title: 13C Metabolic Flux Analysis of acetate conversion to lipids by Yarrowia lipolytica.
abstract: Volatile fatty acids (VFAs) are an inexpensive and renewable carbon source that can be generated from gas fermentation and anaerobic digestion of fermentable wastes. The oleaginous yeast Yarrowia lipolytica is a promising biocatalyst that can utilize VFAs and convert them into triacylglycerides (TAGs). However, currently there is limited knowledge on the metabolism of Y. lipolytica when cultured on VFAs. To develop a better understanding, we used acetate as the sole carbon source to culture two strains, a control strain and a previously engineered strain for lipid overaccumulation. For both strains, metabolism during the growth phase and lipid production phase were investigated by metabolic flux analysis using two parallel sodium acetate tracers. The resolved flux distributions demonstrate that the glyoxylate shunt pathway is constantly active and the flux through gluconeogenesis varies depending on strain and phase. In particular, by regulating the activities of malate transport and pyruvate kinase, the cells divert only a portion of the glyoxylate shunt flux required to satisfy the needs for anaplerotic reactions and NADPH production through gluconeogenesis and the oxidative pentose phosphate pathway (PPP). Excess flux flows back to the tricarboxylic acid (TCA) cycle for energy production. As with the case of glucose as the substrate, the primary source for lipogenic NADPH is derived from the oxidative PPP.
authors.affiliation: Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
authors.forename: Nian
authors.initials: N
authors.lastname: Liu
authors.affiliation: Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
authors.forename: Kangjian
authors.initials: K
authors.lastname: Qiao
authors.affiliation: Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. Electronic address: gregstep@mit.edu.
authors.forename: Gregory
authors.initials: G
authors.lastname: Stephanopoulos
mesh_terms: D000085:Acetates / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D002250:Carbon Radioisotopes / Q000493:pharmacokinetics; D066241:Carbon-13 Magnetic Resonance Spectroscopy / Q000379:methods*; D002952:Citric Acid Cycle / Q000502:physiology; D003198:Computer Simulation; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D005943:Gluconeogenesis / Q000502:physiology; D008055:Lipids / Q000096:biosynthesis*; D060847:Metabolic Engineering; D064688:Metabolic Flux Analysis / Q000379:methods*; D008954:Models, Biological; D010427:Pentose Phosphate Pathway / Q000502:physiology*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D025062:Yarrowia / Q000378:metabolism*
chemical_list: D000085:Acetates; D001426:Bacterial Proteins; D002250:Carbon Radioisotopes; D008055:Lipids; D019275:Radiopharmaceuticals
keywords: (13)C Metabolic Flux Analysis; Acetate metabolism; Biodiesel; Gluconeogenesis; NADPH; Yarrowa lipolytica