Fig. 6
a–c Specific H2 productivity versus the ratio of the maximum dissolved-H2 concentration on the critical dissolved-H2 concentration \(\left( {\left[ {{\text{H}}_{2} } \right] /\left[ {{\text{H}}_{{ 2 {\text{crit}}}} } \right]} \right)\) predicted by the mathematical model at various inlet N2 flow rates (5, 10, 20, and 100 mL/min). a For three yeast extract concentrations: (filled circle) 0.1 g/L, (open circle) 0.25 g/L, and (filled square box) 0.5 g/L. Glucose and thiosulfate concentrations were 50 and 0.12 mmol/L, respectively. b For three thiosulfate concentrations: (filled circle) 0 mmol/L, (open circle) 0.03 mmol/L, and (filled square box) 0.06 mmol/L. Glucose and yeast extract concentrations were 50 mmol/L and 1 g/L, respectively. c For four glucose concentrations: (filled circle) 0 mmol/L, (filled square) 5 mmol/L, (open circle) 10 mmol/L, and (filled square box) 20 mmol/L. Thiosulfate and yeast extract concentrations were 0.12 mmol/L and 1 g/L, respectively. For these three model predictions one of the variables (glucose, yeast extract, and thiosulfate concentrations) is growth-limiting