Phosphorus supply via a fed-batch strategy improves lipid heterotrophic production of Chlorella regularis

Intracellular phosphorus (P) accumulation can improve microalgal growth and lipid synthesis. However, large excess of P causes cell poisoning. This study utilized a P-fed-batch strategy to investigate its potential to improve the utilization of the excessive P, while avoiding toxic side effects. This strategy contributed to a more complete utilization of the intracellularly stored P, which enhanced the microalgae biomass by 10−15% by upregulating the brassinosteroid growth hormone gene at a P-fed-batch frequency of 2−8. Furthermore, the lipid content increased by 4−16% via upregulation of lipid synthesis-related genes. As a result, the P-fed-batch strategy significantly increased the lipid production by 13−19%. The content of saturated fatty acid increased by ~ 100%, implying improved combustibility and oxidative stability. This is the first study of this P-fed-batch strategy and provides a new concept for the complete utilization of excessive P.