Metabolomic analysis of the effect of nitrogen on fucoxanthin synthesis by the haptophyte Pavlova gyrans

Abstract

Fucoxanthin has a wide range of applications, being used as an additive in functional foods, pharmaceuticals, as well as in cosmetics. The haptophyte Pavlova gyrans OPMS 30543X is a promising fucoxanthin producer owing to its high ability to photosynthetically produce biomass from CO2 and high accumulation of fucoxanthin. A previous study had suggested that NaNO3 is a suitable nitrogen source for Pavlova sp. OPMS 30543, which may be a strain similar to OPMS 30543X, producing fucoxanthin. However, the mechanism by which nitrogen sources affect fucoxanthin production has not been elucidated yet. To develop a nitrogen supplementation strategy for fucoxanthin production, the current study analyzed the effect of nitrogen sources on OPMS 30543X and explored the underlying metabolic phenomena. When supplemented with either NaNO3 or NH4Cl as the sole nitrogen source, the fucoxanthin content of OPMS 30543X cells was 1.7 mg/g- dry cell weight (DCW) higher in NaNO3 medium than in NH4Cl medium. Metabolome analysis revealed that the accumulation of phosphoenolpyruvate (PEP), pyruvate, and 1-deoxy-d-xylulose-5-phosphate (DXP) was not significantly different between the NaNO3 and NH4Cl media. In contrast, accumulation of 2-C-Methyl‑d-erythritol-2,4-cyclopyrophosphate (MEcPP) was higher in the NaNO3 medium than in the NH4Cl medium, suggesting that the downstream process after DXP metabolism could be affected by the nitrogen source. When supplemented with different concentrations of NaNO3, the fucoxanthin content of OPMS 30543X was almost the same across the conditions at the initial stage and decreased in order from the lowest NaNO3 concentration. Metabolomic analysis further revealed that β-carotene and diadinoxanthin levels are lowered after nitrogen depletion. Thus, the nitrogen source and its concentration had different effects on fucoxanthin biosynthesis by OPMS 30543X. The nitrogen supplementation strategy derived from this study, in which OPMS 30543X was cultured with abundant NaNO3, could increase the feasibility of commercial production of fucoxanthin by microalgae.