Production of microalgal biomass and lipids with superior biodiesel-properties by manipulating various trophic modes and simultaneously optimizing key energy sources

Abstract

Two promising oleaginous microalgae, Scenedesmus sp. SPP and marine Chlorella sp. were cultivated under various trophic modes. Both microalgae grew best under mixotrophic/nitrogen-rich mode, indicating good metabolisms of both inorganic (CO2) and organic (glucose) carbon sources. While mixotrophic/nitrogen-starvation conditions promoted the accumulation of lipids with superior biodiesel properties. The key energy sources, including light intensity, CO2 and glucose concentrations, for mixotrophic cultivation of the selected Scenedesmus sp. SPP was simultaneously optimized by Response Surface Methodology. High light intensity combined with high CO2 retarded growth but stimulated lipid/pigment synthesis. Two-stage mixotrophic cultivation using optimal conditions for biomass (light intensity 4.8 klux, CO2 13%, glucose 1% under nitrogen-rich mode) followed by those for lipid accumulation (light intensity 6.0 klux, CO2 15%, glucose 1% under nitrogen-starvation mode) successfully enhanced biomass by 1.46 folds and lipids by 1.39 folds and also improved the biodiesel properties. These strategies may significantly contribute to the development of microalgae-based biofuel and biochemical industries.