Improvement of biohydrogen production under decreased partial pressure of H2 by Enterobacter cloacae

When the partial pressure of H-2 was decreased by lowering the total pressure in the headspace of the reactor in a batch fermentation process from 760 mm Hg to 380 mm Hg containing Enterobacter cloacae, the molar yield of H-2 increased from 1.9 mol to 3.9 mol H-2/mol glucose. The maximum production rate was 0.017 mmol H-2/h l at 380 mm Hg. The lag period as well as total batch time of H-2 production decreased using a decreased partial pressure.