Compositional Changes on Freshwater Leaching of the Marine Algae Nereocystis luetkeana and Macrocystis integrifolia

Abstract

An assessment of the chemical components in Nereocystis luetkeana and Macrocystis integrifolia before and after sequential freshwater leaching demonstrated that a high degree of separation of inorganic from organic elements was achieved by freshwater leaching of both algae with a high proportion of the proteinaceous and polysaccharide material being retained. Significant retention in di- and tri-valent cations present as minor and trace elements was observed and the retention of iodine suggested its partial inclusion as a covalently bound element. Even after exhaustive leaching alginate was almost totally retained in both residual algal tissues, essentially as a combined salt of potassium, sodium, and polyvalent ions with the latter imparting a net insoluble nature to the molecule. Fucoidan was the principal polysaccharide leached from both algae and was solely responsible for the mucilaginous nature of chopped Nereocystis and Macrocystis. Potassium, sodium, and chloride ions accounted for the major losses on leaching both algae and could be removed prior to drying and transportation of these plants as sources of alginate salts. The virtual loss of all mannitol and chloride suggested that intracellular constituents were the major leachates while the cell wall components were essentially retained. Commercial implication of these results are considered.Key words: Nereocystis luetkeana, Macrocystis integrifolia, marine algae, inorganic elements, alginate, fucoidan, mannitol, protein, water leaching