Fig. 3.

Influence of the cell density on volumetric and specific H₂ production rates. Cells were grown with 20 mM fructose, harvested in the exponential growth phase, and suspended in buffer (50 mM imidazole, 20 mM KCl, 20 mM MgSO₄, 30 µM ETH2120, 20 mM NaCl, 4 mM DTE, pH 7) to a final protein concentration of 0.5–4 mg mL⁻¹ (corresponding to a CDW of 1.2–9.7 g L⁻¹). Experiments were started by the addition of 100 mM sodium formate. Initial specific H₂ production rates (squares) or initial volumetric H₂ production rates (circles) are plotted against the cell density used