Redirecting the electron flow towards the nitrogenase and bidirectional Hox-hydrogenase by using specific inhibitors results in enhanced H2 production in the cyanobacterium Anabaena siamensis TISTR 8012

► Photosynthetic cyanobacterial based H2 production is limited by electron supply. ► Redirecting competing pathways for electron flow results in increased H2 production. ► Metabolic engineering leads to increased production of desired product.