Lactic acid bacteria fermented soy β-conglycinin: Assessment of structural conformational feature and immunoglobulin E reactivity

Lactic acid bacterial fermentation applies as an emerging strategy for alleviating soy antigenicity. However, the knowledge regarding the underlying relationship between protein structure and immunoreactivity is insufficient. In the present study, β-conglycinin, a major soy allergen, was isolated, and the effect of Lactiplantibacillus plantarum B1-6 fermentation on its structure and immunoreactivity was investigated. The results demonstrated that the immunoreactivity and conformational structures of β-conglycinin were regulated by varied fermentation terminal pH (FT-pH) levels (6.0, 4.5, 4.0, and 3.5) and different β-conglycinin concentrations (0.1%, 0.5%, 1%, and 2%, w/v). The most significant reduction in soy immunoreactivity, which was assayed using a sandwich enzyme-linked immunosorbent assay kit test and the serum of soybean allergy patients, was observed at FT-pH 4.5 regardless of β-conglycinin concentration. The conformational study demonstrated that the loss of the α-helix structure, opening of the tertiary structure, and the formation of aggregates (0.1%–1%, w/v) or gel network (2%, w/v) contributed to the loss of immunoreactivity. Among the four selected concentrations, 2% β-conglycinin (w/v) demonstrated the lowest band intensity in β-subunit, the highest surface hydrophobicity, and the lowest immunoreactivity. Principal component analysis confirmed that fermentation induced changes in protein particle size, intrinsic fluorescence intensity, and hydrogen bond, which were closely related to the immunoreactivity reduction of β-conglycinin.