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Towards improving biofuel production - Oil synthesis and accumulation pathways in promising oleaginous microalgae

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Oil production from algae

Microalgae that synthesise oils under stress conditions are a potential new avenue for biofuel production using genetically modified crops. EU researchers studied the genetic and cellular mechanisms behind oil synthesis in such an alga.

Industrial Technologies
Food and Natural Resources

Microscopic algae that photosynthesise are considered a viable and sustainable source of biofuel feedstock because they can produce more biomass per land area than plants. Feedstock is biological material that can be used directly as a fuel or converted to another form of energy. Oleaginous microalgae are microscopic algae that have the potential to produce high levels of oils. One of their key features is that under stressful environmental conditions, they produce substantial amounts of lipids (20-50 % of their dry weight). These lipids are mainly in the form of triacylglycerols, which are valuable fuel precursors. The EU-funded ALGAEOILSYNTH (Towards improving biofuel production - Oil synthesis and accumulation pathways in promising oleaginous microalgae) initiative used cellular, molecular and genetic analyses to understand how oleaginous photosynthetic microalgae produce and accumulate oil in their cells. To do this, the scientists characterised Nannochloropsis oceanica, a unicellular green alga that produces extraordinarily high levels of triacylglycerols when stressed. The genome of this alga includes 13 genes encoding enzymes responsible for triacylglycerol synthesis, called diacylglycerol acyltrasferase (DGAT)-encoding genes. To identify the genes involved in triacylglycerol synthesis under nutrient stress, the scientists grew N. oceanica in nitrogen-deprived and optimal conditions. The expression profiles of the DGAT-encoding genes were compared in the two sets of algae. The results revealed six DGAT-encoding genes involved in triacylglycerol synthesis when N. oceanica is nitrogen-deprived. Differences between the two conditions were particularly strong for one DGAT-encoding gene, which showed a 20-fold increase at its maximum level of expression. The scientists conducted further experiments that reinforced that this gene has potential for the genetic engineering of triacylglycerol synthesis in other organisms. ALGAEOILSYNTH has contributed new knowledge of lipid synthesis in oleaginous microalgae, offering a novel avenue for genetic engineering to boost biofuel production globally. The DGAT-encoding gene identified by this project is a potential tool for future research to enhance the energy density of such transgenic crops.

Keywords

Biofuel, oil synthesis, oleaginous microalgae, ALGAEOILSYNTH, triacylglycerol synthesis

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