Hydrogen production by Escherichia coli depends on glucose concentration and its combination with glycerol at different pHs

Escherichia coli produces molecular hydrogen (H2) during glucose or mixed carbon (glucose and glycerol) fermentation. Dependence of H2 production rate ( V H 2 ) on glucose at different pHs was studied in a concentration dependent manner. During growth of wild-type on glucose, increasing glucose concentration from 0.05% to 0.2% resulted in the marked inhibition of V H 2 . Inhibitory effect of glucose was shown at pH 7.5 and 6.5 but not pH 5.5. However, glycerol added in the growth medium with 0.1% glucose significantly increased V H 2 but different effects at different pHs were established upon glucose or glycerol assays. The results indicate that H2 production is inhibited by glucose in a concentration dependent manner during glucose fermentation but glucose in combination with glycerol might enhance H2 production during mixed carbon fermentation.