Fig. 3

Metabolic pathways and metabolic engineering strategies for the production of 1,3-propanediol (1,3-PDO). 1,3-PDO can be produced from glucose by glycerol-dependent pathway (route ①, illustrated by green colors) or by a non-natural homoserine-derived pathway (route ②, illustrated by yellow colors). To generate a 1,3-PDO hyperproducer via glycerol-dependent pathways, different byproduct synthetic pathways should be blocked as illustrated by red cross marks. ackA acetate kinase, aldA/aldB aldehyde dehydrogenases, edd 6-phosphogluconate dehydratase, galP galactose-proton symporter, glk glucose kinase, gdh ^K92V/T195S glutamate dehydrogenase with point mutation of K92V/T195S, gpd1 glycerol 3-phosphate dehydrogenase, gpp2 glycerol 3-phosphate phosphatase, gldA glycerol dehydrogenase, glpK glycerol kinase, mgsA methylglyoxal synthase, ndh NADH dehydrogenase II, pdc pyruvate decarboxylase, pta phosphate acetyltransferase, ptsHI components of phosphoenolpyruvate-dependent phosphotransferase system, yqhD/dhaT alcohol dehydrogenase