Development of a mixotrophic cultivation strategy for simultaneous improvement of biomass and photosynthetic efficiency in freshwater microalga Scenedesmus obliquus by adding appropriate concentration of sodium acetate

Abstract

To study the biomass and photosynthetic efficiency difference of freshwater microalga Scenedesmus obliquus under autotrophic and mixotrophic cultivation mode, the biomass production, photosynthetic pigments, and photosynthetic efficiency were investigated by lab-scale cultivation experiments. Specifically, S. obliquus was cultured in BG11 medium supplemented with different concentrations of exogenous sodium acetate to examine the physiological and biochemical effects on the oil rich freshwater algae S. obliquus. Results showed that exogenous sodium acetate exerted a “low promotion and high suppression” effect on the biomass production and photosynthetic pigments accumulation, and the biomass production and pigment contents peaked at a sodium acetate concentration of 10.00 mg L−1. Meanwhile, photosynthetic efficiency was significantly increased under low concentration of sodium acetate, however, when adding the high concentrations of sodium acetate, the oxygen evolving complex in donor side of reaction center was damaged, and electron transport at the donor and receptor sides of the reaction center was also suppressed, accompanied by the changes of the absorption, transfer, and application of light energy. These findings provide a strategy to boost biomass accumulation of S. obliquus by mixotrophic cultivation mode with appropriate concentration of sodium acetate, and would be conducive to further accelerate the industrialization of this strain.