Comparing the structure and functionality of amyloid fibrils assembled from peanut, pea, lentil, and mung bean proteins

Protein structure dictates functionality, and one way to dramatically alter protein structure is to induce proteins to self-assemble into amyloid fibrils. Amyloid fibrils, or nanofibrils, are long (100–1000’s nm), narrow (10’s nm), highly-organized protein aggregates that hold promise for various applications in biotechnology and food. Converting plant proteins into fibrils may improve their functionality and create sustainable materials, yet most nanofibril research has focused on animal-derived proteins, so there is a need to learn more about fibrils derived from plant proteins. This project compared fibrils assembled from crude protein extracts from peanut, pea, lentils and mung bean, comparing their fibril assembly kinetics, fibril structure, emulsification and viscosity properties. Peanut and mung bean fibrils assembled much faster (kPeanut = 0.90 ± 0.40 h-1, kMungbean = 0.95 ± 0.40 h-1) compared to pea and lentil fibrils (kPea = 0.19 ± 0.03 h-1, kLentil = 0.24 ± 0.01 h-1), at 80 °C, pH 2 with stirring. Fibrils from the different legume proteins displayed markedly different structures that could be generally classified as either long and straight (1000’s nm) or short and curly (100’s nm). The former are more similar to fibrils typically generated from animal proteins (e.g., whey, egg white proteins) while the latter are typical of legume protein fibrils presented in the literature. The longer/straighter or shorter/curly fibrils displayed unique functionalities (emulsion particle size and viscosity profiles) that did not directly correlate with fibril morphology, although several confounding factors limit the establishment of direct structure-function associations. This work indicates several approaches to optimize the assembly of legume protein fibrils that may find use in new plant-based materials and foods.