초록
<P><B>Abstract</B></P> <P>Carbon dioxide (CO<SUB>2</SUB>) and pH are two interdependent factors that greatly impact the growth and lipid accumulation of microalgae. However, the effects of these two factors are usually studied separately. The use of exogenous CO<SUB>2</SUB>, such as flue gas derived, to regulate pH in the large-scale cultivation of microalgae provides an ideal means for combining CO<SUB>2</SUB> biofixation and biodiesel production. In this study, the CO<SUB>2</SUB> biofixation and lipid production of oleaginous microalga <I>Graesiella</I> sp. WBG­1 was explored for four pH levels regulated by exogenous 15% CO<SUB>2</SUB> (flue gas concentration) in 10L circular culture ponds and 5m<SUP>2</SUP> open raceway reactors. Results revealed that pH8.0–9.0 was the optimum pH for CO<SUB>2</SUB> fixation and lipid production, attaining the highest CO<SUB>2</SUB> fixation rates of 0.26gL<SUP>−1</SUP> day<SUP>−1</SUP> and 18.9gm<SUP>−2</SUP> day<SUP>−1</SUP>, respectively, lipid contents of 46.28% and 32.38%, and lipid productivities of 64.8mgL<SUP>−1</SUP> day<SUP>−1</SUP> and 3.14gm<SUP>−2</SUP> day<SUP>−1</SUP>. A positive correlation between CO<SUB>2</SUB> utilization efficiency and pH in open reactors was also suggested in this research, and thus provides direction for screening of CO<SUB>2</SUB> fixation by microalgae. The present study provides an excellent strategy for coupling CO<SUB>2</SUB> fixation and lipid production via microalgae in large-scale cultivation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The lipid production of WBG1 under 4 CO<SUB>2</SUB>-regulated pH levels was evaluated. </LI> <LI> The culture has a maximum CO<SUB>2</SUB> fixation rate under pH8.0–9.0. </LI> <LI> Highest biomass, lipid content and productivity were obtained under pH8.0–9.0. </LI> <LI> There is a positive correlation between CO<SUB>2</SUB> utilization efficiencies and pH values. </LI> <LI> Provide a strategy for coupling and maximizing the CO<SUB>2</SUB> fixation and lipid production. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>