Fatty alcohol biosynthesis pathways. (A) Two different reaction schemes of fatty alcohol biosynthesis. Fatty alcohol could be synthesized via consecutive reduction reactions of a fatty acyl-CoA reductase and a fatty aldehyde reductase or via a single-step reduction of fatty acyl-CoA reductase. (B) Schematic view of fatty alcohol biosynthesis pathways in Synechocystis sp. PCC 6803 (Synechocystis). Solid lines show the native alka(e)ne and free fatty acid biosynthesis pathways in Synechocystis; dashed lines show the constructed fatty alcohol biosynthesis pathways in Synechocystis by knocking out the endogenous sll0208/sll0209 gene and heterologously expressing the fatty acyl-CoA reductase (maqu_2220) from Marinobacter aquaeolei VT8.