Inhibition of glucose assimilation in Auxenochlorella protothecoides by light
Abstract Background: The yield of microalgae biomass is the key to affect the accumulation of fatty acids. A few of microalgae can assimilate organic carbon to improve biomass yield. In mixotrophic cultivation, organic carbon source and light energy exist simultaneously. The preference of the main energy source by microalgae determines the biomass yield. Auxenochlorella protothecoides is an oleaginous mixotrophic microalga that can efficiently assimilate glucose and accumulate a large amount of biomass and fatty acids. The current study focused on the effect of light on the growth and glucose assimilation of Auxenochlorella protothecoides.Results: In this study, we found that the uptake and metabolism of glucose could be inhibited by light, resulting in a reduction of biomass growth and lipid accumulation. Comparative proteomics of A. protothecoides grown under illumination and in the dark revealed that glucose-3-phosphate (G3P) produced in the dark reaction of photosynthesis could reversibly inhibit the glycolysis pathway and thus glucose metabolism. Moreover, the increase of NADH levels and redox potential of the medium under illumination might inhibit the activity of the glucose transport system and subsequently reduce glucose uptake.Conclusions: The regulatory mechanism by which illumination controls glucose assimilation and biomass accumulation in A. protothecoides was elucidated for the first time, which will facilitate further studies on the complex mechanisms underlying the transition from autotrophy to heterotrophy for improving biomass accumulation.