Studies about reversibility binding of cellulases to cellulose and biomass

It is known that an increase in the bioethanol production is possible if the efforts are focused on the technologies development to convert the polysaccharides into fermentable sugars. Brazil has a potential for bioethanol production from sugarcane bagasse, which is usually rejected. However, large-scale production is not yet economically viable because, among other reasons, the lignocellulosic structure of sugarcane and sugarcane leaves is not completely understood. The bioconversion of the cellulosic components into fermentable sugars carried out by cellulases, enzymes that are able to perform cellulose depolymerization. These cellulolytic enzymes comprise a group of enzymes that act synergistically to catalyze the hydrolysis of cellulose, but the activity profiles of some enzymes display a singular characteristic: rapid activity decay in the early phase of the hydrolysis. The mechanism behind of this phenomenon has never been fully elucidated, although it represents a major drawback to the industrial application of these enzymes. The activity loss of enzymes has been assigned to it irreversible adsorption into the substrate, even though some reports about the reversibility of this process. For this reason, a detailed description of the adsorption process is required for the fundamental understanding of these important class of industrially enzymes.We have investigated the adsorption reversibility of two cellobiohydrolases and one endoglucanase on four types of pure cellulosic substrates. Surprisingly, we observed that without centrifugation, the results consistently showed full absortion reversibility of enzymes. In contrast, centrifugation and re-suspension of the enzyme-cellulose complex showed extensive irreversibility for all substrates and enzymes.