Isolation and Characterization of Crude Exopolysaccharides from Different Probiotic Lactic Acid Bacteria and Their Use for Microbial Growth Stimulation

Exopolysaccharides (EPS) from lactic acid bacteria are biological macromolecules with significant biological activities, including functioning as prebiotics to promote the growth of probiotics. This study isolated four lactic acid bacterial strains from kimchi and kefir, namely Lactiplantibacillus plantarum (Lac_KC), Pediococcus acidilactici (Ped_KC), Leuconostoc lactis (Leu_KF), and Weissella cibaria (Wei_KF). Ped_KC and Wei_KF exhibited good abilities to auto-aggregate and co-aggregate with E. coli. Meanwhile, Ped_KC and Lac_KC were more tolerant to simulated gastric and intestinal conditions, while the other two strains exhibited significantly lower survivability under gastric conditions. Regarding the EPS produced from these four strains, the results showed that the recovery from Leu_KF was highest (7.64 g/l). SEM also showed that EPS from Leu_KF had a distinct structure, while FT-IR and XRD showed similarities in their functional groups and amorphous structure. When using EPS as prebiotics, Ped_KC and Leu_KF showed the strongest growth-promoting ability upon EPS addition level of 0.1%.