Evaluation of probiotic properties of lactic acid bacteria and physicochemical characteristics of fermented jujube (Ziziphus jujuba Mill.) polysaccharides

Microbial fermentation is a novel technology for enhancing the bioactivity of plant polysaccharides. In this study, the probiotic properties of eight strains of lactic acid bacteria (LAB) derived from pickles were evaluated based on their growth performance, cell surface hydrophobicity, and gastrointestinal tolerance. Three strains with superior probiotic characteristics were selected: Lactiplantibacillus pentosus WP2, Lactiplantibacillus plantarum WP5, and Lactiplantibacillus plantarum WP9. The physicochemical properties, structural features, and bioactivity changes of jujube polysaccharides (JCP) fermented by these strains were analyzed. The results demonstrated that the particle sizes of JCP significantly decreased after fermentation by WP2, WP5, and WP9, reducing from 836.02 ± 9 nm (unfermented JCP) to 688.05 ± 3.18 nm, 501.47 ± 4.21 nm, and 634.42 ± 4.21 nm, respectively. The basic structure and glycosidic bond types of JCP remained unchanged during fermentation. However, the fermented polysaccharides (JCP-2, JCP-5, and JCP-9) had higher levels of uronic acid and arabinose in the monosaccharide composition. The mass distribution of high, medium and low molecular weight fractions also changed significantly, with the proportion of low-molecular-weight components increasing from 76.1 % (JCP) to 77.2 %, 83.4 %, and 80.4 %, respectively. The average molecular weights decreased from 0.628 × 10 5  g/mol (JCP) to 0.522 × 10 5  g/mol, 0.555 × 10 5  g/mol, and 0.528 × 10 5  g/mol for JCP-2, JCP-5, and JCP-9, respectively. Scanning electron microscopy (SEM) revealed that the surface structures of JCP-2, JCP-5, and JCP-9 became rougher compared to unfermented JCP. Bioactivity assays indicated that JCP-2 (63.94 % and 74.19 %), JCP-5 (68.68 % and 75.11 %), and JCP-9 (57.85 % and 71.25 %) exhibited superior scavenging activities against DPPH and ABTS radicals compared to unfermented JCP (50 % and 54.5 %). Additionally, the fermented polysaccharides demonstrated enhanced inhibitory activities against α-amylase and α-glucosidase. Fermentation by Lactiplantibacillus pentosus and Lactiplantibacillus plantarum effectively improved the physicochemical properties and bioactivity of jujube polysaccharides, thereby enhancing their processing performance.