Structural characterization of an exopolysaccharide produced by two strains of Lacticaseibacilluscasei

• Published in: Carbohydrate research 2024-03, Vol.537, p.109056-109056, Article 109056
• Main Authors: Van Calsteren, Marie-Rose, Gagnon, Fleur, Guertin, Nancy, Roy, Denis
• Format: Article
• Language: English
• Subjects: Carbohydrate Sequence; Hexasaccharide repeating unit; High-resolution NMR spectroscopy; Lacticaseibacillus casei strain RW-3703M; Lacticaseibacillus casei strain type V; Magnetic Resonance Spectroscopy; Polysaccharide; Polysaccharides, Bacterial - chemistry; Structure determination
• ISSN: 0008-6215; 1873-426X
• DOI: 10.1016/j.carres.2024.109056

Exopolysaccharides (EPSs) were isolated and purified from Lacticaseibacillus casei strains type V and RW-3703M grown under various fermentation conditions (carbon source, incubation temperature, and duration). Identical 1H NMR spectra were obtained in all cases. The molar mass determined by size-exclusion chromatography coupled with multi-angle light scattering was different for the two strains and in different culture media. The primary structure was elucidated using chemical and spectroscopic techniques. Monosaccharide and absolute configuration analyses gave the following composition: d-Glc, 1; d-Gal, 2; l-Rha, 2; d-GlcNAc, 1. Methylation analysis indicated the presence of 4-linked Glc, terminal and 6-linked Gal, terminal and 3-linked Rha, and 3,4,6-linked GlcNAc. On the basis of one- and two-dimensional 1H and 13C NMR data, the structure of the EPS was consistent with the following hexasaccharide repeating unit: {4)[Rhap(α1-3)][Galp(α1-6)]GlcpNAc(β1-6)Galp(α1-3)Rhap(β1-4)Glcp(β1-}n. Complete 1H and 13C NMR assignments are reported. [Display omitted] •Lacticaseibacillus casei type V and RW-3703M produce the same exopolysaccharide.•Glucose, galactose, rhamnose, and N-acetylglucosamine are the only components.•The structure consists of a hexasaccharide repeating unit.•Two monosaccharide side chains are attached to the backbone GlcNAc residue.