A catalytic alkaline hydrogen peroxide (cAHP) pretreatment method for corn stover and optimization

Abstract

Corn stover is residual biomass that can be used for the production of fermentable sugars through enzymatic hydrolysis. However, a pretreatment step is required to enhance the enzymatic digestibility of biomass. Even though the alkaline hydrogen peroxide (AHP) method shows promise as an effective pretreatment for corn stover, a typical reaction time of 24 h is too long, and the amount of hydrogen peroxide required (~5% w/v) is too high. To address this problem, we developed a novel catalytic alkaline hydrogen peroxide (cAHP) method to shorten the pretreatment time and reduce hydrogen peroxide usage. This is the first time a metal catalyst, iron tetraamidomacrocyclic ligand (Fe-TAML) is combined with AHP to accelerate the oxidation of lignin using hydrogen peroxide under an alkaline condition. The reaction time can be shortened to 4.4 h from a typical reaction time of 24 h. With 5 ppm of Fe-TAML, the reducing sugar concentration is increased by 15% to 27.9 g/L, compared to the one without Fe-TAML. Next, the cAHP method is optimized by using response surface methodology (RSM). After the pretreatment of 10% corn stover in an alkaline solution (pH 10) with 8850 ppm H2O2 and 0.91 ppm catalyst for 4.4 h, the residual biomass can be recovered and hydrolyzed by using 10 U/mL at 12% solid loadings. After 24 h of hydrolysis, 36.2 g/L of reducing sugar is obtained, representing a 39.6% increase compared to traditional AHP using the same optimized condition.