The role of product inhibition as a yield-determining factor in enzymatic high-solid hydrolysis of pretreated corn stover.

Industrially, enzymatic hydrolysis of lignocellulose at high solid content is preferable over low solids due to a reduction in processing costs. Unfortunately, the economic benefits are counteracted by a linear decrease in yield with solid content, referred to as the "solid effect" in the literature. In the current study, we investigate the contribution of product inhibition to the solid effect (7-33 % solids). Product inhibition was measured directly by adding glucose to high-solid hydrolysis samples and indirectly through variation of water content and beta-glucosidase concentration. The results suggest that the solid effect is mainly controlled by product inhibition under the given experimental conditions (washed pretreated corn stover as substrate). Cellobiose was found to be approximately 15 times more inhibitory than glucose on a molar scale. However, considering that glucose concentrations are at least 100 times higher than cellobiose concentrations under industrial conditions, glucose inhibition of cellulases is suggested to be the main cause of the solid effect.