Undirectional degradation of valonia cellulose microcrystals subjected to cellulase action

AbstractCellulose microcrystals from the alga Valonia macrophysa have been subjected to enzymatic degradation with purified cellulase components from the fungus Trichoderma reesei. Electron microscopy reveals that 1,4-β-D-glucan cellobiohydrolase II erodes only one of the two tips of the microcrystals. This demonstrates not only the exo-action pattern of the enzyme, but also the parallel packing of the cellulose chains within Valonia cellulose microcrystals. When 1,4-β-D-glucan cellobiohydrolase II is mixed with 1,4-β-D-glucan glucanohydrolase II, several sites of attack are observed, located at defects along the microcrystals. In that case again, the biodegradation is persistently unidirectional and visual evidence is given for the endo-exo co-operativity between the two enzymes