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C(6)-Oxidation Followed by C(5)-Epimerization of Guar Gum Studied by High Field NMR (Articolo in rivista)

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C(6)-Oxidation Followed by C(5)-Epimerization of Guar Gum Studied by High Field NMR (Articolo in rivista) (literal)

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V. Crescenzi, M. Dentini, D. Risica, S. Spadoni, G. Skjåk-Bræk, D. Capitani, L. Mannina, S. Viel (2004)
C(6)-Oxidation Followed by C(5)-Epimerization of Guar Gum Studied by High Field NMR
in Biomacromolecules
(literal)

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V. Crescenzi, M. Dentini, D. Risica, S. Spadoni, G. Skjåk-Bræk, D. Capitani, L. Mannina, S. Viel (literal)

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Department of Chemistry, University of Rome \"La Sapienza\", Rome, Italy Department of Biotechnology, Norwegian University of Science and Technology, Trondheim, Norway Institute of Chemical Methodologies, CNR, Research Area of Rome, 00016 Monterotondo Staz., Rome, Italy, Department of S.T.A.A.M., University of Molise, 86100 Campobasso, Italy (literal)

Titolo

C(6)-Oxidation Followed by C(5)-Epimerization of Guar Gum Studied by High Field NMR (literal)

Abstract

Guar gum, a â-D-(1f4)-linked D-mannan with R-D-galactopyranosyl units attached as side groups, was treated with R-galactosidase, an enzyme that splits off the R-D-galactosyl units to obtain a galactomannan with a low galactose content. The galactose-depleted polysaccharide was then selectively oxidized in C(6) position and epimerized using mannuronan C(5)-epimerases, namely AlgE1, AlgE4, AlgE6, and their mixtures, obtaining new pseudo-alginates. In this paper, we report a full high field 1D and 2D NMR study of guar gum as such and of the galactose-depleted, oxidized and epimerized compounds, respectively. From the 1H NMR spectra, the degree of epimerization, the distribution of mannuronic acid (M) and guluronic acid (G) residues and the average G-block length, NG>1, were obtained. By means of NMR diffusion experiments, it was also shown that no significant degradation of the polysaccharide occurs as a consequence of the epimerization reactions. (literal)

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