Improved Xylan Hydrolysis of Corn Stover by Deacetylation with High Solids Dilute Acid Pretreatment

To produce ethanol cost-effectively from herbaceous feedstocks such as corn stover, efficient xylan hydrolysis with monomeric xylose yields approaching 90% are necessary. Dilute acid pretreatment is well established as one of the pretreatment technologies for xylan hydrolysis; however, the accumulation of salts from neutralization, the production of toxic byproducts, and the release of acetic acid can inhibit enzymatic saccharification and fermentation, resulting in depressed ethanol yields. Successful removal of acetyl groups from native corn stover by alkali de-esterification could potentially increase monomeric xylose yields from pretreatment and enzymatic hydrolysis, improve cellulose digestibility, and reduce the cytotoxicity of the fermentation broth. Results presented in this article show that alkaline extraction removed significant amounts of acetyl groups from corn stover, improved xylan hydrolysis in high solids dilute acid pretreatment by more than 50%, and improved xylan and glucan hydrolysis in low solids enzymatic hydrolysis by 15% and 30% over control samples. In whole slurry enzymatic hydrolysis, a 30% improvement in cellulose digestibility was found over the control.