A method to treat a lignocellulosic material including: pretreating the lignocellulosic material to produce a slurry; adding an alkali material to the slurry in a first conveyor; adding a first portion of an enzyme solution to the slurry while the slurry is in, entering or passing through the discharge of a second conveyor; transferring the slurry with the enzyme solution from the second conveyor slurry to a mixer; mixing the slurry with a second portion of the enzyme solution, and transferring the slurry with the enzyme solution mixed with the first and second portions of the enzyme solution to a first reactor vessel for enzymatic hydrolysis, wherein the viscosity of the slurry is reduced in the first reactor vessel.