The effect of light, salinity, and nitrogen availability on lipid production by Nannochloropsis sp.

Abstract

We examined responses of batch cultures of the marine microalga Nannochloropsis sp. to combined alterations in salinity (13, 27, and 40 g/l NaCl) and light intensity (170 and 700 μmol photons/m(2)·s). Major growth parameters and lipid productivity (based on total fatty acid determination) were determined in nitrogen-replete and nitrogen-depleted cultures of an initial biomass of 0.8 and 1.4 g/l, respectively. On the nitrogen-replete medium, increases in light intensity and salinity increased the cellular content of dry weight and lipids due to enhanced formation of triacylglycerols (TAG). Maximum average productivity of ca. 410 mg TFA/l/d were obtained at 700 μmol photons/m(2)·s and 40 g/l NaCl within 7 days. Under stressful conditions, content of the major LC-PUFA, eicosapentaenoic acid (EPA), was significantly reduced while TAG reached 25% of biomass. In contrast, lower salinity tended to improve major growth parameters, consistent with less variation in EPA contents. Combined higher salinity and light intensity was detrimental to lipid productivity under nitrogen starvation; biomass TFA content, and lipid productivity amounted for only 33% of DW and ca. 200 mg TFA/l/day, respectively. The highest biomass TFA content (ca. 47% DW) and average lipid productivity of ca. 360 mg TFA/l/day were achieved at 13 g/l NaCl and 700 μmol photons/m(2)·s. Our data further support selecting Nannochloropsis as promising microalgae for biodiesel production. Moreover, appropriate cultivation regimes may render Nannochloropsis microalgae to produce simultaneously major valuable components, EPA, and TAG, while sustaining relatively high biomass growth rates.

Effects of cadmium and nitrogen on lipid composition of Chlorella vulgaris (Trebouxiophyceae, Chlorophyta)

“…However, the neutral lipid class TAG did not change significantly in concentration under the combination of Cd/N stress tested here. This differs from the results of Pal et al (2011), who demonstrated that combinations of stress factors can, under certain circumstances, inhibit neutral lipid synthesis in Nannochloropsis sp., while Gardner et al (2011) showed increased TAG production in C. vulgaris under pH stress and N limitation. This means that the response of C. vulgaris, like any other species, can vary under a combination of stress factors.…”

“…The inverse relationship we obtained between TAG and PL has been reported previously and suggested to be due to changes in de novo synthesis of both lipid classes, with modification of their metabolic pathways towards the formation and accumulation of neutral lipids; this occurs via the sequestering of de novo-produced fatty acid moieties in the form of TAG in C. vulgaris (Stephenson et al, 2010) and Nannochloropsis sp. (Pal et al, 2011). Accumulation of TAG under these stress conditions may reflect a preferential use of diacylglycerol for triacylglycerol formation rather than use of phosphatidylcholine (PC) and glycosylglycerides for membrane lipid production.…”

Enhancing Lipid Production of Dunaliella tertiolecta by Manipulating the Interactive Effect of Salinity and Nitrogen

“…The growth of Dunaliella in the absence of nitrogen might be due to the release of internal nitrogen from the cells. 15 The nitrogen uptake was observed in D. tertiolecta with time (Fig. 1b).…”

Growth phase significantly decreases the DHA-to-EPA ratio in marine microalgae

“…For a cost-effective production of nutrient-rich marine microalgae, with high levels of EPA and/or DHA, it is necessary to select highly productive strains while optimizing cultivation conditions. Besides taxon-specific EPA and DHA variability, intracellular LC-PUFA content may be influenced by growth conditions, such as temperature, irradiance and CO 2 concentration (e.g., Jiang and Gao 2004;Pal et al 2011;Boelen et al 2013). During the course of batch growth or when grown under stress, many microalgal species accumulate lipids, especially TAGs (Hu et al 2008).…”