High pH-induced flocculation of marine Chlorella sp. for biofuel production
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Microalgae are being considered as a promising raw material for biofuel production. However, rapid, efficient, and economic technologies for harvesting microalgae are essential for successful applications. In this study, the high–pH-induced flocculation method was applied to harvest marine Chlorella sp. strains. These algae could be concentrated up to approximately 20-fold by increasing pH using NaOH, with a flocculation efficiency of 90 %. When NaOH dosage was low (1 or 3 mM), the flocculation efficiency decreased considerably with the increase of biomass concentration. At higher NaOH dosage tested (5 or 7 mM), flocculation occurred quickly and efficiently, which tended to be independent of biomass concentration. In larger volumes, all strains were flocculated with similar efficiencies (approximately 90 %) after adding 5 mM NaOH. After flocculation, the flocculated algae cells could be re-cultured as inoculum, and the growth yields in flocculated medium were slightly higher than those from fresh medium. Additionally, for each strain, there were no significant differences in lipid extraction yield and fatty acid composition according to different harvesting methods. These results showed that the high–pH-induced flocculation method could be used to harvest marine Chlorella sp. for biofuel production successfully.
KeywordsFlocculation pH increase Marine microalgae Chlorella sp Lipid extraction Biofuel
This research was supported by the Ocean Public Welfare Scientific Research Project (201305018-3), Funds for Marine Renewable Energy (GHME2011SW04), the Guangdong Ocean Innovative Demonstration Area of Economic Development Project (SZHY2012-B01-003), the Key Research Program of the Chinese Academy of Sciences (KSCX2-EW-B-13), and the Guangdong Ocean Innovative Demonstration Area of Economic Development Project (GD2012-D01-002).