Patent ID: 7993463

Claim:
A method of producing a fermentation product, comprising in this order: a) leaching a lignocellulosic feedstock comprising greater than about 20% (w/w) cellulose to reduce the level of compounds in said feedstock that interfere with a subsequent treatment with acid, said leaching comprising contacting said feedstock with at least one aqueous solution for a period greater than about 2 minutes, said aqueous solution having a pH of between about 6 and about 9, to produce a leached feedstock and a leachate; b) removing said leachate from said leached feedstock; c) acidifying said leached feedstock with acid to a pH between about 0.5 and about 3 to produce an acidified feedstock; d) pretreating said acidified feedstock subsequent to step (c) under conditions to disrupt fiber structure to increase the accessibility of the leached feedstock to being hydrolyzed, to produce a composition comprising xylose and a pretreated feedstock; e) treating said composition comprising xylose and pretreated feedstock with cellulase under conditions which hydrolyse cellulose in said pretreated feedstock to glucose, producing a sugar solution comprising xylose and glucose; and f) treating said sugar solution with a microorganism under conditions which permit fermentation of said xylose and/or said glucose to the fermentation product.