analysis-of-fatty-acid-content-and-composition-in-microalgae

Analysis of Fatty Acid Content and Composition in Microalgae

A method to determine the content and composition of total fatty acids present in microalgae is described. Fatty acids are a major constituent of ...

Wageningen University and Research Center

Microalgae-derived lipids are an alternative to vegetable and fossil oils, but lipid content and quality vary among microalgae strains. Selection of a suitable strain for lipid production is therefore of paramount importance. Based on published results for 96 species, nine strains were selected to study their biomass, total fatty acid, and triacylglycerol (TAG) production under nitrogen-sufficient and deficient cultivation conditions. Under nitrogen-deficient conditions, Chlorella vulgaris, Chlorella zofingiensis, Neochloris oleoabundans, and Scenedesmus obliquus, accumulated more than 35% of their dry weight as TAGs. Palmitic and oleic acid were the major fatty acids produced. The main difference between these strains was the amount of biomass that was produced (3.0-7.8-fold increase in dry weight) and the duration that the biomass productivity was retained (2-7 days) after nitrogen depletion. S. obliquus (UTEX 393) and C. zofingiensis (UTEX B32) showed the highest average TAG productivity (322 and 243 mg l(-1)day(-1)).

The impact of nitrogen starvation on the dynamics of triacylglycerol accumulation in nine microalgae strains.

Microalgae-derived lipids in the form of triacylglycerols (TAGs) are considered an alternative resource for the production of biofuels and food commodities. Large scale production of microalgal TAGs is currently uneconomical. The cost price could be reduced by improving the areal and volumetric TAG productivity. The economic value could be increased by enhancing the TAG quality. To improve these characteristics, the impact of light intensity, and the combined impact of pH and temperature on TAG accumulation were studied for Scenedesmus obliquus UTEX 393 under nitrogen starved conditions. The maximum TAG content was independent of light intensity, but varied between 18% and 40% of dry weight for different combinations of pH and temperature. The highest yield of fatty acids on light (0.263 g/mol photon) was achieved at the lowest light intensity, pH 7 and 27.5 °C.

Effect of light intensity, pH, and temperature on triacylglycerol (TAG) accumulation induced by nitrogen starvation in Scenedesmus obliquus.

Many microalgae accumulate carbohydrates simultaneously with triacylglycerol (TAG) upon nitrogen starvation, and these products compete for photosynthetic products and metabolites from the central carbon metabolism. As shown for starchless mutants of the non-oleaginous model alga Chlamydomonas reinhardtii, reduced carbohydrate synthesis can enhance TAG production. However, these mutants still have a lower TAG productivity than wild-type oleaginous microalgae. Recently, several starchless mutants of the oleaginous microalga Scenedesmus obliquus were obtained which showed improved TAG content and productivity.

Superior triacylglycerol (TAG) accumulation in starchless mutants of Scenedesmus obliquus: (II) evaluation of TAG yield and productivity in controlled photobioreactors.

Microalgae are often considered as a promising alternative source of vegetable oils. These oils can be used for food and biofuel applications. Productivities that are projected for large-scale microalgal oil production are, however, often poorly supported by scientific evidence and based on too optimistic assumptions. To facilitate the inclusion of the microalgal physiology in these projections, existing knowledge and novel scientific insights were condensed into a mechanistic model that describes photosynthesis and carbon partitioning during nitrogen starvation. The model is validated using experimental data from both wild-type and a starchless mutant of Scenedesmus obliquus. The model is subsequently used to quantify how reactor design, process design, and strain improvement can improve the oil productivity from 2.1 to up to 10.9gm(-2)day(-1). These projected productivities are used to reflect on commonly assumed oil productivities and it is concluded that the microalgal oil productivity is often overestimated several folds.

Article	Year
The impact of nitrogen starvation on the dynamics of triacylglycerol accumulation in nine microalgae strains. Bioresource technology\| PubMed ID: 22995162	2012
Effect of light intensity, pH, and temperature on triacylglycerol (TAG) accumulation induced by nitrogen starvation in Scenedesmus obliquus. Bioresource technology\| PubMed ID: 23774290	2013
Superior triacylglycerol (TAG) accumulation in starchless mutants of Scenedesmus obliquus: (II) evaluation of TAG yield and productivity in controlled photobioreactors. Biotechnology for biofuels\| PubMed ID: 24883102	2014
Opportunities to improve the areal oil productivity of microalgae. Bioresource technology\| PubMed ID: 25836038	2015

Guido Breuer

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