Isolation and characterization of a high molecular mass β-glucan from Lactobacillus fermentum Lf2 and evaluation of its immunomodulatory activity

• Published in: Carbohydrate research 2019-04, Vol.476, p.44-52
• Main Authors: Vitlic, Ana, Sadiq, Sohaib, Ahmed, Hafiz I., Ale, Elisa C., Binetti, Ana G., Collett, Andrew, Humpreys, Paul N., Laws, Andrew P.
• Format: Article
• Language: English
• Subjects: beta-Glucans - chemistry; beta-Glucans - isolation & purification; beta-Glucans - pharmacology; Humans; Immunologic Factors - chemistry; Immunologic Factors - isolation & purification; Immunologic Factors - pharmacology; Lactobacillus fermentum - chemistry; Leukocytes, Mononuclear - drug effects; Leukocytes, Mononuclear - immunology; Leukocytes, Mononuclear - metabolism; Lipopolysaccharide Receptors - metabolism; Toll-Like Receptor 2 - metabolism; Tumor Necrosis Factor-alpha - metabolism
• ISSN: 0008-6215; 1873-426X
• DOI: 10.1016/j.carres.2019.03.003

When grown in a semi-defined medium, L. fermentum Lf2 synthesizes significant quantities (∼2 g/L) of two exopolysaccharides (EPS). The two EPS were separated by preparative size exclusion chromatography to give a high molecular mass β-glucan (1.23 × 106 Da) and a medium molecular mass heteroglycan (8.8 × 104 Da). The structure of the high molecular mass β-glucan was determined using a combination of NMR spectroscopy, monomer and linkage analysis. The EPS has the following structure:▪ The immunomodulatory activity of the high molecular mass EPS was studied in peripheral blood mononuclear cells (PBMC). Exposure of PBMC to an aqueous solution of the EPS for 24 h led to increased cell proliferation, changes in expression of the cytokines CD14 and TLR2, and to an increase in production of TNF-α compared to controls. In contrast, when cells that had been treated with EPS for 24 h and from which the EPS had been removed, were subsequently exposed to the bacterial antigen LPS very low levels of TNF-α production were observed. This result indicates that the EPS imparts immunotolerance in PBMC. An ability to modulate the release of the proinflammatory mediators, such as TNF-α, is an important goal in the development of therapies for the treatment of diseases, such as Crohn's disease and ulcerative colitis, associated with excessive release of inflammatory mediators. [Display omitted] •Purification of a high molecular mass exopolysaccharide from L fermentum Lf2.•Characterization of the exopolysaccharide from L fermentum as a β-glucan.•The β-glucan increases the metabolic activity of peripheral mononuclear blood cells.•Exposure of immune cells to β-glucan induces cytokine production.•L fermentum's β-glucan induces immunotolerance in peripheral mononuclear blood cells.