Metabolomic And Network Analysis Of Astaxanthin-producing Mechanism In Haematococcus Pluvialis NIES 144

Astaxanthin exhibits very high antioxidant activity even higher than that of ?-carotene or vitamin E and has valuable application in pharmaceutical, cosmetic andfood industries. A freshwater green microalga Haematococcus pluvialis can synthesize and accumulate significant amount of astaxanthin upon stress conditions, and several stress conditions such as excess acetate, nitrogen limitations, high light, and salt stress were conducted on H. pluvialis.In the study, we evaluated various combinations of acetate(Ac), Fe2+ and high light(HL) stress conditions for their effects on the astaxanthin accumulation and biomass production in H. pluvialis. The results showed that a combination of Fe2+ & HL condition induced more astaxanthin than other stress conditions. We then applied GC-MS and LC-MS based metabolomics to further determine possible mechanisms responsible for the enhancing effects of the stress conditions. With the analytical protocols we optimized, the GC-MS or LC-MS analyses allowed identification of 93 and 24 cellular metabolites from the H. pluvialis cells, respectively. In addition, we constructed a metabolic network using the GC-MS metabolomic datasets by a WGCNA approach. The network analysis uncovered 2, 1 and 1 distinguished metabolic modules highly associated with HL, Fe2+ & HL, and Ac & Fe2+ & HL conditions, respectively. One hub metabolite, D-(+) altrose, was also identified as closely associated with the Fe2+ & HL condition. Finally, LC-MS analysis also showed that GLU, AKG and R5 P were key metabolites positively associated with the Fe2+ & HL condition.The study provided the first metabolomic view of cell growth and astaxanthin accumulation in H. pluvialis, and also demonstrated the effectiveness of the metabolomic and network analysis in identifying key metabolites and metabolic modules related to astaxanthin accumulation in H. pluvialis.