Random
mutagenesis is an effective strategy for enhancing cellular
traits. In this study, we used the mutagen ethyl methanesulfonate
to create fast-growing Nannochloropsis oculata mutants. When cultivated in a photobioreactor with a diel cycle,
two mutants exhibited 2.2-fold higher carbohydrate productivity and
3.5–4.0-fold higher pigment productivity than the wild type,
while one of them also showed 2.5-fold higher lipid productivity.
A comprehensive physiological, metabolomic, and lipidomic study showed
that the mutants had high levels of glucose-, galactose-, and xylose-based
carbohydrates. Their high growth rate was attributed to increased
chlorophyll a content, improved nitrogen assimilation,
storage, and recycling, and low monogalactosyldiacyl glycerol/digalactosyldiacyl
glycerol ratio, which was responsible for higher biomass productivity.
The investigation revealed upregulation of lipid precursors, shedding
light on high lipid accumulation. The derived algae strains are capable
of increasing the biosynthesis of value-added storage molecules without
impairing growth, rendering them promising candidates for commercial
development in future biorefineries.