Fingerprinting and characterization of the polysaccharides from Polygonatum odoratum and the in vitro fermented effects on Lactobacillus johnsonii.

Polygonatum odoratum (Yu-Zhu) can be utilized to treat the digestive and respiratory illness. Previous studies have revealed that the underlying therapeutic mechanism of P. odoratum polysaccharides (POPs) is associated with remodeling the gut microbiota. However, POPs in terms of the chemical composition and fermentation activities have been understudied. Here we developed the three-level fingerprinting approaches to characterize the structures of POPs and probed into the beneficial effects on promoting the growth and fermentation of Lactobacillus johnsonii. POPs were prepared by water decoction followed by alcohol sedimentation, while trifluoroacetic acid under different conditions to prepare the hydrolyzed oligosaccharides and monosaccharides. POPs exhibited three main molecular distribution of 601-620 kDa, 4.12-6.09 kDa, and 3.57-6.02 kDa. Hydrolyzed oligosaccharides with degree of polymerization (DP) 2-13 got primarily characterized by analyzing the rich fragmentation information obtained by hydrophilic interaction chromatography/ion mobility-quadrupole time-of-flight mass spectrometry (HILIC/IM-QTOF-MS). Amongst them, the DP5 oligosaccharide was characterized as 1,6,6-kestopentaose. The molecular ratio of Fru: Ara: Glc: Gal: Xyl was 87.72: 0.30: 11.56: 0.19: 0.23. In vitro fermentation demonstrated that 4.5 mg/mL of POPs could significantly promote the growth of L. johnsonii. Co-cultivated with 4.5 mg/mL of POPs, L. johnsonii exhibited stronger antimicrobial activity against Klebsiella pneumoniae. The concentrations of short-chain fatty acids in the POPs-lactobacilli fermented products, including acetic acid, isobutyric acid, and isovaleric acid, were increased. Conclusively, POPs represent the promising prebiotic candidate to facilitate lactobacilli, which is associated with exerting the health benefits.