ELECTRON-MICROSCOPIC OBSERVATIONS OF CELLULOSE MICROFIBRIL DEGRADATION BY ENDOCELLULASE FROM TRICHODERMA-REESEI

Structural changes of crystalline cellulose microfibrils, as induced by the addition of endocellulase (EC 3.2.1.4), were followed by transmission electron microscopy (TEM). Crystalline monofibrous cellulose was prepared from Sinapis alba L. plant seed slime. Endoglucanase, with a molecular mass of 25 kDa, was purified to homogeneity by affinity chromatography followed by preparative isoelectric focusing of Trichoderma reesei culture fluids. The structural effect of endoglucanase on Sinapsis cellulose was visualized by means of a platinum-shadowed specimen with TEM. Endoglucanase eroded the microfibril periphery by splitting it into subfibrils. Subfibrils had one free end but remained integrated in the microfibril. With a longer period of endoglucanase action, the microfibril surface was completely splayed into subfibrils to appear as a whisker-like microfibril periphery.