TECHNOLOGY FOCUS - BIOLOGY - Preferred Process: The part of the time, when less or preferably no oxygen is added, is 10-80%, preferably 40-80% of the total enzymatic hydrolysis time. The part of the time, when more oxygen is added, is 2-80%, preferably 10-50% of the total enzymatic hydrolysis time. The part of the time is: 12-50%, preferably 20-40%, when the more oxygen is added in second half of time of the enzymatic hydrolysis; and/or 2-30%, preferably 5-20% of the total enzymatic hydrolysis time, when the more oxygen is added in the first half of time of the enzymatic hydrolysis. The oxygen concentration in the liquid phase of the hydrolysis during the part of the time, when oxygen is added, is at least 2 times, preferably at least 10 times of the oxygen concentration in the liquid phase during the part of the time, when less or no oxygen is added. In the part of the time when the oxygen is added, the oxygen concentration in the liquid phase, when the lignocellulosic material is present during the enzymatic hydrolysis, is at least 0.001 mole/m3, preferably at least 0.003 mole/m3, or in the part of the time when the oxygen is added, the oxygen concentration in the liquid phase, when the lignocellulosic material is present during the enzymatic hydrolysis, is at most 0.12 mole/m3, preferably at most 0.03 mole/m3. The oxygen is added in the form of bubbles. The reactor for the enzymatic hydrolysis has a volume of 1 m3 or more. The enzymatic hydrolysis time is 5-150 hours. The enzyme composition retains activity for 30 hours or more. The hydrolysis is conducted at a temperature of 45 degrees C or more, preferably 55 degrees C or more. The enzyme composition is derived from a fungus, preferably a microorganism of genus Rasamsonia or the enzyme composition comprises a fungal enzyme preferably a Rasamsonia enzyme. The dry matter content in the hydrolysis step (c) is 10 wt.% or more, preferably 14-33 wt.%. The enzymatic hydrolysis process takes place in a batch, fed batch and/or continuous culture reactor. The oxygen is introduced as an oxygen-containing gas such as air. EXAMPLE - No suitable example given.