Phagocytosis activity of three sulfated polysaccharides purified from a marine diatom cultured in a semi-continuous system.

An efficient process has been developed for bioactive polysaccharide production and purification from a local diatom isolate, Halamphora sp. AQ4. First, a semi-continuous system with fixed harvesting frequency was employed to cultivate AQ4 for the production of cell mass and polysaccharides for more than 285 days with a high yield of biomass. Six cultivation sets are performed according to different harvesting volumes per 3 days with or without Na2CO3 supplement. The addition of Na2CO3 increases both cell mass and polysaccharide production. Furthermore, three different sulfated polysaccharides (PK1~PK3) were purified from the freshly-grown AQ4 diatoms following anion-exchange chromatography. Among them, polysaccharide PK3 not only has a high content of fucose and uronic acid, but also has a strong activity to stimulate murine macrophage cells and increase their phagocytosis rate up to 170%. This study demonstrates that diatom AQ4 is an important bioresource for the production of bioactive polysaccharides.