Characterization of the alginates from five madagascan brown algae

International audience In this paper, the influence of the conditions of bleaching on initial ground algae is discussed; it is demonstrated that it favours the yield of extraction of purified alginates but that it causes chain degradation and a decrease of the M/G ratio. These events are attributed to the sensitivity to hydrolysis of MM and MG osidic linkages. Nevertheless, from all the results it is shown that four of these original algae (except Sargassum sp. which has a M/G ratio around 1) from Madagascar are rich in guluronic units. Alginates obtained form strong gels in the presence of calcium (1 M CaCl2) with ratios G′/G″ at 1 Hz larger than 6 (up to 8.6). In few cases, it is shown that bleaching favoured gel formation even if the molecular weight is decreased.