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Biologie intégrative du métabolisme lipidique chez les levures du genre Blastobotrys

Abstract : Ascomycetous oleaginous yeasts are among the highest known producers of lipids of our era that may supply lipids compounds, derived chemicals and organic acids from simple or complex carbon sources. We chose oleaginous yeasts species of Blastobotrys genus for defining a new model organism for fatty acid production and lipids, because these oleaginous yeasts natively produce higher lipids rate than Yarrowia lipolytica in the same conditions and can metabolize glucose and xylose. Most of the metabolic engineering studies on these yeast species focused on other molecules compounds than lipids. We characterized the oleaginous traits of two strains belonging to two different species of genus Blastobotrys, using glucose, xylose, glycerol, fructose, cellobiose, sucrose, galactose, starch and oleic acid as substrates with a C/N ratio of 60. We found the higher lipid production (35%) on cellobiose and glucose (32%).Next, in order to further understand the lipid metabolism in Blastobotrys, we explored the effect of temperature on cell physiology, lipid production and lipid profile using YNB medium with 30 g/L glucose. No markedly transition were found from the hyphae to budding form or reversely on YNB medium under four temperatures (28°C, 37°C, 42°C, 45°C). The lipids production is favored at 28°C and C18:1 is the most abundant fatty acid in the lipid profile. We successfully transformed the yeast species B. raffinosifermentans using the Xplor2 system. We increased lipid accumulation by over-expressing two native diacylglycerol acyltransferase genes, DGA1 and DGA2. Our best strain, derived from the parental strain G1212, produced 26.5 g/L lipid from 30g/L glucose in shake-flask experiments. This strain also produced citric acid like Y. lipolytica. We didn’t find significant overall elevated expression in lipid synthesis pathway for DGA1 gene when lipid production was favored on contrary to DGA2 gene. This work represents one of the first metabolic engineering of B. adeninivorans for lipid production.
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Submitted on : Wednesday, May 15, 2019 - 7:09:17 PM
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Daniel Ruben Akiola Sanya. Biologie intégrative du métabolisme lipidique chez les levures du genre Blastobotrys. Biochimie, Biologie Moléculaire. Université Paris Saclay (COmUE), 2019. Français. ⟨NNT : 2019SACLA002⟩. ⟨tel-02130480⟩



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