Optimization of Dilute Acid Pretreatment of Biomass

Lignocellulosic biomass in its native form is quite resistant to enzymatic attack. We have, therefore, investigated the kinetic parameters of the pretreatment of wheat straw and aspen wood, catalyzed by 0. 5% sulfuric acid at a pH of 1. 5 and a temperature range between 95 and 160 degree C. The results clearly indicate that removal of hemicelluloses by pretreatment is a necessary prerequisite for high enzymatic digestibility of cellulose for the two biomass substrates investigated. Lignin removal does not seem to be necessary. Kinetic data on hydrolysis of xylan backbones in wheat straw and aspen hemicelluloses indicate that two fractions of xylan bonds exist at lower temperatures (95-140 degree C) which vary greatly in rate and activation energy during dilute acid hydrolysis.