Changes in biomass, photosynthetic efficiency, and total lipid content of Nannochloropsis oculata in response to metabolic intermediates and antioxidant

To study the effects of exogenous metabolic intermediates and antioxidant on Nannochloropsis oculata microalgae strain, the growth performance, biomass productivity, photosynthetic efficiency, and total lipid content were investigated by lab-scale cultivation experiments. Specifically, N. oculata was cultured in f/2 medium supplemented with different concentrations of citric acid or malic acid (0.050, 0.150, 0.750 g L-1) and KI (0.025, 0.050, 0.100, and 0.500 g L-1) to examine the physiological and biochemical effects on the widely distributed marine algae N. oculata. Results showed that the biomass and photosynthetic efficiency showed a downward trend with increasing citric acid and malic acid concentrations, and the low concentrations of metabolic intermediate treatments could enhance the lipid accumulation. The highest lipid content (0.295 or 0.245 g total lipid per gram of dry biomass) was found in cells treated with 0.15 g L-1 of citric acid and malic acid, which was about 28.45% and 6.99% higher than that growing in the culture lacking metabolic intermediates. Compared with malic acid, citric acid had better effect. Furthermore, potassium iodide (KI), an antioxidant, could also boost the lipid content of N. oculata with slight declining biomass productivity, and the highest lipid content (0.300 g total lipid per gram of dry biomass) was found in cells treated with 0.100 g L-1 of KI, which was about 28.08% higher than that growing in the culture lacking KI, indicating that KI may be a potential factor to increase the lipid content of algae cells. These findings not only provide insight into the response mechanism of N. oculata to exogenous metabolic intermediates and antioxidant but also help further broaden the key regulatory factors involved in the lipid accumulation within algal cells.

Automated summary

The effects of citric acid, malic acid, and potassium iodide on N. oculata microalgae were studied. Low concentrations of citric acid and malic acid promoted lipid accumulation, while potassium iodide increased lipid content.