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Study of kinetics of enzymatic hydrolysis of cellulose materials

Michael Ioelovich

In this paper, the kinetics of enzymatic hydrolysis of cellulose samples with different structural characteristics has been studied using the equation of Avrami-Kolmogarov-Erofeev (AKE): ln(1- á) = -K tn, where á is conversion degree; K is effective rate constant; t is time, and n is effective order of the kinetic process. It was shown thatAKE-equation adequately describes the experimental kinetic curves. In case of hydrolysis of highly crystalline microcrystalline cellulose, the coefficient n in the AKE-equation is 0.5, which is typical for diffusion mechanismof the process.With the decrease of crystallinity degree of cellulose, the coefficient n increases and reaches 1 for completely amorphous cellulose in awet state that indicates on the reaction of first-order. The intermediate n-value from 0.5 to 1 shows that the enzymatic hydrolysis of the sample is limited by diffusion of the large enzymemolecules into the cellulose structure. Drying of cellulose samples causes a decrease of pore volume and amplifies the contribution of diffusion to integral hydrolysis process. Effective rate constant K of enzymatic hydrolysis also increases with decreasing of crystallinity of the cellulose sample. Furthermore, the K-value for the wet sample was higher than for the dry sample. The use of parameters ofAKE-equation allows predicting the kinetics of cellulose conversion into glucose during enzymatic hydrolysis