Production of cellulosic ethanol and hydrogen from solid-state enzymatic treated cornstalk: a two-stage process

A two-stage process combining cellulosic ethanol and hydrogen production from solid-state enzymatic treated cornstalk was investigated in this study. A three-factor, five-level central composite design (CCD) with temperature (X(1)), compound enzyme dosage (X(2)) and time (X(3)) as the independent variables was applied to optimizing technological parameters of solid-state enzymatic hydrolysis of cornstalk for cellulosic ethanol and hydrogen production. Experimental results showed that X(1), X(2) and X(3) all had an individual significant influence on ethanol production, but were insignificant on the subsequent hydrogen production. In the first stage, the maximum ethanol yield from cornstalk by Pachysolen tannophilus As2.1585 was 234.1 mg/g-total volatile solid (TVS) at 47.9 degrees C of temperature, 0.054 g/g-cornstalk of compound enzyme dosage and 10.46 days of reaction time. In the second stage, 66.9 mL/g-TVS of hydrogen was produced from the effluent of the first stage by mixed culture. The energy recovery of 50.9% showed that combine ethanol-hydrogen production possessed high energy efficiency. The ethanol was attributed to the bioconversion of the generated soluble sugars from the enzymatic hydrolysis of corn stalk and the hydrogen was mainly due to the biodegradation of hemicellulose and cellulose from residue of corn stalk after producing ethanol.