Optimizing acid hydrolysis for monosaccharide compositional analysis of Nostoc cf. linckia acidic exopolysaccharide

The exact estimation of monosaccharide composition is important in the primary structure elucidation of polysaccharides. An acid hydrolysis is usually performed for glycosidic bonds cleavage and releasing of mono-saccharides. In this study, optimal conditions of total acid hydrolysis using trifluoroacetic acid (TFA) of acidic lactylated Nostoc cf. linckia exopolysaccharide (EPS) were investigated by NMR spectroscopy. Results of a series of experiments with modified acid concentration, temperature and time of hydrolysis, have shown 2 M TFA, 110 degrees C, 3 h as the most optimal. The stability of EPS monosaccharide components was also explored. Low sta-bility was found at all tested conditions already during the first hour of hydrolysis; all neutral monosaccharides were degraded from 25% to 40% and glucuronic acid to 75%. NMR, contrary to standard techniques used in monosaccharide compositional analysis (HPLC, HPAEC), allowed simultaneous quantification of all GlcA forms; the free one, that one linked in oligosaccharides, as well as GlcA degradation product gamma-lactone. NMR as detection method improves information about uronic acid content in EPS.

Automated summary

The study investigated the optimal conditions for total acid hydrolysis of acidic lactylated Nostoc cf. linckia exopolysaccharide (EPS) using trifluoroacetic acid (TFA). Results showed that 2M TFA, 110 degrees C, 3 hours were the most optimal. The stability of the EPS monosaccharide components was explored, revealing low stability under all tested conditions.