Escherichia coli hydrogenase activity and H2 production under glycerol fermentation at a low pH

Hydrogenase (Hyd) activity and H-2 production by Escherichia coli were studied at a low pH. H-2 production at pH 5.5 under glycerol fermentation was shown to be similar to 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-2 production inhibition was increased with decreasing pH and almost maximal inhibition was observed at pH 5.5. The data on H-2 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-2 producing mode. Moreover, a role of fhlA gene in Hyd-3 and Hyd-4 activity in H-2 production is proposed under glucose fermentation at a low pH. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.