Induction of triacylglycerol production in Chlamydomonas reinhardtii: Comparative analysis of different element regimes

• All element regimes, except S deprivation, were associated with decrease in total biovolume.
• Macro- and microelement composition of C. reinhardtii greatly differed.
• Overall TAG output under N, Mg, S or P deprivation was most pronounced.
• FAME profiles of N, S and P deprived cells reflect the requirements of EN 14214.
• Dramatic morphological changes were observed under different element regimes.

In this study, impacts of different element absence (nitrogen, sulfur, phosphorus and magnesium) and supplementation (nitrogen and zinc) on element uptake and triacylglycerol production was followed in wild type Chlamydomonas reinhardtii CC-124 strain. Macro- and microelement composition of C. reinhardtii greatly differed under element regimes studied. In particular, heavy metal quotas of the microalgae increased strikingly under zinc supplementation. Growth was suppressed, cell biovolume, carbohydrate, total neutral lipid and triacylglycerol levels increased when microalgae were incubated under these element regimes. Most of the intracellular space was occupied by lipid bodies under all nutrient starvations, as observed by confocal microscopy and transmission electron micrographs. Results suggest that sulfur, magnesium and phosphorus deprivations are superior to nitrogen deprivation for the induction triacylglycerol production in C. reinhardtii. On the other hand, FAME profiles of the nitrogen, sulfur and phosphorus deprived cells were found to meet the requirements of international standards for biodiesel.