Changes in soy protein immunoglobulin E reactivity, protein degradation, and conformation through fermentation with Lactobacillus plantarum strains

This study investigated the fermentation of soy protein isolates (SPI) by using 8 Lactobacillus plantarum strains, its reduction effect on immunoglobulin E (IgE) reactivity, and its relationship with protein degradation and conformation changes. L. plantarum showed potency in reducing IgE reactivity by 83.8%-94.8%, as determined by sandwich enzyme-linked immunosorbent assay. Fermentation resulted in a great reduction (53.8%-92.8%) in soluble protein content and loss of intensity in several major bands, especially those of 7S α', α, and β subunits, as indicated by electrophoresis. Increased peptide (<10 kDa) content was observed in some fermented samples, especially in those fermented by L. plantarum B1-6 and L. plantarum Y-1. Conformation of SPI was altered, as demonstrated by improved surface hydrophobicity (1.6-3.3 times) and emergence of β-strand structure in all fermented samples. Principal component analysis confirmed that peptide (<10 kDa) content, surface hydrophobicity, and β-strand were closely related to IgE reactivity reduction. The reduction of SPI IgE reactivity by L. plantarum was probably attributed to the alternation in primary and higher structure of the protein.