The Effect of Limited Proteolysis by Trypsin on the Formation of Soy Protein Isolate Nanofibrils

Abstract

Nanofibril system constructed by protein self-assembly is widely used in the food industry because of purposive functional properties. Soy protein isolate nanofibrils (SPINs) were reported to form via heating at pH 2.0. In this research, the soy protein isolate (SPI) hydrolysate prepared by trypsin was used as a raw material for the formation of nanofibrils called soy protein isolate hydrolysate nanofibrils (SPIHNs). Microscopic images demonstrated the formation of two nanofibrils. Based on circular dichroism spectroscopy and Thioflavin T (ThT) fluorescence spectral, we concluded that β-sheet played an important role in SPIN and SPIHN’s structural composition. At the same time, the α-helix in SPI had not been destroyed, thereby favoring the formation of SPIHN. The surface hydrophobicity of SPIHN continued to increase during the heating process and reached the highest value when heating 8 h. SDS-PAGE analysis showed that peptides produced by enzyme-modified SPI affected the formation of SPIHN. These results proposed that enzymatic hydrolysis prior to acidic during fibrillation process affected the fibrillation of SPI, and the peptides formed by enzymatic hydrolysis were more efficient for the self-assembly process. This study will provide a theoretical basis for the future research of SPI nanofibril functionality.

Nanofibrils of food‐grade proteins: Formation mechanism, delivery systems, and application evaluation

“…With respect to the morphology of nanofibrils, SPI tended to form long and semiflexible nanofibrils, while the β‐conglycinin hydrolysates tended to produce short and worm‐like nanofibrils when both SPI and β‐conglycinin hydrolysates were heated at pH 2.0 and 90°C for 60 min, respectively (Xia et al., 2017). Based on these viewpoints, we used the SPI hydrolysates obtained by trypsin to fabricate nanofibrils at pH 2.0 and 85°C and determined the properties of the resulting nanofibrils (An & Li, 2020). We also found that nanofibrils maintained the integrity of α‐helix structures, whereas hydrolysates obtained by papain and neutral protease did not form nanofibrils.…”

Amyloidogenesis: What Do We Know So Far?

“…This initial change in the native monomer might even be brought about by chemicals (not necessarily denaturants). For example, proteolysis of a short stretch of polypeptide or glycosylation, changes brought about by pH might alter the aggregation propensity of the protein molecules [192][193][194]. The conformational and/or chemical changes in the native monomer might even be brought about by physical cues, such as pressure, etc.…”

Aggregation and gelation of soy protein : Effects of selective proteolysis and physical modifications

“…These findings suggest that fibrillation processes of ꞵ-conglycinin and glycinin were different and could be mutually affected when these two components coexist in SPI. Apart from our study, only one study so far explored the effects of enzymatic proteolysis on the formation of soy protein fibrils [223]. In that study, the authors used traditional proteolysis and mentioned that the hydrolysate prepared by papain were less favorable for the formation of nanofibrils, but neither microscope images nor the enzymatic conditions were provided [223].…”

“…Apart from our study, only one study so far explored the effects of enzymatic proteolysis on the formation of soy protein fibrils [223]. In that study, the authors used traditional proteolysis and mentioned that the hydrolysate prepared by papain were less favorable for the formation of nanofibrils, but neither microscope images nor the enzymatic conditions were provided [223]. In here, the ability of DβH to form longer and semiflexible fibrils could make it a promising thickening agent or structural ingredients, as these protein fibrils proved to have high viscosity and shear thinning behavior [6].…”