PHYTOPLANKTON LIPIDS: INTERSPECIFIC DIFFERENCES AND EFFECTS OF NITRATE, SILICATE AND LIGHT‐DARK CYCLES¹

Abstract

The lipid content of various phytoplankton species was measured in response to nitrogen and silicon limitation and over the cell cycle in synchronized cultures. In a survey of 30 species it was found that during log‐phase growth, green algae contained an average of 17.1% total lipids (% of total dry weight), whereas diatoms contained an average of 24.5%. Nitrogen deprivation for 4 to 9 days resulted in 2‐ to 3‐fold increases in the lipid content of green algae, whereas both increases and decreases were noted in diatoms, depending on the species. The greatest lipid content measured in the study was 72% in Monallantus salina (strain GSB Sticho) which had been deprived of nitrogen for 9 days. Nitrate replenishment in a nitrogen starved culture of Oocystis polymorpha Groover & Bold showed that the excess cellular lipids do not rapidly disappear during recovery, until cell division occurs. A silicate deprivation experiment with Cyclotella cryptica Reimann, Lewin & Guillard (strain 7c) showed an increase in the total cellular lipid fraction from. 30 to 42% of dry weight within 6 h of the onset of silicon limitation, while the mass of lipid material per cell doubled within 12 h. The total lipid fraction in O. polymorpha was found to remain constant over the cell cycle in synchronized cultures regardless of the light regime. The data presented provided the first internally consistent study of phytoplankton lipids for a wide range of species and several growth conditions.

Placing microalgae on the biofuels priority list: a review of the technological challenges

“…Cells accumulate lipids as the growth and division of the cells is put on halt. For example, in the data that Shifrin & Chisholm (1981) presented, there appears to be a trend of a decreasing growth rate with an increase in lipid content. This apparent inverse relationship could have important implications on the economics of algal biofuels.…”

“…The relative composition of algal lipids depends greatly on the species used and the nutrient, environmental and developmental conditions in which the cells are cultured and harvested. For example, it has been shown that the composition of algal lipids varies considerably with the growth cycle, under nutrient limitation and during a diurnal light dark cycle (Shifrin & Chisholm 1981;Cho & Thompson 1986;Sukenik & Carmeli 1990;Ekman et al 2007). It remains to be seen how the composition of the lipids affects the efficiency of biofuel conversion.…”

“…It has been shown that microalgae increase the proportion of triglycerides produced upon nutrient starvation and other environmental stresses, such as temperature and essential nutrients like silicon for diatoms (Shifrin & Chisholm 1981;Roessler 1988Roessler , 1990. Cells accumulate lipids as the growth and division of the cells is put on halt.…”

Microalgal triacylglycerols as feedstocks for biofuel production: perspectives and advances

“…A general trend towards accumulation of lipids, particularly TAG, in response to nitrogen deficiency has been observed in numerous species or strains of various algal taxa, as shown in Figure 1 (Basova, 2005;Beijerinck, 1904;Cobelas and Lechado, 1989;Merzlyak et al, 2007;Roessler, 1990b;Shifrin and Chisholm, 1981;Spoehr and Milner, 1949;Thompson, 1996).…”

The Regulation of Photosynthetic Structure and Function during Nitrogen Deprivation in Chlamydomonas reinhardtii

“…In a range of microalgae, nitrogen (N) deprivation induces high accumulation of starch and TAG (Martin and Goodenough, 1975;Shifrin and Chisholm, 1981;Granum et al, 2002;Hu et al, 2008;Liu and Benning, 2013). In an effort to understand algal TAG production during N deprivation and to guide engineering of higher oil yields, omics-based approaches have been employed (Jamers et al, 2009).…”