2.3. Hydrolysis
Hydrolysis of 16.6% (w/v) coffee pulp suspension was first carried out at 121 C for 30 min in presence of 0.18 mol L1 H2SO4. Afterwards the pH was adjusted manually to 5 by adding 20% (w/w) NaOH. As a second step the chemically pretreated coffee pulp was enzymatically hydrolyzed using Accellerase 1500. Per gram of initially added coffee pulp 0.3 mL of Accellerase 1500 was added and the reaction carried out stirred (150 rpm) at 50 C for 24 h in a 2 L BIOSTAT bioreactor . Hydrolysis was evaluated for the total amount of sugar released after hydrolysis compared to the theoretically available sugars in the coffee pulp. The theoretical amount of sugar was calculated from the sugar content of the substrate and the cellulose and hemicellulose contents. For cellulose a suggested conversion factor of 0.9 was used according to . Since the structure of hemicellulose could not be determined an estimated conversionfactor of 0.9 was used.