Figure 1

Schematic illustration of the metabolic pathway leading to biobutyrate from glucose. The strategy of metabolic engineering was applied to rewire EcN metabolism for the synthesis of biobutyrate. Pathways of enhancement and of new construction were indicated by solid lines (blue) while pathways of blockage were marked with “X” (dotted lines). The genetic construction resulted in the bacterial vector including EcN-BUT (top) and EcN-ato (bottom). After the fermentation, the bacterial production of acetate (mM) or biobutyrate (mM) was indicted in the Figure. Acetate is produced during the biosynthesis of Arg from 2-KG and of Cys from 3-PG in EcN-BUT. The genes involves in the metabolic pathway: aceEF pyruvate dehydrogenase complex, adhE aldehyde-alcohol dehydrogenase, atoDA acetoacetyl-CoA transferase, pta phosphate acetyltransferase, poxB pyruvate oxidase, phaA β-ketothiolase, hbd 3-hydroxybutyryl-CoA dehydrogenase, crt crotonase, ter trans-enoyl-CoA reductase. Arg argine, Cys cysteine, 2-KG 2-ketoglutarate, PEP phosphoenolpyruvate, 3-PG 3-phosphoglycerate, Pry pyruvate.