TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: The feedstock is incubated with 0.05-20 (preferably 5-10) FPU cellulase/g dry weight of feedstock or more. The feedstock is incubated for 10 minutes to 6 hours (preferably 15 minutes to 2 hours). The relative viscosity after treatment is less than 8000 cP (preferably less than 1500 cP). The pH is 2-6 (preferably 2-3 or 3-6). The feedstock is incubated at a temperature of 40-80 degrees C (preferably 50-60 degrees C). The feedstock is pretreated in an acidic solution prior to incubation with cellulase. The feedstock is pretreated in an acidic solution for 2 minutes to 2 hours. The feedstock is pretreated with steam for 1-3 hours prior to treatment with cellulase. The feedstock is treated with steam after treatment with an acidic solution. The method comprises: incubating the feedstock with 0.50-5 FPU cellulase/g dry weight of feedstock cellulase for 15 minutes to 2 hours, where the feedstock is incubated at a pH of 3 or less at a temperature of at least 60 degrees C and the relative viscosity after treatment is less than 1500 cP. The method comprises: combining the feedstock having a viscosity of at least 20000 cP with a feedstock obtained by treating a feedstock by the method, where the feedstock having a viscosity of at least 20000 cP comprises 30% or less of the volume of the feedstock treated by the method. Preferred Components: The acidic solution is phosphoric acid or sulfuric acid. The phosphoric acid solution comprises 0.01-10% (preferably 4-6) of phosphoric acid. The sulfuric acid solution comprises 0.01-10% (preferably 4-6%) of sulfuric acid. The feedstock prior to treatment comprises a mixture of 8-12 wt.% in an aqueous solution. The feedstock prior to treatment comprises a relative viscosity of at least 20000 cP. The method decreases relative viscosity of the feedstock by at least 50%, 60%, 70%, 80%, 90%, 92%, 95%, 97%, 98% or 99% as compared to the starting material. The method extracts at least 40%, 50%, 55%, 60% or 65% of the fermentable sugars from the feedstock. The fermentable sugars comprise one or more of xylose, galactose, and arabinose. The amount of fermentation inhibitors extracted by the method comprise less than 1%, less than 0.75%, less than 0.5% or less than 0.2% of the volume of the incubation mixture. The fermentation inhibitors comprise one or more of furfural, hydroxymethylfurfural, formate and acetate.