Enhancement of Lipid Productivity and Self-flocculation by Cocultivating Monoraphidium sp. FXY-10 and Heveochlorella sp. Yu Under Mixotrophic Mode

To maintain high microalgae lipid productivity and flocculation efficiency simultaneously and reduce the production cost of microalgae lipids, Monoraphidium sp. FXY-10 with high lipid-producing capacity and Heveochlorella sp. Yu with strong self-flocculation ability were cocultivated and studied. Cocultivated microalgae lipid productivity and flocculation efficiency were increased to 203.8 mg L-1 day(-1) and 70.55%, respectively, which is potentially related to the excessive competitive depletion of nitrogen sources and the upregulation of correlative key genes in lipid anabolic metabolism. Under cocultivation conditions, microalgae cells could enter the stationary phase 2 days earlier than that under monocultivation conditions, thus reducing the culture time. Relative expression of the accD, ME, and rbcL genes was upregulated to varying degrees, and the enzyme activities of ACCase, ME, and RuBisCO were also significantly increased compared with those in monocultivation. Moreover, fatty acid composition showed that microalgae lipids in cocultivation exhibited potential as a feedstock for biodiesel.