Effect of light intensity and phosphate concentration on the storage and utilization of phosphate in Chlorella vulgaris

This study aims to analyze the effects of light intensity and phosphate concentration on the phosphorus metabolism of microalgae, focusing on the balance between acid soluble phosphate (ASP) and acid insoluble phosphate (AISP). From the changes in the storage and utilization of ASP and AISP under varying light conditions and external phosphorus concentrations, a conceptual model for the intracellular phosphorus metabolism of Chlorella vulgaris was proposed. Changes in photosynthesis and respiration during the utilization of ASP and AISP stored within microalgal cells revealed that higher light intensities led to greater use of ASP in photosynthetic metabolism. The increased utilization of ASP also activated photosynthetic metabolism. In contrast, more AISP was stored at lower light intensities, and the stored AISP was utilized for photosynthesis and ATP production following the depletion of external phosphorus. Furthermore, AISP utilization following external phosphorus depletion was higher under low light conditions, with increased AISP consumption correlating with reduced cellular respiration. These findings indicate that light intensity and external phosphorus concentration significantly influence the storage forms of ASP and AISP in microalgae, thereby affecting their metabolic activity.