In this study, the influences of oxygen supply and nitrogen starvation on cell growth and lipid production by heterotrophic culture of Chlorella protothecoides were investigated in a 5-L stirred-tank bioreactor. The results demonstrated that both a low oxygen supply and nitrogen starvation are favorable for lipid accumulation, but limit cell growth and may therefore reduce the overall lipid production. Hence, a novel two-stage strategy for oxygen supply and nitrogen starvation was proposed in a batch culture, increasing the lipid content and yield on glucose by a factor 2.14 and 2.03 compared to the one-stage batch culture with high oxygen supply and sufficient nitrogen availability, respectively. Applying the two-stage process in a fed-batch culture further increased the lipid productivity to 175.2 mg/(L.h), giving a lipid yield of 195.6 mg/g. Furthermore, a dual-mode culture, coupling a heterotrophic process with autotrophic process, was implemented to allow for CO2 recycling. This improved the lipid productivity and carbon utilization efficiency, further contributing towards cost-effective and environment-friendly algal lipid production. (C) 2016 Elsevier Ltd. All rights reserved.