Process and apparatus for enzymatic hydrolysis of lignocellulosic material and fermentation of sugars

Abstract

The invention relates to a process for the preparation of a sugar product from lignocellulosic material, comprising the following steps: a) optionally, pretreatment of the lignocellulosic material; b) optionally, washing of the optionally pretreated lignocellulosic material; c) enzymatic hydrolysis of the optionally washed and/or optionally pretreated lignocellulosic material in a hydrolysis reactor using an enzyme composition comprising at least two cellulase; and d) optionally, recovery of a sugar product; wherein during the enzymatic hydrolysis oxygen-containing gas is added to the lignocellulosic material in the hydrolysis reactor and wherein part of the oxygen-containing gas, added to the lignocellulosic material, is gas originating from the headspace of the reactor, preferably during part of the time of the enzymatic hydrolysis less oxygen is added to the lignocellulosic material compared to the other part of the time of the enzymatic hydrolysis, or preferably during part of the time of the enzymatic hydrolysis no oxygen is added to the lignocellulosic material.

1 . An apparatus which comprises:
 a) a reactor of at least 1 m 3  which comprises a gas introducing means for introduction of gas in the reactor;   b) optionally, at least one stirring means for stirring the reactor contents;   c) a gas pump connected to the gas introducing means for introducing gas into the reactor;   d) a recycle pipe connected at an end of the recycle pipe to the headspace of the reactor and connected at another end of the recycle pipe to the gas pump;   e) an exhaust connected to the recycle pipe, for deleting gas from the reactor headspace;   f) a gas inlet for introducing fresh gas in the reactor, said gas inlet connected to the gas pump via the recycle pipe;   g) a means for controlling the ratio between recycled gas and fresh gas.   
     
     
         2 . The apparatus of  claim 1 , wherein the gas introducing means is a gas sparger that is located adjacent to a bottom surface inside of the reactor. 
     
     
         3 . The apparatus of  claim 2 , wherein the gas sparger is located adjacent to a bottom surface inside of the reactor. 
     
     
         4 . The apparatus of  claim 3 , wherein the gas sparger comprises nozzles or orifices for introduction of the gas into the reactor. 
     
     
         5 . The apparatus of  claim 4 , wherein the gas sparger nozzles or orifices comprise holes with a diameter between 0.5 mm and 500 mm. 
     
     
         6 . The apparatus of  claim 5 , wherein the gas sparger covers a large part of the bottom surface inside of the reactor. 
     
     
         7 . The apparatus of  claim 1 , wherein the means for controlling the ratio between gas recycled from the reactor headspace and fresh gas permits continuous addition of gas and discontinuous addition of gas. 
     
     
         8 . The apparatus of  claim 1 , wherein the means for controlling the ratio between gas recycled from the reactor headspace and fresh gas is a valve. 
     
     
         9 . The apparatus of  claim 1 , comprising at least one stirring means for stirring the reactor contents. 
     
     
         10 . The apparatus of  claim 1  which does not comprise any stirring means for stirring the reactor contents. 
     
     
         11 . The apparatus of  claim 1 , further comprising a venturi tube for circulating a liquid portion of the reactor contents, whereby the circulation of fluid through the venturi tube drives the introduction of the gas into the reactor.