Effect of initial bacteria concentration on hydrogen gas production from cheese whey powder solution by thermophilic dark fermentation.

Dark fermentative hydrogen gas production from cheese whey powder solution was realized at 55°C. Experiments were performed at different initial biomass concentrations varying between 0.48 and 2.86 g L⁻¹ with a constant initial substrate concentration of 26 ± 2 g total sugar (TS) per liter. The highest cumulative hydrogen evolution (633 mL, 30°C), hydrogen yield (1.56 mol H₂ mol⁻¹ glucose), and H₂ formation rate (3.45 mL h⁻¹) were obtained with 1.92 g L⁻¹ biomass concentration. The specific H₂ production rate decreased with increasing biomasss concentration from the highest value (47.7 mL g⁻¹ h⁻¹) at 0.48 g L⁻¹ biomass concentration. Total volatile fatty acid concentration varied beetween 10 and 14 g L⁻¹ with the highest level of 14.2 g L⁻¹ at biomass concentration of 0.48 g L⁻¹ and initial TS content of 28.4 g L⁻¹. The experimental data were correlated with the Gompertz equation and the constants were determined. The most suitable initial biomass to substrate ratio yielding the highest H₂ yield and formation rate was 0.082 g biomass per gram of TS. © 2012 American Institute of Chemical Engineers Biotechnol. Prog., 28: 931-936, 2012 [ABSTRACT FROM AUTHOR]