Treatment with moderate concentrations of NaHSO3 enhances photobiological H2 production in the cyanobacterium Anabaena sp. strain PCC 7120

In cyanobacteria, treatment with low concentrations of NaHSO3 can enhance photosynthetic efficiency, whereas NaHSO3 in high amounts often inhibits cell growth and photosynthesis may even cause death. In the present study, our results showed that treatment with moderate concentrations of NaHSO3 considerably improved the yield of photobiological H2 production in the filamentous N2-fixing cyanobacterium Anabaena sp. strain PCC 7120. Under steady state conditions, the accumulated H2 levels in cells treated with 1 mM NaHSO3 were approximately 10 times higher than that in untreated cells. Such improvement occurred in heterocysts and was most likely caused by increases in the expression and activity of nitrogenase. The effects of treatment with low, moderate, and high concentrations of NaHSO3 in cyanobacteria were proposed on the basis of the results obtained in the present study and from previous knowledge.