Identification of Inhibitory Compounds to Endo-cellulase and β-glucosidase by Switchgrass Dilute Acid Prehydrolysates

Degradation compounds released during dilute acid pretreatment of lignocellulosic biomass can be inhibitory to enzyme used for cellulosic saccharification. However, it is not clear which compounds or combinations of compounds released during dilute acid pretreatment are the most detrimental. Moreover, the formation of those byproducts is strongly dependent on the pretreatment conditions, making their identification extremely challenging. This current work attempts to relate composition of dilute acid prehydrolysates to the inhibition of endo-cellulase and β-glucosidase by the liquid prehydrolysates. Liquid prehydrolysates were obtained from pretreatment of switchgrass with 0.5 and 1%  (v/v) sulfuric acid at 140°C, 160°C, and 180°C for 10, 20, 30, and 40 min. Inhibition of endo-cellulase and β-glucosidase were studied, respectively, with Cellazyme T and cellobiose as substrates. Analysis of the liquid prehydrolysates showed that composition profiles of prehydrolysates are dependent on pretreatment conditions. Activities of both enzyme systems were significantly reduced by almost all the liquid prehydrolysates. Reduction of enzyme activity was also dependent on pretreatment conditions and composition profile of liquid prehydrolysates.