EFFECT OF A NONIONIC SURFACTANT ON THE ADSORPTION AND KINETIC MECHANISM FOR THE HYDROLYSIS OF MICROCRYSTALLINE CELLULOSE BY ENDOGLUCANASE-IAND EXOGLUCANASE-II

Effect of a nonionic surfactant, Tween 20 on the adsorption and kineti c mechanism for the hydrolysis of a microcrystalline cellulose, Avicel PH 101, by endoglucanase I (Endo I) and exoglucanase II (Exo II) isol ated from Trichoderma viride were studied. The Langmuir isotherm param eters, amount of maximum adsorption (A(max)) and adsorption equilibriu m constant (K-ad) for the adsorption, were obtained in the presence an d the absence of nonionic surfactant. On the addition of Tween 20, the K-ad and A(max) values of Exo II were decreased, while those of Endo I were not affected. These indicate that the adsorption affinity of Ex o II on the cellulose is weakened by nonionic surfactant, and the surf actant enhanced desorption of Exo II from insoluble substrate. The enz ymatic hydrolysis of the cellulose can be described by two parallel ps eudo-first order reactions using the percentages of easily (C-a) and h ardly (C-b) hydrolyzable cellulose in Avicel PH 101 and associated rat e constants (k(a) and k(b)). The C-a value was increased by adding Twe en 20 for all enzyme samples (Exo II, Endo I and their 1:1 mixture) im plying that the low-ordered crystalline fraction in the cellulose may be partly dispersed by surfactant. The k(a) value was not affect by ad ding Tween 20 for all enzyme samples (Exo II, Endo I and their 1:1 mix ture). The k(b) value of Exo II was increased by adding Tween 20, whil e that of Endo I was not affected. This suggests that the surfactant h elps the Exo II desorb from microcrystalline cellulose, and increase t he hydrolysis rate. These results were show that the increase of hydro lysis of cellulose by the nonionic surfactant is due to both the activ ation of Exo II and partial defibrillation of the cellulose.