Improving lipid productivity by engineering a control-knob gene in the oleaginous microalga Nannochloropsis oceanica

Microalgae are currently considered to be a promising feedstock for biodiesel production. However, significant research efforts are crucial to improve the current biomass and lipid productivities under real outdoor production conditions. In this context, batch, continuous and semi-continuous operation regimes were compared during the Spring/Summer seasons in 2.6 m3 tubular photobioreactors to select the most suitable one for the production of the oleaginous microalga Nannochloropsis oceanica. Results obtained revealed that N. oceanica grown using the semi-continuous and continuous operation regimes enabled a 1.5-fold increase in biomass volumetric productivity compared to that cultivated in batch. The lipid productivity was 1.7-fold higher under semi-continuous cultivation than that under a batch operation regime. On the other hand, the semi-continuous and continuous operation regimes spent nearly the double amount of water compared to that of the batch regime. Interestingly, the biochemical profile of produced biomass using the different operation regimes was not affected regarding the contents of proteins, lipids and fatty acids. Overall, these results show that the semi-continuous operation regime is more suitable for the outdoor production of N. oceanica, significantly improving the biomass and lipid productivities at large-scale, which is a crucial factor for biodiesel production.

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Metabolic response of Botryococcus braunii to high bicarbonate dosages and other conditions: analysis of photosynthetic performance, productivity, and lipidomic profile

Journal of Applied Phycology ◽

10.1007/s10811-021-02544-7 ◽

2021 ◽

Author(s):

Néstor David Giraldo ◽

Sandra Marcela Correa ◽

Andrés Arbeláez ◽

Felix L. Figueroa ◽

Rigoberto Ríos-Estepa ◽

...

Keyword(s):

Nutrient Limitation ◽

Metabolic Response ◽

Neutral Lipids ◽

Biomass Productivity ◽

Botryococcus Braunii ◽

Photosynthetic Performance ◽

Lipid Productivity ◽

Cellular Growth ◽

Adaptive Responses ◽

Nitrogen And Phosphorus

AbstractIn this study the metabolic responses of Botryococcus braunii were analyzed upon different inorganic carbon dosages and nutrient limitation conditions in terms of lipid and biomass productivity, as well as photosynthetic performance. The nutritional schemes evaluated included different levels of sodium bicarbonate and nitrogen and phosphorus starvation, which were contrasted against standard cultures fed with CO2. Bicarbonate was found to be an advantageous carbon source since high dosages caused a significant increase in biomass and lipid productivity, in addition to an enhanced photosynthetic quantum yield and neutral lipids abundance. This contrasts to the commonly used approach of microalgae nutrient limitation, which leads to high lipid accumulation at the expense of impaired cellular growth, causing a decline in overall lipid productivity. The lipidome analysis served to hypothesize about the influence of the nutritional context on B. braunii structural and storage lipid metabolism, besides the adaptive responses exhibited by cells that underwent nutrient stress.

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High-throughput insertional mutagenesis reveals novel targets for enhancing lipid accumulation in Nannochloropsis oceanica

Metabolic Engineering ◽

10.1016/j.ymben.2021.04.012 ◽

2021 ◽

Author(s):

Christian Südfeld ◽

Michal Hubáček ◽

Daniel Rodrigues Figueiredo ◽

Mihris I.S. Naduthodi ◽

John van der Oost ◽

...

Keyword(s):

High Throughput ◽

Lipid Accumulation ◽

Insertional Mutagenesis ◽

Nannochloropsis Oceanica ◽

Novel Targets

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Microalgae as Sustainable Bio-Factories of Healthy Lipids: Evaluating Fatty Acid Content and Antioxidant Activity

Marine Drugs ◽

10.3390/md19070357 ◽

2021 ◽

Vol 19 (7) ◽

pp. 357

Author(s):

Tiago A. Conde ◽

Bruna F. Neves ◽

Daniela Couto ◽

Tânia Melo ◽

Bruno Neves ◽

...

