Time-series lipidomic analysis of the oleaginous green microalga species Ettlia oleoabundans under nutrient stress

Abstract

BackgroundMicroalgae are uniquely advantageous organisms cultured and harvested for several value-added biochemicals. A majority of these compounds are lipid-based, such as triacylglycerols (TAGs), which can be used for biofuel production, and their accumulation is most affected under nutrient stress conditions. As such, the balance between cellular homeostasis and lipid metabolism becomes more intricate to achieve efficiency in bioproduct synthesis. Lipidomics studies in microalgae are of great importance as biochemical diversity also plays a major role in lipid regulation among oleaginous species.MethodsThe aim of this study was to analyze time-series changes in lipid families produced by microalga under different nutrient conditions and growth phases to gain comprehensive information at the cellular level. For this purpose, we worked with a highly adaptable, oleaginous, non-model green microalga species, Ettlia oleoabundans (a.k.a. Neochloris oleoabundans). Using a mass spectrometry-based untargeted and targeted metabolomics’ approach, we analyzed the changes in major lipid families under both replete and deplete nitrogen and phosphorus conditions at four different time points covering exponential and stationary growth phases.ResultsComprehensive analysis of the lipid metabolism highlighted the accumulation of TAGs, which can be utilized for the production of biodiesel via transesterification, and depletion of chlorophylls and certain structural lipids required for photosynthesis, under nutrient deprived conditions. We also found a correlation between the depletion of digalactosyldiacylglycerols (DGDGs) and sulfoquinovosyldiacylglycerols (SQDGs) under nutrient deprivation.ConclusionsHigh accumulation of TAGs under nutrient limitation as well as a depletion of other lipids of interest such as phosphatidylglycerols (PGs), DGDGs, SQDGs, and chlorophylls seem to be interconnected and related to the microalgal photosynthetic efficiency. Overall, our results provided key biochemical information on the lipid regulation and physiology of a non-model green microalga, along with optimization potential for biodiesel and other value-added product synthesis.Electronic supplementary materialThe online version of this article (10.1186/s13068-018-1026-y) contains supplementary material, which is available to authorized users.

Surviving Starvation: Proteomic and Lipidomic Profiling of Nutrient Deprivation in the Smallest Known Free-Living Eukaryote

“…These changes were accompanied by an increased abundance of betaine lipids ( Table S3 ), which are major membrane components in algae. The presence of DGTA lipid diacylglyceryl-hydroxy-methyl- N , N , N -trimethyl-β-alanine (DGTA) has previously been reported to be the exclusive betaine lipid in O. tauri [ 30 ]. As a result, in this study, betaine lipids have been nominally assigned as DGTA.…”

“…[25,26], Nannochloropsis sp. [27], Chlamydomonas reinhardtii [28], Phaeodactylum tricornutum [29], Ettlia oleoabundans [30], Emiliania huxleyi [31] and O. tauri. [32].…”

Engineering the metabolic pathways of lipid biosynthesis to develop robust microalgal strains for biodiesel production

“…It was also found that mainly they are part of phospholipids and neutral lipids such as triacylglycerols . Lipidomic analysis of Neochloris oleoabundans discovered that TAG accumulation under nitrogen depletion is related to lower production of di‐galactosyl,di‐acylglycerols, phosphatidylglycerols, and chlorophylls . Similarly, 60 triglycerols along with polar lipids have been reported for Scenedesmus sp.…”

Characterization and optimization of endogenous lipid accumulation in Chlorella vulgaris SDEC-3M ability to rapidly accumulate lipid for reversing nightly lipid loss

“…The most feasible strategy to overcome this bottleneck is two-stage strategy, with a biomass production stage under suitable growth conditions, followed by a lipid accumulation stage under stress conditions [1, 16–19]. As the most common stress conditions used in the two-stage strategy [1, 20], N-deficiency caused by a medium excluding nitrogen or containing little nitrogen [12, 14, 19, 21] can induce cellular carbon flux is changed to lipid synthesis instead of carbohydrate and proteins [22], which drastically increases the lipid content in microalgae. It is hypothesized that induction by stress conditions accompanies with night, when the growth of microalgae is always ceased, can minimize, and even reverse the negative effect of nighttime on the lipid accumulation.…”

“…Thus, the feasibility of nightly endogenous lipid accumulation should be confirmed. Second, for most of the microalgae species, the obvious effects of lipid accumulation were usually observed within 2–6 days [21, 23]. For coordinating with light/dark cycle, however, noticeable endogenous lipid accumulation should occur just during about 12-h darkness.…”