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Cells Harvesting of Tropic Ocean Oleaginous Microalga Strain Desmodesmus Sp. WC08

Sen Zhang, Ping-huai Liu, Jiang-wei Wu and Qing Wang

For biomass recovery of tropic ocean oleaginous microalgae strain Desmodesmus sp. WC08, eight flocculation methods (pH adjustment, Al2 (SO4)3, polyacrylamide, AlCl3, Ca (OH) 2, FeCl3, alum and chitosan) were evaluated and optimized. The results indicated that ferric chloride, aluminum sulfate, aluminum chloride and chitosan exhibited high flocculation ability and their flocculation efficiency were all beyond 94% at the optimal dosage (0.15, 0.4 and 0.03 gL-1, respectively). Chitosan displayed the most tremendous potential for biomass recovery from culture broth based on its feasibility and safety. Acetic acid and hydrous chloride, used to dissolving chitosan, had no significant difference in the flocculation efficiency. And when the pH of culture broth was set 5 or 6, the flocculation efficiency of chitosan was higher and the required flocculation time was less. More dose chitosan was needed to harvest the biomass following the cell growth stage. Overall, the optimal flocculation reagent for harvesting biomass of Desmodesmus sp. WC08 is chitosan, and its optimal flocculation conditions are: just when the pH of the culture broth was set to 6 and the dosage of chitosan was 0.03 g/L at the end of microalgae cultivation, more than 110g of algal biomass can be recovered just by per 1 g of chitosan. Meanwhile, there is little residual chitosan found in the final flocculation supernatant which can be reused to some extent.