Adsorption and activity profiles of cellulases during the hydrolysis of two Douglas fir pulps

The adsorption and specific activities of various cellulases were evaluated during the hydrolysis of Avicel and Douglas fir-derived kraft and refiner mechanical pulps (RMP). Both the RMP and kraft pulps required higher enzyme loadings and longer hydrolysis times to achieve complete hydrolysis than d id Avicel. Complete hydrolysis of a 2% kraft pulp required an enzyme loadin g of 60 FPU g(-1) cellulose while loadings as high as 750 FPU g(-1) cellula se did not result in complete hydrolysis of the RMP. Almost all of the prot ein originally added to the Avicel could be recovered in solution after com plete hydrolysis of the substrate; however, only 50% of the initially added protein (40 FPU g(-1) cellulose) was recovered from the two pulps after 72 h incubation. During the hydrolysis of all three substrates, a change in t he specific enzyme activities and ratios in the reaction filtrate were obse rved when compared to the initial enzyme preparation. The xylanase and endo glucanase activities were more closely associated to the recalcitrant Avice l residue while these activities were preferentially released into solution during hydrolysis of the kraft pulp. There was no significant difference i n the distribution of the enzyme activities during the hydrolysis of the RM P. For all of the substrates, the filter paper activity was tightly associa ted with the insoluble fraction throughout the reaction. (C) 1998 Elsevier Science Inc.