Abstract: The impact of Lactobacillus plantarum on the immunological activity of tropomyosin (TM) as the major shrimp allergen was investigated. TM enriched and purified from Penaeus vanname was hydrolyzed for durations between 12 and 48 h with the viable cells, broken cell contents, cell debris and intracellular enzyme extracts of L. plantarum, the cells from which protein, fat or lipoteichoic acid was removed, and those subjected to carboxyl esterification or aminomethylation, separately. The immunological activity was analyzed by SDS-PAGE, Western-blot and competitive enzyme linked immunosorbent assay (ELISA). In order to analyze the site of action of L. plantarum on TM for reduced immunological activity, epitope polyclonal antibodies combined with infrared spectroscopy was used to explore the influence of L. plantarum on the secondary structure and allergenic epitopes of TM. The immunological analysis results showed that the highest percentage reduction (76.9%) of its immunological activity was obtained when TM was treated with the viable cells for 48 h, and the lowest percentage reduction was observed with the cell debris and the aminomethylated cells (60.7% and 61.7%, respectively), indicating that L. plantarum reduced the immunological activity of TM. The infrared spectroscopy and ELISA results displayed that L. plantarum could greatly change the secondary structure and allergenic epitopes of TM, while the aminomethylated cells and cell debris caused the least damage to the α-helical structure and allergenic epitopes of TM, resulting in less folded structure and thus exerting the worst effect on reducing the immunological activity of TM. Additionally, it was found that amino groups may be an important site of action for L. plantarum to reduce the immunological activity of TM. The findings of this study will provide a theoretical reference to control the allergenicity of food allergens and for the development of hypoallergenic aquatic products.

Key words: Lactobacillus plantarum; tropomyosin; immune activity; reducing effect