Design and optimization of hydrogen production from hydrothermally pretreated sugarcane bagasse using response surface methodology

Hydrogen production from hydrothermally pretreated (200 degrees C for 10 min at 16 bar) sugarcane bagasse was analyzed using response surface methodology. The yeast extract concentration and the temperature had a significant influence for hydrogen production (p-value 0.027 and 0.009, respectively). Maximum hydrogen production (17.7 mmol/L) was observed with 3 g/L yeast extract at 60 degrees C (C10). In this conditions were produced acetic acid (50.44 mg/L), butyric acid (209.71 mg/L), ethanol (38.4 mg/L), and methane (6.27 mmol/L). Lower hydrogen productions (3.5 mmol/L and 3.9 mmol/L) were observed under the conditions C7 (2 g/L of yeast extract, 35.8 degrees C) and C9 (1 g/L of yeast extract, 40 degrees C), respectively. The low yeast extract concentration and low temperature caused a negative effect on the hydrogen production. By means of denaturing gradient gel electrophoresis 20% of similarity was observed between the archaeal population of mesophilic (35 and 40 degrees C) and thermophilic (50, 60 and 64 degrees C) reactors. Likewise, similarity of 22% was noted between the bacterial population for the reactors with the lowest hydrogen production (3.5 mmol/L), at 35.8 degrees C and with the highest hydrogen production (17.7 mmol/L) at 60 degrees C demonstrating that microbial population modification was a function of incubation temperature variation.