ENZYMATIC-HYDROLYSIS OF BACTERIAL CELLULOSE

Native cellulose from the bacterium Acetobacter xylinum as well as aci d-treated bacterial cellulose prepared from partial hydrolysis of the native bacterial cellulose with 2.5 N HCL were subjected to enzymatic hydrolysis by Trichoderma viride cellobiohydrolase I(CBH I) and endogl ucanase II (EG II), The activities of the two enzymes were continuousl y monitored with an oxidation-reduction potential electrode based on t he cellobiose dehydrogenase-ferricyanide redox system. The individual CBH I and EG II hydrolyzed both native and acid-treated bacterial cell uloses in a similar way. While CBH I rapidly hydrolyzed both cellulose samples, the ability of EC II to hydrolyze these samples was very lim ited, However, the hydrolytic behavior of the two cellulose samples by the combination of the two enzymes was significantly different. The r ate of hydrolysis of the native bacterial cellulose increased drastica lly with the combination of the two enzymes, while no synergistic incr ease in hydrolysis rate was observed with the acid-treated cellulose. Electron microscopy demonstrated that the synergistic action of CBH I and EG II for the native bacterial cellulose involved drastic disinteg ration of the twisted and bent ribbon-like structure of microfibril bu ndles and gave rise to the formation of linear, needle-like microcryst allites, Thus, the ribbon-like structure of microfibril bundles in the native bacterial cellulose seems to have a high susceptibility for th e combined action of the two enzymes, In contrast, the microfibril agg regates of the acid-treated bacterial cellulose were not disintegrated by the combination of the two enzymes, From these observations, it se ems reasonable to assume that differences in the assembling pattern of the microfibrils must be one of the major reasons for the significant differences in the synergism of the two enzymes for the two bacterial cellulose samples. (C) 1998 Elsevier Science Ltd.