Biodiesel production from Chlorella vulgaris under nitrogen starvation in autotrophic, heterotrophic, and mixotrophic cultures

Fatty acid production from Chlorella vulgaris under nitrogen starvation in autotrophic, heterotrophic, and mixotrophic cultures was investigated and compared in this study. Both the biomass and fatty acid productivities of mixotrophic algal cells exceed the combination of autotrophic and heterotrophic cells when acetate was adopted as the organic carbon source, and fatty acid productivity from mixotrophic culture (130 mg L−1 day−1) is 1.9 times greater than the combination of autotrophic (15 mg L−1 day−1) and heterotrophic (51 mg L−1 day−1) cultures. C18:1 is the predominant fatty acid accounting for 60.4 and 64.5% of the total fatty acids in the mixotrophic and heterotrophic cultures, respectively. Moreover, the fatty acid yield from mixotrophic culture is almost two times greater than from heterotrophic culture. Proteomic analysis revealed that the activity of the tricarboxylic acid (TCA) cycle is improved in mixotrophic culture when compared with heterotrophic culture, leading to more fatty acid synthesis in C. vulgaris.