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Modélisation de la bascule métabolique chez les cellules eucaryotes : application à la production de citrate chez la levure Yarrowia lipolytica

Abstract : The main goal of this thesis project is to study and characterize mechanisms involved in respiratory to fermentative shift in eukaryotic cells endowed with mitochondrial metabolism. Eukaryotic cells have different oxygen requirements for energy production and survival in a given environment. They are described as strict aerobic when the presence of oxygen is necessary or optional aero-anaerobic in when oxygen is not essential for energy production. The yeast Yarrowia lipolytica was chosen as our study model thanks to its particularity since it is a strict aerobic microorganism with a high capacity to accumulate lipids and to produce organic acids. Experimental and analytical studies, using mathematical methods for modeling cell metabolism, allowed us to identify metabolic constraints involved in respiratory to fermentative transition in this yeast showing oxidative energy metabolism. Production of citric acid by Y. lipolytica, already reported in the literature, has been chosen as a marker for this in respiratory to fermentative shift. We found that the inhibition of the alternative oxidase protein (AOX) involved in mitochondrial respiration, by adding n-Propyl gallate (nPG) molecule improves the yield of citric acid production by fermentation of glucose in a Y. lipolytica culture. These results show that nPG, already used in food and pharmaceutical industry as a preservative, plays on respiratory to fermentative balance by inhibition of oxygen consumption and thus stimulates the production of citric acid. Modeling of the metabolic network of Y. lipolytica, described at genome-scale, by dynamic Flux Balance Analysis (FBA) has identified the accumulation of intracellular ROS (Reactive Oxygen Species) species as major levers for respiratory to fermentative shift and therefore the production of citric acid by Y. lipolytica. Therefore, our preliminary results show that oxidation of lipids accumulated by Y. lipolytica could be involved in generation of ROS species. This study must be experimentally deepened and constitutes an important contribution for the agri-food and pharmaceutical industry.Key words: Respiratory to fermentative shift, Citric acid, lipids, Yarrowia lipolytica, n-Propyl gallate, Reactive Oxygen Species, modeling, dynamic Flux Balance Analysis
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Submitted on : Saturday, October 19, 2019 - 1:03:17 AM
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Jorgelindo da Veiga Moreira. Modélisation de la bascule métabolique chez les cellules eucaryotes : application à la production de citrate chez la levure Yarrowia lipolytica. Biotechnologie. Université Paris Saclay (COmUE), 2019. Français. ⟨NNT : 2019SACLX015⟩. ⟨tel-02320659⟩

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