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Thesis
Home   /   Thesis   /   Study of the natural alkane/alkene synthesis pathway in the model microalga Chlamydomonas reinhardtii and genetic engineering of this microalga to produce and excrete these compounds

Study of the natural alkane/alkene synthesis pathway in the model microalga Chlamydomonas reinhardtii and genetic engineering of this microalga to produce and excrete these compounds

Biochemistry Life Sciences Plant biology

Abstract

Microalgae are fast-growing eukaryotic photosynthetic microorganisms that have developed efficient mechanisms to harvest and transform solar energy into energy-rich molecules such as lipids. They are thus potentially great cell factories for production of fuels and biomaterials for the chemical industries. These processes are however still not profitable, mostly because of low oil productivity and high costs of biomass harvest and oil extraction. A major breakthrough would be to create microalgal strains producing and excreting fatty acid-derived hydrocarbons (alkanes and alkenes). Toward this goal, the host team has recently made significant advances: i) Discovery of a novel alka(e)ne-forming enzyme, the photoenzyme fatty acid photodecarboxylase (FAP), which converts free fatty acids to an alka(e)nes, and characterization of the way FAP interacts with its fatty acid substrates at lipid-water interfaces, (ii) Identification of novel players governing the accumulation and turnover of fatty acids in oil reserves (lipid droplets). In this thesis, our goal will be twofold: i) from a fundamental point of view, gain some insights into the way fatty acids are delivered to FAP in the chloroplast as well as into the fate of the hydrocarbon products in the model green microalga Chlamydomonas reinhardtii, ii) from a biotechnological point of view, boost hydrocarbon synthesis and excretion in this microalga. To achieve this goal, specifically, we aim to: i), identify the lipase(s) that is delivering free fatty acids to FAP and determine if any specific proteins bind the hydrocarbon products in membranes, ii) try to boost alka(e)ne synthesis by overexpressing FAP in the cytosol and addressing it to lipid droplets where most of the fatty acids are stored (together with a lipase or as a lipase-FAP chimera), (iii) try to increase hydrocarbon volatility, and thus excretion, by shortening the chain length of the fatty acids without increasing their degradation, (iv) express known hydrocarbon soluble transporters and known ABC transporters at the plasma membrane. This work should therefore contribute to increase our understanding of the detailed mechanism of the generation of alka(e)nes by FAP and of their cellular fate. At a biotechnological level, innovative strategy based on lipid droplets, FAP and hydrocarbons are proposed to build a first version of a eukaryotic photosynthetic cell factory excreting lipids.

Laboratory

Institut de Biosciences et Biotechnologies d’Aix Marseille
Service de Biologie Végétale et de Microbiologie Environnementale
Laboratoire de Bioénergétique et Biotechnologie des Bactéries et Microalgues
Aix-Marseille Université
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