Simultaneous accumulation of neutral lipids and biomass in Nannochloropsis oceanica IMET1 under high light intensity and nitrogen replete conditions

The difficulty in simultaneously obtaining a high production of neutral lipids and biomass in the oleaginous microalga Nannochloropsis is an attractive challenge that needs to be addressed. To overcome this challenge and unveil the underlying metabolic characteristics, the model oleaginous microalga Nannochloropsis oceanica IMET1, under high light intensity and nitrogen-replete conditions, was prepared via steady-state continuous culture in the present study. The simultaneous accumulation of lipids, particularly neutral lipids, and biomass in N. oceanica IMET1 was triggered at a high light intensity (331.2 μmol photons m− 2 s− 1) in the light saturation region accompanied by a sufficient nitrogen supply (2000 μmol L− 1). Moreover, high amounts of valuable fatty acids (arachidonic acid and eicosapentaenoic acid) were also produced. The distribution of fatty acids and intracellular soluble metabolites, the membrane lipid composition and the photosynthetic pathway were associated with the concurrent accumulation of biomass and TAGs in N. oceanica IMET1. The common and different metabolic responses between high-light and nitrogen-depletion strategies for the accumulation of neutral lipids were also discussed. These results provide detailed metabolic clues for the genetic and metabolic engineering of Nannochloropsis for biofuel production.