RESUMO
This study describes a procedure for the selective determination of endo- (EG) and exo- (ExG) cellulase activities using filter paper as the sole substrate. The procedure is based on the enzymes mode of action whereby EG activity predominantly forms insoluble reducing sugars and ExG activity soluble reducing sugars. The procedure was developed using filter paper as substrate for hydrolysis with three cellulase preparations of Hypocrea jecorina containing either endoglucanase (EG), predominantly exoglucanase (ExG) or both endo- and exoglucanase activities. Hydrolysis experiments, which were followed assessing the formation of total, soluble and insoluble reducing sugars (RS), showed that up to 30 min of hydrolysis predominantly insoluble reducing sugars were formed, while after this initial hydrolysis stage soluble reducing sugar formation increased significantly, making it thus possible to measure separately EG and ExG activity. FPA activities obtained from the reaction products at different reaction times suggest that EG-activity (FPA(insol)) should be measured between 10 and 20 min of hydrolysis. The proposed procedure allows to evaluate the EG and ExG activity contribution to total cellulase activity and to calculate the endo/exo activity ratio of any cellulase preparation.
