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    Induction of triacylglycerol production in Chlamydomonas reinhardtii: Comparative analysis of different element regimes
    (Elsevier Sci Ltd, 2014) Cakmak, Zeynep E.; Olmez, Tolga T.; Cakmak, Turgay; Menemen, Yusuf; Tekinay, Turgay
    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. Crown Copyright (C) 2013 Published by Elsevier Ltd. All rights reserved.
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    Nitrogen and sulfur deprivation differentiate lipid accumulation targets of Chlamydomonas reinhardtii
    (Landes Bioscience, 2012) Cakmak, Turgay; Angun, Pinar; Ozkan, Alper D.; Cakmak, Zeynep; Olmez, Tolga T.; Tekinay, Turgay
    Nitrogen (N) and sulfur (S) have inter-related and distinct impacts on microalgal metabolism; with N starvation having previously been reported to induce elevated levels of the biodiesel feedstock material triacylglycerol (TAG), while S deprivation is extensively studied for its effects on biohydrogen production in microalgae. 1,2 We have previously demonstrated that N- and S-starved cells of Chlamydomonas reinhardtii display different metabolic trends, suggesting that different response mechanisms exist to compensate for the absence of those two elements. 3 We used C. reinhardtii CC-124 mt(-) and CC-125 mt(+) strains to test possible metabolic changes related to TAG accumulation in response to N and S deprivation, considering that gamete differentiation in this organism is mainly regulated by N. 4 Our findings contribute to the understanding of microalgal response to element deprivation and potential use of element deprivation for biodiesel feedstock production using microalgae, but much remains to be elucidated on the precise contribution of both N and S starvation on microalgal metabolism.