A mixed white: red light regime leads to enhanced biomass and lipid production in an indigenous phycobiont Trebouxia corticola in a flat panel photobioreactor

Light intensity and quality are critical in determining the production and composition of
microalgal biomass. Response of an indigenous phycobiont Trebouxia corticola to a mixed light-
emitting diodes light regime (White Light 40: Red Light 60) of 450 μmol photons m− 2 s− 1 was
evaluated in a flat panel photobioreactor. The biomass concentration and productivity, specific
growth rate, and carotenoid content were 1.41–2.37 fold, and superoxide dismutase levels were
1.14–1.29 fold higher than white and red light cultures. The maximum photosynthetic efficiency,
photosynthetic electron transport rate, and non-photochemical quenching values were compar­
atively higher than white and red light cultures. The lipid content (35 % w/w), lipid productivity
and the relative eicosapentaenoic acid content of total fatty acid methyl ester were more than
two-fold, four-fold, and 1.28-fold higher than white and red light cultures. A 58.63 % decrease in
carbohydrates, 28 % increase in lipids, significant downregulation of sugar levels, and an upre­
gulation of carboxylic acids compared to white light cultures suggested a diversion of carbon flux
towards lipid biosynthesis. The growth-promoting and oxidative stress-protecting glyoxylate and
dicarboxylic acid metabolic pathways were induced. A substantial expression of the linoleic acid
metabolism pathway suggested that lipid metabolism was significantly influenced. These results
suggest that the mixed light regime used in the present study could effectively influence cellular
metabolism leading to simultaneous production of significantly higher biomass and lipid in
T. corticola. The study suggests that phycobionts like T. corticola could be important candidates for
further studies and strengthens the potential of bioprospecting in identifying microalgae with
desirable traits.