OPTIMIZATION OF TEMPERATURE AND ENZYME CONCENTRATION IN THE ENZYMATIC SACCHARIFICATION OF STEAM-PRETREATED WILLOW

The effect of temperature and enzyme concentration on the enzymatic hydrolysis of steam-pretreated willow was investigated to obtain the optimal hydrolysis conditions. The willow was pretreated at 220°C for 10 min according to the results of earlier optimization studies of the steam-pretreatment conditions for high glucose yields. The concentrations of two commercial enzymes, Celluclast 2L and Novozyme 188, were varied in the range 0-20% (based on oven-dry substrate). A maximum in the conversion of cellulose to glucose was obtained using a mixture of 15% Celluclast and 3% Novozyme, corresponding to an activity of 11.4 FPU g-1 substrate. Higher enzyme concentrations did not increase the initial hydrolysis rate nor affect the final glucose yield. The effects of temperature in the range 40°C to 60°C were investigated. The temperature affects both the initial hydrolysis rate and the final glucose yield. The highest glucose yield was obtained at 40°C. The yield decreased with increasing temperature, due to increased enzyme deactivation at higher temperatures, while the initial reaction rate increased with increasing temperatures. © 1990.