Mixotrophic cultivation of a Chlorella sorokiniana strain for enhanced biomass and lipid production

Because some algae can be grown photoautotrophically, heterotrophically, and/or mixotrophically, they show promise for lipid production as biofuel feedstock with different conditions. In this study, we analyzed microalga Chlorella sorokiniana for biomass and lipid production under three culture modes. The best growth performance was obtained under mixotrophic conditions compared with photoautotrophic and heterotrophic conditions. With the addition of 4 g L−1 glucose, the specific growth rate (3.40 d−1) and maximum biomass dry weight (DW, 3.55 g L−1) in the mixotrophic culture were 1.8- and 2.4-fold of those in the heterotrophic culture, and 5.4- and 5.2-fold of those under the photoautotrophic culture. Most significantly, the biomass yield based on consumed glucose reached values of up to 0.82 g g−1, which was only 0.34 g g−1 in the corresponding heterotrophic condition. Moreover, the lipid content in mixotrophic algae also substantially increased. At a light intensity of 50 μmol m−2 s−1, a lipid content of 45% was achieved compared to only 13% in the heterotrophic culture. The PSII inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) had little effect on the maximum DW and lipid content in the heterotrophic culture, but caused a significant decline in the mixotrophic culture. Mixotrophic cultures supplied with air grew as well as cultures supplied with 1% CO2. Mixotrophy also changed the temperature profiles for growth, increasing the optimum from 25 °C to 37 °C. These results indicate that C. sorokiniana may be an ideal candidate for mixotrophic cultivation that offers great potential in the production of renewable biomass for bioenergy applications.