Fig. 4

Metabolic pathway for the production of free fatty acids (FFAs) via fatty acid elongation cycle and reversed β-oxidation cycle. Strategies used to increase the yield of FFAs include (1) enhancement of precursor supply by overexpression of acetyl-CoA carboxylase (ACC); (2) repression of FFAs consumption via the deletion of acyl-CoA synthetase (fadD); (3) enhancement of fatty acid elongation cycle via the overexpression of (3R)-hydroxymyristoyl-ACP dehydrase (fabZ); (4) enhancement of NADPH generation via the overexpression of NAD kinase (nadK) and membrane-bound transhydrogenase (pntAB). ACC acetyl-CoA carboxylase; fabZ: (3R)-hydroxymyristoyl-ACP dehydrase; fadA, thiolase; fadB, functional hydroxyacyl-CoA dehydrogenase and enoyl-CoA hydratase; fadD: acyl-CoA synthetase; nadK NAD kinase; pntAB membrane-bound transhydrogenase; TE thioesterase; ydiO, enoyl-CoA reductase