Reactivities of cellulases from fungi towards ribbon-type bacterial cellulose and band-shaped bacterial cellulose

We have investigated the reactivities of various cellulases on ribbon-type bacterial cellulose (BC I) and band-shaped bacterial cellulose (BC II) so as to clarify the properties of different cellulases. BC I was effectively hydrolyzed by exo-type cellulases from different fungi from twice to four times as much as BC II, but endo-type cellulases showed little difference in reactivity on those substrates. One of the endo-type cellulases, EG II from Trichoderma reesei, degraded BC II more rapidly than exo-type cellulases even in the production of reducing sugars. The degree of polymerization (DP) of BC II was rapidly decreased by endo-type cellulases at an early stage, while exo-type cellulases did not cause the decrease of DP at the initial stage, though the decrease of DP was observed after an incubation of 24 h. All exo-type cellulases adsorbed on BC I and BC II, while endo-type cellulases except for EG II adsorbed slightly on both substrates. It was interesting to observe EG II adsorbed on BC I but not on BC II. It is suggested that the adsorption of enzyme on cellulose is important for the degradation of BC I, but not for BC II. It is proposed that the ratio of a specific activity of each enzyme between BC I and BC II represents the difference in the mode of action of cellulase. Furthermore, the K-RW value, which we can calculate from the decrease of DP/reducing sugar produced, is effective for discriminating the mode of action of cellulase, especially the evaluation of randomness in the hydrolysis of cellulose by endo- and exo-type cellulases.