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

The inhibition of competitive metabolic pathways by various inhibitors in order to redirect electron flow towards nitrogenase and bidirectional Hox-hydrogenase was investigated in Anabaena siamensis TISTR 8012. Cells grown in BG110 supplemented with KCN, rotenone, DCMU, and DL-glyceraldehyde under light condition for 24 h showed enhanced H2 production. Cells grown in BG11 medium showed only marginal H2 production and its production was hardly increased by the inhibitors tested. H2 production with either 20 mM KCN or 50 μM DCMU in BG110 medium was 22 μmol H2 mg chl a−1 h−1, threefold higher than the control. The increased H2 production caused by inhibitors was consistent with the increase in the respective Hox-hydrogenase activities and nifD transcript levels, as well as the decrease in hupL transcript levels. The results suggested that interruption of metabolic pathways essential for growth could redirect electrons flow towards nitrogenase and bidirectional Hox-hydrogenase resulting in increased H2 production.