Extraction and Characterization of Alginate from Sargassum angustifolium collected from northern coasts of Persian Gulf, Bushehr

Alginates, unbranched polymers of polysaccharide with gel forming properties made up by blocks of beta-(1-4)-d-mannuronic acid (M) and alpha-(1-4)-l-guluronic acid (G), have emerged as valuable biomaterials with interesting biomedical and biotechnological applications. In brown seaweeds, alginates are the most abundant polysaccharides reaching up to 40% of the dry weight. The extraction of alginate may be regarded as a process in two steps: transformation of insoluble alginate into a soluble form namely sodium alginate, followed by diffusion of the soluble glycuronan into solution.Alginate fractions from Sargassum angustifolium brown seaweed were extracted after collection, washing, drying and grinding of seaweeds into powder, and then characterized by 1HNMR and rheological measurements. 1HNMR spectroscopy is most suitable for characterizing both the composition and the distribution sequence of the two uronate residues in algal samples.The alginate extraction conditions were investigated. In the optimized condition, samples extracted for 3×3h at 50ºC were further purified by re-precipitation with ethanol. The M/G ratio value was 0.89, higher than the ratio for most Sargassum species alginates. The homopolymeric blocks FGG and FMM of these fractions characterized by 1HNMR spectroscopy were 0.39 and 0.33, respectively (η<1). Therefore, the alginate from S. angustifolium is much richer in mannuronic block structures than those from other Sargassum species. Values of Mw for alginate samples were also calculated using intrinsic viscosity data. The Mw value was 702.6 kDa.

کلیدواژه ها:

Alginate ، Sargassum angustifolium ، Mannuronic acid ، Guluronic acid