Gracilariopsis hommersandii, a red seaweed, source of agar and sulfated polysaccharides with unusual structures.

Author

Rodrigo A Rodríguez Sánchez

Affiliation

CONICET-Universidad de Buenos Aires, Centro de Investigación de Hidratos de Carbono (CIHIDECAR), Ciudad Universitaria, Pabellón 2, C1428EGA, Buenos Aires, Argentina; Universidad de Buenos Aires, Facultad de Agronomía, Departamento de Biología Aplicada y Alimentos, Cátedra de Química de Biomoléculas, Av. San Martín 4453, C1417DSE, Buenos Aires, Argentina. Electronic address: [Email]

Abstract

Red seaweed Gracilariopsis hommersandii produces important amounts of non-gelling galactans, which were extracted with hot water (GrC, yield, 37%, viscosity average molecular weight, Mv 109 kDa), comprising agarose and sulfated galactan structures. The alkali modified derivative, GrCTr (Mv 95 kDa), gave a galactose:3,6-anhydrogalactose molar ratio of 1.0:0.9, and a more regular structure, favouring gelation (melting and gelling temperatures 64 and 14 °C, respectively). The rheological properties of this product suggest possible applications as hydrocolloid. G. hommersandii also biosynthesizes non gelling sulfated galactan fractions with diads constituted by β-d-galactose and partially cyclized α-l-galactose units or non-cyclized α-d-galactose residues. Sulfation was mainly detected on C6 or C4 of the β-d-galactose units, and on C6 and, in minor amounts, on C3 of the α-l-galactose units. The presence of β-apiuronic acid was demonstrated for these fractions as side chains of the galactan backbone. Carrageenan structures were found for the first time in an agarophyte of the Gracilariales.

Keywords

Agar,Apiuronic acid,Gracilariopsis hommersandii,Sulfated galactans,d/l-Hybrid galactans,

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