Hyper-production of astaxanthin from Haematococcus pluvialis by a highly efficient nitrogen feeding strategy accompanied with high light induction

Haematococcus pluvialis has been used for commercial production of natural astaxanthin, yet the production cost is quite high due to the relatively low production efficiency. Exploring highly efficient cultivation strategies can be used to enhance the economic feasibility. In this study, an efficient nitrogen feeding strategy accompanied with high light induction was explored to enhance the biomass concentration and astaxanthin content in H. pluvialis QLD. The results demonstrated that 1 x NaNO3 was the best feeding source under high light conditions, and feeding two times (Fed-batch II) obtained the best astaxanthin productivity. The maximum values of astaxanthin content, production, and productivity were 65.62 mg/g, 430.29 mg/L, and 26.77 mg/L/d, respectively, under Fed-batch II, surpassing previous findings reported in most studies. Biochemical composition analysis revealed alterations in the biosynthesis of cellular metabolites under Fed-batch II, indicating the mitigation of stresses on microalgal cells and an enhancement of metabolic flux towards astaxanthin production. Moreover, gene expression analysis demonstrated an upregulation of astaxanthin biosynthesis during the late stage of Fed-batch II. The findings elucidate that the proposed fed-batch strategy can be employed for the highly efficient production of natural astaxanthin by H. pluvialis.