A STUDY OF ENZYME ADSORPTION AND REACTION KINETICS FOR CELLULOSE HYDROLYSIS
Abstract
Enzymatic hydrolysis of cellulose occurs due to the combined catalytic action of two types of cellulase components commonly referred to as C(,1) and C(,x). However, before the hydrolysis reaction can begin, it is necessary for these enzymes to first adsorb onto the accessible surfaces of the insoluble cellulose substrate. The objective of the study was to gain a better understanding of the relationships between the adsorption of these enzyme components, the hydrolysis kinetics, the cellulosic surface area accessible to the enzymes, and the cellulose crystallinity. These relationships were investigated by passing a Trichoderma viride cellulase solution through columns of cellulose powder having different accessibility and crystallinity, and then analyzing the quantities of the different enzyme components and the hydrolysis product in the effluent. The amounts of the different cellulase components were analyzed using high-performance anion-exchange chromatography. Additional adsorption and hydrolysis experiments were done using columns of cellulose beads specially developed to provide a model substrate for this analysis. A good comparison was observed between the amount of protein adsorbed onto the external surface of these cellulose beads and the bead capacity as calculated by assuming smooth beads, monolayer adsorption, and reasonable values for the size and molecular weight of the cellulase protein. A mathematical model has been formulated to describe the kinetics of enzyme adsorption and the resultant, initial hydrolysis rate in cellulose column. The analytical solutions obtained have been linearized into a convenient form so that the kinetic parameters of the model can be readily determined from experimental breakthrough curves. Using this model, a linear relationship was observed between the rate of reducing sugar production and the amount of cellulase adsorbed onto a cellulose bead column. A linear relationship, however, was not observed for the experiments using columns of cellulose powder. The effect of axial dispersion on this analysis was evaluated with a numerical program (using parameters obtained from experiment) and influence of dispersion was found to be negligible.
Degree
Ph.D.
Subject Area
Chemical engineering
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