Microalgae cultivation with high lipid productivity has received much attention in recent years owing to the economic potential of biofuels production and CO2 emission reduction. Previous studies had reported that the ways of pH-regulation, nutrition-limitation and semi-continuous culture mode can either increase the cells growth rate or promote lipid accumulation. In this study, the novel culture strategy of integrating both nutrition limitation and pH-regulation by CO2 in a semi-continuous cultivation was investigated for enhancing the lipid productivity. In the batch culture, the best growth performance was achieved by controlling pH at 7; lipid contents of the cells can be increased under the nitrogen-limitation conditions. The maximum lipid productivity of 115 mg L-1 d(-1) was achieved in the novel culture strategy of semi-continuous cultivation with nitrogen-limitation and pH-regulation by CO2, which was 3.64-fold higher than that in the batch culture without pH control and nitrogen limitation. (C) 2013 Elsevier Ltd. All rights reserved.