Abstract
The whey protein beta-lactoglobulin is the building block of amyloid fibrils which exhibit a great potential in various applications. These include stabilization of gels or emulsions. During biotechnological processing, high shear forces lead to fragmentation of fibrils and therefore to smaller fibril lengths. To provide insight into such processes, pure straight amyloid fibril dispersions (prepared at pH 2) were produced and sheared using the rotor stator setup of an Ultra Turrax. In the first part of this work, the sedimentation properties of fragmented amyloid fibrils sheared at different stress levels were analyzed with mulitwavelength analytical ultracentrifugation (AUC). Sedimentation data analysis was carried out with the boundary condition that fragmented fibrils were of cylindrical shape, for which frictional properties are known. These results were compared with complementary atomic force microscopy (AFM) measurements. We demonstrate how the sedimentation coefficient distribution from AUC experiments is influenced by the underlying length and diameter distribution of amyloid fibrils.In the second part of this work, we show how to correlate the fibril size reduction kinetics with the applied rotor revolution and the resulting energy density, respectively, using modal values of the sedimentation coefficients obtained from AUC. Remarkably, the determined scaling laws for the size reduction are in agreement with the results for other material systems, such as emulsification processes or the size reduction of graphene oxide sheets.
Highlights
Amyloid fibrils are found in various fields including medicine, nanotechnology, material science and food science (Knowles and Mezzenga 2016; Cao and Mezzenga 2019)
Molecular dynamics simulations of the densification of fibril‐like structures
Fibril structures were analyzed and density changes were retrieved from the molecular dynamics (MD) simulations
Summary
Amyloid fibrils are found in various fields including medicine, nanotechnology, material science and food science (Knowles and Mezzenga 2016; Cao and Mezzenga 2019). The length distribution of amyloid fibrils involved in diseases has a strong impact on. Smith et al (2015) and Tarutani et al (2016) assume that fragmented amyloid-like aggregated fibrils play a key role in pathogenic seeds for prion-like conversion. Functional fibril structures are highly interesting, especially for food applications. The high length-to-height ratio in combination with specific functional groups on the surface makes fibrils from whey proteins an interesting additive for gels, foams and emulsions as stabilizing, emulsifying or gelling agents (Humblet-Hua et al 2012; Veerman et al 2003). It is known that fragmentation leads to a slight alteration of the functionality of long fibrils by weakening electrostatic interactions and changing solution properties such as viscosity and effective volume (Koo et al 2018)
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