Adsorption kinetics and behaviour of two cellobiohydrolases from Trichoderma reesei on microcrystalline cellulose

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 degrees C. All adsorptions were found to apparently obey the Langmuir isotherm, and the thermodynamic parameters, Delta H-a, Delta S-a and Delta G(a) were calculated from the adsorption equilibrium constant, K-ad. CBH I had a higher adsorption affinity (K-ad) and tightness (-Delta H-a) for Avicel than CBH II. This indicates that CBH I showed stronger preferential adsorption than CBH II. The reconstituted CBH I and If 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 (-Delta H-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.