Pulsed electric field (PEF) is an effective way to modulate the structure and activity of enzymes; however, the dynamic changes in enzyme structure during this process, especially the intermediate state, remain unclear. In this study, the molten globule (MG) state of α-amylase under PEF processing was investigated using intrinsic fluorescence, surface hydrophobicity, circular dichroism, etc. Meanwhile, the influence of coexisting carrageenan on the structural transition of α-amylase during PEF processing was evaluated. When the electric field strength was 20 kV/cm, α-amylase showed the unique characteristics of an MG state, which retained the secondary structure, changed the tertiary structure, and increased surface hydrophobicity (from 240 to 640). The addition of carrageenan effectively protected the enzyme activity of α-amylase during PEF treatment. When the mixed ratio of α-amylase to carrageenan was 10:1, they formed electrostatic complexes with a size of ~20 nm, and carrageenan inhibited the increase in surface hydrophobicity (<600) and aggregation (<40 nm) of α-amylase after five cycles of PEF treatment. This work clarifies the influence of co-existing polysaccharides on the intermediate state of proteins during PEF treatment and provides a strategy to modulate protein structure by adding polysaccharides during food processing.

Infectious enteritis caused by bacterial pathogens are a significant global health concern, with high incidence and mortalities worldwide. The objective of this research was to explore the benefits of Lactiplantibacillus plantarum CCNH185 against Citrobacter rodentium-induced colitis in mice. Female C57BL/6J mice (n = 8 per group) were orally administered L. plantarum CCNH185 at a dose of 2 × 10⁹ CFU daily for 24 days, followed by a single oral challenge with C. rodentium (2 × 10⁹ CFU) on day 21. L. plantarum CCNH185 significantly alleviated disease symptoms including body weight loss, colon shortening and histopathological damage (p < 0.05). Treatment with L. plantarum CCNH185 also reduced pro-inflammatory cytokine levels, such as IL-1β and IL-6 (p < 0.05), while increasing anti-inflammatory IL-10 expression (p < 0.05) in the colon. Histological and immunofluorescence demonstrated that L. plantarum CCNH185 improved the intestinal barrier integrity by increasing goblet cell numbers, upregulating MUC2 expression, reducing crypt hyperplasia, and suppressing epithelial cell apoptosis. Furthermore, transcriptomic analysis revealed that L. plantarum CCNH185 suppressed excessive immune cell infiltration and inflammatory responses in the colon during C. rodentium infection. Flow cytometry analysis further confirmed that L. plantarum CCNH185 suppressed hyperactivation of innate immune cells including macrophages, dendritic cells, neutrophils to alleviate inflammation. Furthermore, L. plantarum CCNH185 reshaped the gut microbiota by increasing the abundance of beneficial genera such as Lactobacillus, Dubosiella, and Romboutsia. Correlation analysis linked these microbial shifts with improved inflammatory and apoptotic markers. These findings highlight L. plantarum CCNH185 may serve as a promising preventive probiotic candidate for ameliorating infectious colitis possibly through strengthening the gut mucus barrier, modulating immune responses, and altering gut microbiota composition.