Keyword(s):

Antioxidant Activity ◽

Antioxidant Activities ◽

Fatty Acid Content ◽

Scenedesmus Obliquus ◽

Food Sources ◽

Gas Chromatography Mass Spectrometry ◽

Nannochloropsis Oceanica ◽

Omega 3 ◽

Bioactive Lipids ◽

Food Ingredients

The demand for sustainable and environmentally friendly food sources and food ingredients is increasing, and microalgae are promoted as a sustainable source of essential and bioactive lipids, with high levels of omega-3 fatty acids (ω-3 FA), comparable to those of fish. However, most FA screening studies on algae are scattered or use different methodologies, preventing a true comparison of its content between microalgae. In this work, we used gas-chromatography mass-spectrometry (GC-MS) to characterize the FA profile of seven different commercial microalgae with biotechnological applications (Chlorella vulgaris, Chlorococcum amblystomatis, Scenedesmus obliquus, Tetraselmis chui, Phaeodactylum tricornutum, Spirulina sp., and Nannochloropsis oceanica). Screening for antioxidant activity was also performed to understand the relationship between FA profile and bioactivity. Microalgae exhibited specific FA profiles with a different composition, namely in the ω-3 FA profile, but with species of the same phylum showing similar tendencies. The different lipid extracts showed similar antioxidant activities, but with a low activity of the extracts of Nannochloropsis oceanica. Overall, this study provides a direct comparison of FA profiles between microalgae species, supporting the role of these species as alternative, sustainable, and healthy sources of essential lipids.

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Correction to: Cell wall and organelle modifications during nitrogen starvation in Nannochloropsis oceanica F&M-M24

Journal of Applied Phycology ◽

10.1007/s10811-021-02502-3 ◽

2021 ◽

Author(s):

Bianca Roncaglia ◽

Alessio Papini ◽

Graziella Chini Zittelli ◽

Liliana Rodolfi ◽

Mario R. Tredici

Keyword(s):

Cell Wall ◽

Nitrogen Starvation ◽

Nannochloropsis Oceanica

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Cell wall and organelle modifications during nitrogen starvation in Nannochloropsis oceanica F&M-M24

Journal of Applied Phycology ◽

10.1007/s10811-021-02416-0 ◽

2021 ◽

Author(s):

Roncaglia Bianca ◽

Papini Alessio ◽

Chini Zittelli Graziella ◽

Rodolfi Liliana ◽

Mario R. Tredici

Keyword(s):

Cell Wall ◽

Wall Thickness ◽

Lipid Droplets ◽

Nitrogen Starvation ◽

Photosynthetic Apparatus ◽

Ultrastructural Changes ◽

Total Biomass ◽

Nannochloropsis Oceanica ◽

Final Phase ◽

Cell Functions

AbstractNannochloropsis oceanica F&M-M24 is able to increase its lipid content during nitrogen starvation to more than 50% of the total biomass. We investigated the ultrastructural changes and the variation in the content of main cell biomolecules that accompany the final phase of lipid accumulation. Nitrogen starvation induced a first phase of thylakoid disruption followed by chloroplast macroautophagy and formation of lipid droplets. During this phase, the total amount of proteins decreased by one-third, while carbohydrates decreased by 12–13%, suggesting that lipid droplets were formed by remodelling of chloroplast membranes and synthesis of fatty acids from carbohydrates and amino acids. The change in mitochondrial ultrastructure suggests also that these organelles were involved in the process. The cell wall increased its thickness and changed its structure during starvation, indicating that a disruption process could be partially affected by the increase in wall thickness for biomolecules recovery from starved cells. The wall thickness in strain F&M-M24 was much lower than that observed in other strains of N. oceanica, showing a possible advantage of this strain for the purpose of biomolecules extraction. The modifications following starvation were interpreted as a response to reduction of availability of a key nutrient (nitrogen). The result is a prolonged survival in quiescence until an improvement of the environmental conditions (nutrient availability) allows the rebuilding of the photosynthetic apparatus and the full recovery of cell functions.

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