Azide improves triglyceride yield in microalgae

Many species of microalgae accumulate under growth-limiting conditions, such as nitrogen deprivation, large amounts of triglycerides (TAG). The regulation of this process is not clear. Here we demonstrate that sodium azide (Az) induces synthesis of high levels of TAG in the lipid-accumulating marine species Chlorella desiccata. In comparison to N deprivation, Az leads to only minor growth retardation and to smaller inhibition of photosynthesis and respiration, resulting in a 60–80% increase in TAG yield. Maximal TAG induction level by Az is strictly dependent on light intensity and requires high CO2. The cell morphology, TAG level and composition are similar in both treatments. From 17 tested microalgae species, 15 were responsive to Az under different culturing conditions. The results suggest that the higher TAG yield in Az-treated compared to N-deprived cultures, results from the better metabolic state and higher photosynthetic activity of the culture. The potential of Az to improve TAG yield production from microalgae is discussed.