초록
Hydrogenase (Hyd) activity and H<SUB>2</SUB> production by Escherichia coli were studied at a low pH. H<SUB>2</SUB> production at pH 5.5 under glycerol fermentation was shown to be ∼1.5-fold higher than that at pH 6.5 or above but less than that under glucose fermentation. It was inhibited by N,N'-dicyclohexylcarbodiimide: H<SUB>2</SUB> production inhibition was increased with decreasing pH and almost maximal inhibition was observed at pH 5.5. The data on H<SUB>2</SUB> production by single and double mutants with defects in different Hyd-enzymes and in fhlA gene suggest that under glycerol fermentation at a low pH, Hyd-1, Hyd-2 and Hyd-4 were operating in a reversed, non-H<SUB>2</SUB> producing mode. Moreover, a role of fhlA gene in Hyd-3 and Hyd-4 activity in H<SUB>2</SUB> production is proposed under glucose fermentation at a low pH.