Abstract: The aim of this article was to examine the feasibility to cultivate Chlorella protothecoides using waste liquor of Pichia pastoris fermentation and then further optimize the cultivation conditions. The results showed that the P. pastoris fermentation waste liquor had more positive effect on the growth of C. protothecoides than SE culture medium. The highest biomass of 0.65 g/L was achieved after 7 days cultivation when using the fermentation waste liquor diluted to 10 times, which was 2.28 fold of that of SE medium. However, it could not significantly improve the lipid content of C. protothecoides. Then, the culture medium was optimized via single factorial experiments and orthogonal experiments. The obtained optimal culture conditions for the maximum biomass were：0.05 mol/L glucose, 0.01 mol/L NaNO3, 0.003 mol/L KH2PO4, and 300 μL/L seaweed liquid fertilizer. Under the optimal culture conditions, 6.56 g/L dry-weight of C. protothecoides biomass and 33.68% lipid content were achieved. The fatty acid profiles of the lipid were C16：0（25.12%）, C18∶0（4.69%）, C18∶1（50.46%）, C18∶2（6.78%）and C18∶3（8.58%）, which were suitable for biodiesel feedstock.

Key words: Chlorella protothecoides , Fermentation waste liquor of Pichia pastoris , Biomass, Lipid content, Optimization