Patent ID: 7727746

Claim:
A process for the enzymatic hydrolysis of cellulose to produce glucose from a pre-treated cellulosic feedstock, the process comprising: i) providing an aqueous slurry of the pre-treated cellulosic feedstock, the slurry comprising from about 3% to about 30% undissolved solids in a liquid, the undissolved solids comprising at least about 20% cellulose; ii) introducing the aqueous slurry at the bottom of an unmixed hydrolysis reactor having a height of between about 5 and about 75 feet and a height-to-diameter ratio of between about 0.5 and about 10 and limiting axial dispersion in the unmixed hydrolysis reactor by pumping the slurry upwardly at a velocity that corresponds to an average slurry flow velocity in said unmixed hydrolysis reactor of about 0.1 to about 12 feet per hour, and wherein the undissolved solids flow upward at a rate slower than that of the liquid; iii) adding cellulase enzymes and β-glucosidase to the aqueous slurry before or during the step of introducing (step ii), or a combination thereof, wherein the cellulase enzymes hydrolyze the cellulose to produce the glucose and wherein the glucose so produced has a higher concentration at the top of the unmixed hydrolysis reactor than at its bottom; and iv) removing an aqueous upflowing stream comprising at least the glucose from the unmixed hydrolysis reactor.