Fig. 2.

Metabolic engineering of Y. lipolytica to improve succinic acid production from glycerol. a. Schematic diagram of metabolic pathway optimization. Glu: Glucose; GAP: Glyceraldehyde 3-phosphate; Cit: Citrate; SA: Succinate; 3 PG: 3-phosphoglycerate; Fum: Fumarate; Icit: Isocitrate; PEP: Phosphoenolpyruvate; Succ: Succinyl-CoA; OAA: Oxaloacetate; Pyr: Pyruvate; DHAP: Dihydroxyacetone phosphate; Ac-CoA: Acetyl-CoA; Gly: Glycerol; G3P: 3-phosphoglycerol; α-KG: α-ketoglutarate. Pck: Phosphoenolpyruvate carboxykinase; Kgdh: α-ketoglutarate dehydrogenase; Pyrc: Pyruvate carboxylase; Ach1: Acetyl-CoA hydrolase; Icl: Isocitrate lyase; Scs2: Succinyl-CoA synthase. b. Optimization of metabolic pathways. “-” indicates the absence of metabolic engineering manipulation. “+” indicates gene integration into the genome; “Δ” indicates gene knockout. c. Production of succinic acid by strain ST-109 in a 5-L bioreactor. d. The succinic acid titer and yield of strain ST-109 were measured at different time points in a 5-L bioreactor.