Bio-hydrogen production from cheese whey powder (CWP) solution: Comparison of thermophilic and mesophilic dark fermentations

Cheese whey powder (CWP) solution was used as the raw material for hydrogen gas production by mesophilic (35 °C) and thermophilic (55 °C) dark fermentations at constant initial total sugar and bacteria concentrations. Thermophilic fermentation yielded higher cumulative hydrogen formation (CHF = 171 mL), higher hydrogen yield (111 mL H 2  g −1 total sugar), and higher hydrogen formation rate (3.46 mL H 2  L −1  h −1 ) as compared to mesophilic fermentation. CHF in both cases were correlated with the Gompertz equation and the constants were determined. Despite the longer lag phase, thermophilic fermentation yielded higher specific H 2 formation rate (2.10 mL H 2  g −1 cells h −1 ). Favorable results obtained in thermophilic fermentation were probably due to elimination of H 2 consuming bacteria at high temperatures and selection of fast hydrogen gas producers.