Correspondence: Dong Won Kim, Department of Chemistry, College of Natural Sciences, Chungbuk National University, Cheongju 361-763, Korea

Abbreviations: CBH, cellobiohydrolase.

In order to investigate the adsorption behaviour of cellobiohydrolase I in combination with cellobiohydrolase II (CBH I and CBH II) purified from Trichoderma reesei cellulase on Avicel 101, CBH I and II and their various compositions were adsorbed at 5–35 ° C. All adsorptions were found to apparently obey the Langmuir isotherm, and the thermodynamic parameters, DH_a, DS_a and DG_a were calculated from the adsorption equilibrium constant, K_ad. CBH I had a higher adsorption affinity (K_ad) and tightness ( - DH_a) for Avicel than CBH II. This indicates that CBH I showed stronger preferential adsorption than CBH II. The reconstituted CBH I and II mixture showed maximum affinity and tightness at a weight ratio of 1:4. The CBH I and II mixture displayed a significant synergistic degradation of Avicel, with a maximum found at a proportion of CBH I and II of 1:4. The increase of affinity (K_ad) and tightness ( - DH_a) for the adsorption of CBH I combined with CBH II goes in parallel with their maximum synergistic degradation. It indicates that tightness and affinity of adsorption play a crucial role in synergistic degradation of the microcrystalline cellulose. At a specific weight ratio of CBH I and II, the maximum affinity and tightness of these components existed, and the degree of synergism was maximized at this condition. The synergism of two CBHs can be explained by assuming the formation of a partial complex of CBH I and II, which has higher adsorption affinity and tightness than the individual components, and different specificity in the cellulose attack at a specific optimum ratio of CBHs.

Received 4 August 1997/2 October 1997; accepted 10 October 1997

© 1998 The International Union of Biochemistry and Molecular Biology