Figure 2

The metabolic pathways of 2-keto acid compounds and construction of the biological synthesis pathways in bioengineered strains for producing higher alcohols via fermentation by microbes. A: the common schematic pathways of S. cerevisiae (2-Oxocarboxylic acid metabolism: http://www.genome.jp/dbget-bin/www_bget?pathway:sce01210) and C. crenatum for producing 2-keto acid compounds. The genes LEU2, ILV5, ILV2, ILV3, LEU4, LEU1, BAT1 and BAT2 play a role in the synthesis of 2-keto acids in S. cerevisiae. The genes Cgl 1315, Cgl 1286, Cgl 1271, Cgl 1273, Cgl 1268, Cg1 0248 and Cgl 2204 act as catalysts in the production of 2-keto acids in C. crenatum. LEU2, Cgl 1286:3-isopropylmalate dehydrogenase. ILV5, Cgl 1273:ketoacid reductiove isomerase. ILV2, Cgl 1271:acetyl lactic acid synthase. ILV3, Cgl 1268: dihydroxy acid dehydratase. LEU4, Cg1 0248:2-isopropyl malic acid synthase. LEU1, Cgl 1315: 3-isopropylmalate dehydratase. BAT1, BAT2, Cgl 2204: branched-chain amino acid transaminase. B: construction of the metabolic pathways for higher alcohol production in C. crenatum based on 2-Keto acid pathways; ADH2: Alcohol dehydrogenase; Kivd: alpha-ketoisovalerate decarboxylase. Metabolic pathway A: LEU2-ILV2-ILV5 + KIVD-ADH2; Metabolic pathway B: ILV2-ILV5-ILV3 + KIVD-ADH2; Metabolic pathway C: BAT2 + KIVD-ADH2; Metabolic pathway D: LEU4-LEU1 + KIVD-ADH2; Metabolic pathway E: LEU1 + KIVD-ADH2.