Cellulase Adsorption during the Hydrolysis of Organosolv- and Organocat-Pretreated Beech Wood
2017
Wang, Yumei | Anders, Nico | Spieß, Antje C.
In a biorefinery, only a complete raw material cellulose saccharification, at high consistencies, leads to high sugar concentrations and thereby to high yields in the subsequent fermentation. However, enzymatic hydrolysis is significantly hampered by a strong slowdown of the reaction after its start, which may be explained, e.g., by enzyme inactivation, inhibition, or compositional and structural changes of the biomass. Effective pulp enzymatic hydrolysis strongly depends on the biomass pretreatment. We studied enzyme adsorption to three cellulosic materials and its effect on the reaction rate during hydrolysis. The maximal cellulase adsorption decreased from 137.7 mg protein/g biomass via 106.1 mg protein/g biomass to 88.8 mg/g biomass for α-cellulose, organocat, and organosolv material, respectively. The initial reaction rates directly correlated to the amount of adsorbed enzyme as predicted by the adsorption isotherms. However, the adsorbed cellulase loading increased dramatically during the reaction and drifted away from the adsorption isotherm. One reason was the changes in substrate composition, e.g., lignin content increased from 22% to 42% for organosolv beech wood during hydrolysis. Most importantly, the cellulases irreversibly adsorbed to the pulp with proceeding hydrolysis, such that they were inactivated.
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