Enhanced bio-hydrogen production by anaerobic fermentation of apple pomace with enzyme hydrolysis

A series of batch experiments were conducted to investigate the effects of the HCl-pretreated concentrations, enzyme hydrolysis time and temperature, the cellulase dosage, the ultrasonic time and the fermentation substrate concentration on hydrogen (H2) production from the anaerobic fermentation of apple pomace (AP). The natural mixed microorganisms from river sludge was used as the seed after being boiled for 15 min. A maximum cumulative H2 yield (CHYm) of 134.04 ml/g total solid (TS) and an average H2 production rate (AHPR) of 12.00 ml/g TS/h were obtained from the fermentation of the enzyme-hydrolyzed AAP (a AP soaked with 6% ammonia liquor for 24 h) at the substrate concentration of 15 g/L. The optimal enzyme hydrolysis conditions were proposed as follows: AAP with a cellulase dosage of 12.5 mg/g TS at the hydrolysis substrate concentration of 20 g/L after the ultrasonic irradiation for 20 min was hydrolyzed by the enzyme catalysis at 45 °C and initial pH 5.0 for 48 h.