Fermentation of soymilk with Lacticaseibacillus paracasei strain Shirota reduces soluble Gly m 4 levels and allergic reactions associated with soybean-related pollen-food allergy syndrome.

Soybean-related pollen-food allergy syndrome (PFAS) is a food allergy triggered by birch or alder pollen-specific immunoglobulin E, which cross-reacts with soybean proteins homologous to pollen proteins. Although soybean-related PFAS generally causes mild symptoms, some individuals develop severe symptoms, including anaphylaxis, especially after consuming soymilk. This study attempted to reduce the risk of allergy by fermenting soymilk with Lacticaseibacillus paracasei strain Shirota (YIT 9029, LcS). The levels of Gly m 4, which causes soybean-related PFAS, in soymilk and fermented soymilk were analyzed using enzyme-linked immunosorbent assay (ELISA) and western blotting. Reactions to soymilk and fermented soymilk were evaluated in patients with soybean-related PFAS using skin prick tests to compare allergic risks. Gly m 4 levels in the soluble fraction of fermented soymilk were significantly lower than those in soymilk. The reduction in Gly m 4 levels was associated with alterations in the fermentation process, including pH reduction. Additionally, compared with soymilk, fermented soymilk reduced skin prick test reactions in patients with soybean-related PFAS. In conclusion, fermenting soymilk with LcS reduced soluble Gly m 4 levels and alleviated allergic reactions associated with soybean-related PFAS. This study demonstrates the potential of fermented soymilk as a safe and effective alternative for individuals with soybean-related PFAS.