Method of obtaining a product sugar stream from cellulosic biomass

A process for producing ethanol comprising:

• a) obtaining cellulosic biomass from a feedstock selected from the group consisting of an agricultural waste, corn stover, wheat straw, barley straw, canola straw, oat straw, rice straw, soybean stover, a grass, switch grass, miscanthus, cord grass, reed canary grass, a forestry residue, aspen wood or sawdust, a sugar residue, bagasse and beet
• b) pretreating the cellulosic biomass at a pH of about 0.4 to about 2.0 by adding one or more than one acid to the cellulosic biomass to hydrolyze a portion of the cellulose and at least a portion of the hemicellulose in the cellulosic biomass to produce a pretreated cellulosic biomass comprising glucose, acetic acid and a sugar monomer selected from the group consisting of xylose, arabinose, mannose, galactose and a combination thereof;
• c) adding one or more than one base to the pretreated cellulosic biomass to adjust the pretreated cellulosic biomass to a pH of about 4.0 to about 6.0, thereby producing a neutralized cellulosic biomass comprising inorganic salt and acetate salt;
• d) hydrolyzing the neutralized cellulosic biomass with cellulase enzymes to produce a crude sugar stream;
• e) separating insoluble residue from the crude sugar stream to produce a clarified sugar stream;
• f) treating the clarified sugar stream using ion exclusion chromatography with a cation exchange resin at a pH from about 5.0 to;
• about 10.0 to produce one or more than one raffinate stream comprising the inorganic salt and acetate salt and a product sugar stream comprising sugar, wherein the concentration of acetic acid plus acetate salt in the clarified sugar stream fed to the ion exclusion chromatography step is greater than about 5 g/L;
• g) recovering the product sugar stream, and the one or more than one raffinate stream;
• and
• h) fermenting the sugar, in the product sugar stream to ethanol.

A process for obtaining a product sugar stream from a crude sugar stream, the crude sugar stream produced from conversion of cellulosic biomass to sugar, the process comprising:

• a) separating insoluble residue from the crude sugar stream to produce a clarified sugar stream;
• b) treating the clarified sugar stream using ion exclusion chromatography at about pH 5.0 to about 10.0 to produce one or more than one raffinate stream comprising sulfate and acetate salts, and a product stream comprising sugars wherein the concentration of acetic acid plus acetate salt in the clarified sugar stream fed to the ion exclusion chromatography step is greater than about 5 g/L;
• and
• c) obtaining the product sugar stream.