Lactiplantibacillus plantarum (L. plantarum) and its postbiotics play significant roles in enhancing host immunity, protecting intestinal barrier function and maintaining gut microbiota homeostasis. This study investigated the effects of live L. plantarum and its postbiotics at varying doses on immune system, intestinal barrier integrity and gut microbiota modulation in immunosuppressed mice. Compared to the model control (MC) group, both live and heat-inactivated L. plantarum and its postbiotics significantly enhanced T lymphocyte proliferation and NK cell activity (P < 0.05). They also increased serum cytokine levels (TNF-α, IL-2, IL-4, IL-6, IL-10) and immunoglobulins (IgG and IgM) and upregulated mRNA expression of splenic cytokines (TNF-α, IL-2, IL-6, IL-10). Additionally, they elevated the mRNA expression levels of MyD88, p65, TLR4 and NF-κB in the spleen, thereby activated the TLR4/NF-κB immune signaling pathway. Meanwhile, all treatments significantly upregulated the mRNA expression of tight junction proteins (Claudin-1, Occludin-1 and ZO-1) and mucin (Muc-2), while increasing IgA+ plasma cell numbers in the jejunum (P < 0.05) compared with the MC group. Furthermore, at the phylum level, compared with the MC group, live L. plantarum mixed group (Mix group), low-concentration heat-inactivated L. plantarum mixed group (H-L-Mix group) and the high-concentration heat-inactivated L. plantarum mixed group (H-H-Mix group) all altered the composition of gut microbiota, characterizing by increased the abundance of Firmicutes and decreased the abundance of Proteobacteria. The postbiotic (PB) group showed a significant increase in the abundance of Verrucomicrobia and a decrease in the abundance of Proteobacteria. Compared with the MC group, all treatment groups significantly elevated the concentrations of acetic acid, propionic acid and butyric acid in the gut microbiota of mice (P < 0.05). These results suggested that postbiotics can become a new type of safe dietary supplement, replacing live Lactobacillus to regulate the body's immune activity.

The effects of the amount of magnetic cellulose microcrystalline complex added, oil/water ratio and the number of homogenization cycles on properties of O/W Pickering emulsions stabilized by magnetic cellulose microcrystalline were studied. The results showed that the average size of Fe₃O₄ particles prepared was approximately 10 nm, and the average length of cellulose microcrystals modified by Fe₃O₄ was about 14.2 μm. The surface morphology of cellulose microcrystals was changed from smooth rod to rough morphology. The Fourier transform infrared (FTIR) spectra of cellulose microcrystals showed that the absorption peak of Fe-O bond appeared at 565 cm^-1, and that the contact angles of Fe₃O₄, cellulose microcrystallites and magnetic cellulose microcrystalline complexes were 46.67°, 42.48° and 69.58°, respectively. The optimal conditions for stabilizing Pickering emulsion were determined as follows: addition of 1.5 g/100 mL of magnetic microcrystalline composite, oil/water ratio 3:7 and two homogenization cycles. The initial magnetization value of the magnetic microcrystalline composite was 56.8 emu/g, which was reduced to 4.2 emu/g after fifth repeated use.

The quality of naturally fermented maize flour, unfermented maize flour and maize flour fermented with Lactobacillus plantarum (Lp) and/or Saccharomyces cerevisiae (Sc) was analyzed by using unfermented maize flour as the control.The results showed that the contents of crude protein, crude fat, crude fiber and crude ash in fermented maize flour were significantly lower (P < 0.05) and the content of total starch was significantly higher (P < 0.05) when compared with unfermented maize flour.Fermentation increased the pasting temperature of maize flour significantly (P < 0.05), the breakdown and setback values of naturally fermented and Lp + Sc fermented maize flour were significantly lower than those of unfermented maize flour (P < 0.05), and the stability and anti-retrogradation ability of maize flour were improved.Moreover, fermentation with Lp and Lp + Sc had a pronounced effect on the structure of maize flour, while during fermentation with Sc and Lp + Sc, aroma compounds and metabolites which could improve the off-odor of fermented maize flour were produced.The fermentation periods of maize flour with Lp, Sc and their combination were 72, 18 and 48 hours, respectively compared to 13 days for natural fermentation.Maize flour fermented with Lp + Sc had better quality, flavor and processing properties.