The characteristics of biomass production, lipid accumulation and chlorophyll biosynthesis of Chlorella vulgaris under mixotrophic cultivation

The main objective of this study was to investigate the behaviors of Chlorella vulgaris for biomass production, lipid accumulation and chlorophyll biosynthesis under mixotrophic cultivation. The obtained results show that mixotrophism might be a competitive pattern for the culture of C. vulgaris on a large scale based on the achieved maximum biomass and volumetric productivities of lipid and chlorophyll. Glucose was the optimal carbon source for mixotrophic cultivation of C. vulgaris and the effects of glucose content on the alga growth under mixotrophic conditions were considerable because lower glucose content (1 g/l) promoted the production of biomass and photosynthetic pigments; higher glucose contents ( > 5 g/l) increased the biomass and lipid accumulation but inhibited the chlorophyll biosynthesis. The microalga could not grow well without pH control when ammonium and organic nitrogen were the sole nitrogen sources in the mixotrophic cultures because of the remarkable drop in pH value, while the critical urea concentration was observed at 0.50 g/l. It was concluded that mixotrophic cultivation of C. vulgaris is a feasible approach for lipid accumulation and chlorophyll biosynthesis that are dependent on the enhancement of biomass content and volumetric  productivity. Key words: Chlorella vulgaris, mixotrophic cultivation, biomass production, lipid accumulation, chlorophyll biosynthesis.