Enhancement effect of l-cysteine on dark fermentative hydrogen production

By adding a small amount of l-cysteine (0.1–1.0 mM) to nutrient solution, the dark fermentative hydrogen production using anaerobic mixed culture at two mesophilic temperatures, 35 °C and 30 °C, were largely enhanced. Compared to those of the blank tests, the hydrogen productivities and substrate degradation efficiencies of the tests with l-cysteine were all increased. Moreover, the maximum hydrogen production rates were increased to 1.5–2.9 times. In particular, the hydrogen yields peaked at 3.10 mol H2/mol sucrose with addition of 0.6 mM l-cysteine at 35 °C and at 3.28 mol H2/mol sucrose with addition of 0.1 mM l-cysteine at 30 °C, which were 15.2% and 70% higher than those of the corresponding blank ones, respectively. The results show that l-cysteine can be used as a low-cost and highly efficient bioactive agent to increase dark fermentative hydrogen production.