Lactylated acidic exopolysaccharide produced by the cyanobacterium Nostoc cf. linckia

• Published in: Carbohydrate polymers 2022-01, Vol.276, p.118801-118801, Article 118801
• Main Authors: Uhliariková, Iveta, Matulová, Mária, Košťálová, Zuzana, Lukavský, Jaromír, Capek, Peter
• Format: Article
• Language: English
• Subjects: Acidic exopolysaccharide; Antioxidant activity; Antioxidants - chemistry; Galactose - chemistry; Glucose - chemistry; Glucuronic Acid - chemistry; Magnetic Resonance Spectroscopy - methods; Molecular Structure; Molecular Weight; Nostoc - chemistry; Nostoc cf. linckia; Nosturonic acid: 3-O-lactyl-β-D-glucuronic acid; Polysaccharides, Bacterial - analysis; Polysaccharides, Bacterial - chemistry; Structure; Xylose - chemistry
• ISSN: 0144-8617; 1879-1344
• DOI: 10.1016/j.carbpol.2021.118801

Cyanobacteria produce a wide range of metabolites of interest for industrial or medical use. The cultivation of freshwater Nostoc cf. linckia yielded 5.4 g/L of a crude exopolysaccharide (cEPS) with a molecular weight of 1.31 × 105 g/mol. Ion-exchange chromatography of cEPS yielded two dominant fractions, EPS-1 and EPS-2, differing in molecular weight. The lower molecular weight fraction (EPS-1) was subjected to structural studies. Results of chemical and spectroscopic analyses showed that three of the four dominant sugars, glucose, galactose and xylose are 1,4-linked in the backbone in the following order: [→4)-β-D-Xylp-(1 → 4)-β-D-Glcp-(1 → 4)-α-D-Galp-(1 → 4)-β-D-Glcp-(1→]n. Terminal mannose residues were identified as side chains linked at C3 of every third backbone xylose and every second glucose is branched at C6 by 3-O-lactyl-β-D-glucuronic acid (nosturonic acid). Antioxidant properties of EPS were tested using two in vitro methods. Both assays showed that the cEPS was more active than purified EPS-1 and EPS-2 fractions and deproteinized EPS.