Patent ID: 8372609

Claim:
A method of producing a concentrated sugar solution from biomass, the method comprising: a) delignifying biomass comprising the substeps of i) contacting with water and at least one nucleophilic base, a biomass comprising lignin and having a glucan/xylan weight ratio G 1 /X 1 to form a biomass slurry having a pH of about 12.5 to about 13.0; and ii) maintaining the biomass slurry under reaction conditions such that the slurry attains a pH of about 9.5 to about 10.0 and has a glucan/xylan weight ratio G 2 /X 2 within about 15% of the value of G 1 /X 1 , and wherein the slurry comprises a lignin-containing liquid fraction and a solid fraction comprising a polysaccharide enriched biomass; wherein G 1 and G 2 are grams of glucan per 100 grams of biomass and biomass slurry respectively, and X 1 and X 2 are grams of xylan per 100 grams of biomass and biomass slurry respectively; b) contacting with an aqueous acid solution comprising at least one mineral acid the solid fraction of the polysaccharide enriched biomass at reaction conditions sufficient to produce an intermediate saccharification product comprising xylose, xylan, and glucan, wherein the concentration of the solid fraction in the aqueous acid solution is about 13 weight percent to about 20 weight percent; and c) contacting with a saccharification enzyme consortium at a pH of from about 4.5 to about 5.5 the intermediate saccharification product at reaction conditions sufficient to produce a final saccharification product comprising at least about 7 percent by weight fermentable sugars, based on the total weight of the saccharification product, in 24 hours of contact with the saccharification enzyme consortium.