Enhanced hydrogen production from cornstalk by dark- and photo-fermentation with diluted alkali-cellulase two-step hydrolysis

The effect of a two-step cornstalk pretreating process, NaOH delignification followed by enzymolysis with cellulase and hemicellase, on dark- and photo-fermentative H2 production was studied. A five-factor and five-level orthogonal experimental array was designed and conducted to study the effect of NaOH concentration (0-1%), hydrolysis time (0-3 h), hydrolysis temperature (98-126 °C), cellulase (0-18 IU/g-cornstalk) and hemicellulase dosage (0-2400 IU/g-cornstalk) on pretreatment efficiency determined by H2 production. With NaOH 0.75%, hydrolysis temperature 108 °C, hydrolysis time 0.5 h, cellulase dosage 12 IU/g-CS and hemicellulase 2400 IU/g-CS, a maximum reducing sugar yield of 0.56 ± 0.03 g/g-CS and maximum H2 yield of 163.1 mL-H2/g-cornstalk were obtained under dark-fermentation, and a maximum H2 yield of 339.5 mL-H2/g-cornstalk was obtained under photo-fermentation. According to the results, the significance of the five parameters on H2 production was listed in high-to-low order as: NaOH concentration, cellulase dosage, hydrolysis temperature, hemicellulase and hydrolysis time. The effect of the alkaline delignification on pretreatment efficiency and the future efforts on improving H2 production from agricultural wastes were also discussed.