Digestion of pretreated aspen substrates.

Considerable controversy exists concerning the role lignin plays in the adsorption of cellulase enzymes on biomass. Recent studies using extracted, purified hardwood lignin have shown these materials have a propensity for cellulase adsorption; however, native lignin is carbohydrate-linked and far less condensed. In this study, we report the results of adsorption-kinetics analyses of cellulase-complex activities using five pretreated aspen substrates, including an exhaustively enzyme-hydrolyzed one. These data indicate that the polymer-binding cellulase activities are removed from solution at higher rates and extents in the presence of low lignin-content versus high lignin-content substrates. This order of adsorption was found to be essentially the inverse for beta-glucosidase adsorption. [ABSTRACT FROM AUTHOR]