초록
<P>This study proposes a two-stage mixotrophic process for cultivating <I>Chlorella vulgaris</I>. Heterotrophic growth is the dominant step in Phase I (to increase microalgal biomass) and photoautotrophic growth occurs in Phase II (to improve biomass concentration and lipid production). The results show that the addition of the low-cost antioxidant sodium erythorbate (8 g L<SUP>−1</SUP>) significantly accelerates the growth of microalgae in the first stage with air aeration. Furthermore, a higher CO<SUB>2</SUB> fixation rate was obtained in the second stage (at least 344.32 mg CO<SUB>2</SUB> L<SUP>−1</SUP> day<SUP>−1</SUP>) with 10% CO<SUB>2</SUB> aeration. This approximately corresponds to an increase of 177% over simple photoautotrophic cultivation with 10% CO<SUB>2</SUB> aeration during the whole period. The two-stage cultivation strategy achieved a maximum <I>C. vulgaris</I> biomass concentration of 3.45 g L<SUP>−1</SUP> and lipid productivity of 43.70 mg L<SUP>−1</SUP> day<SUP>−1</SUP>, which are 1.85 and 1.64 times those arising due to simple photoautotrophy, respectively. Moreover, an analysis of the product’s fatty acid profile indicates that <I>C. vulgaris</I> might be an ideal candidate for two-stage mixotrophic cultivation of a renewable biomass for use in biodiesel applications. Another interesting point to note from the study is that it is an insufficiency of N and CO<SUB>2</SUB> that probably limits the further growth of <I>C. vulgaris</I>.</P>