly yielded long, straight fibrils with greater height, contour length, and persistence length. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), thioflavin T (ThT) fluorescence analysis, and circular dichroism (CD) spectroscopy demonstrated that the protein concentration affected fibril growth via modulating hydrolysis, self-assembly, and secondary structure. In addition, the enhanced gel matrix was associated with fibril morphology and higher amyloid structure content at elevated protein concentrations. This work offered valuable insights into the formation mechanism of the multi-scale structure of mung bean protein amyloid fibrils and the assembled hydrogels, highlighting their potential as advanced soft biomaterials for applications in the food industry.