Identification And Mechanism Analysis Of Chemical Modulators Enhancing Astaxanthin Accumulation In Haematococcus Pluvialis

Photosynthetic microalgae have attracted significant attention as they can serve as important sources for cosmetic, food and pharmaceutical products, industrial materials and even biofuel biodiesels. The carotenoid astaxanthin(3, 3'-dihydroxy-?, ?-carotene-4, 4'-dione) has been found in microalgae, aquatic animals, birds and yeast and is a high-value pigment widely applied in an abroad range of areas due to its high anti-oxidative activity. Haematococcus pluvialis can accumulate up to 5-6%(w/w) of astaxanthin on dry weight basis as a self-defense mechanism under various stresses, thus has become an important natural resource of astaxanthin. In addition to various efforts to improve growth and astaxanthin accumulation, as an alternative approach, chemical modulators, served as metabolic triggers or enhancers that are able to directly adjust cellular metabolism, could be applied in H. pluvialis to improve production or accumulation of astaxanthin.In this study, we evaluated 23 chemicals of 8 groups for their effects on astaxanthin accumulation in H. pluvialis. The results showed that oxidant and signal transduction chemicals increased astaxanthin accumulation in H. pluvialis significantly by more than 20%. To reveal possible regulatory mechanism, a gas chromatography-mass spectrometry(GC-MS) and a liquid chromatography-mass spectrometry(LC-MS) based metabolomic analysis were applied to determine metabolic profiles of H. pluvialis treated with chemical modulators, and then the metabolomic data was analyzed by a partial least squares-discriminate analysis(PLSDA) and a weighted correlation network analysis(WGCNA) to identify possible metabolic modules and metabolites relevant to the increased astaxanthin accumulation. The analyses showed six metabolic modules and six hub metabolites were possibly related to the stimulatory roles of oxidant or signal transduction in H. pluvialis. The study provided new insights to the regulatory mechanisms of oxidant and signal transduction chemicals on astaxanthin accumulation in H. pluvialis.