CELLOBIOSE DEHYDROGENASE, AN ACTIVE AGENT IN CELLULOSE DEPOLYMERIZATION

The ability of cellobiose dehydrogenase purified from Phanerochaete ch rysosporium to modify a Douglas fir kraft pulp was assessed. Although the addition of cellobiose dehydrogenase alone had little effect, supp lementation with cellobiose and iron resulted in a substantial reducti on in the degree of polymerization of the pulp cellulose. When the rea ction was monitored over time, a progressive depolymerization of the c ellulose was apparent with the concomitant production of cellobiono-1, 5-lactone. Analysis of the reaction filtrates indicated that glucose a nd arabinose were the only neutral sugars generated. These sugars are derived from the degradation of the cellobiose rather than resulting f rom modifications of the pulp, These results suggest that the action o f cellobiose dehydrogenase results in the generation of hydroxyl radic als via Fenton's chemistry which subsequently results in the depolymer ization of cellulose. This appears to be the mechanism whereby a subst antial reduction in the degree of polymerization of the cellulose can be achieved without a significant release of sugar.