The activity profile of a 1:0.30 mixture of Celluclast 1.5 L FG and Novozym 188 (Novozymes) was investigated using Whatman #1 filter paper (W1FP) as a single substrate for hydrolysis. The procedure was based on the ability of the enzymes to release total (RSTot), insoluble (RSInsol) and soluble (RSSol) reducing sugars from W1FP. RSInsol was used to estimate endoglucanase (EnG) activity whereas exoglucanases (ExG) were assessed by measuring RSSol in the presence of delta-gluconolactone. Finally, the beta-glucosidase (beta G) activity was derived from the difference between RSSol measurements in the presence and absence of delta-gluconolactone. When this analytical procedure was applied to W1FP using 9.64 mg mL(-1) of the enzyme mixture, the relative contributions of EnG, ExG and beta G to the total cellulase activity were 63.28%, 12.02% and 24.70%, respectively. Also, this ratio changed with changes in the enzyme loading, giving a new insight into the synergy that exists among the enzymes. (C) 2013 Elsevier Ltd. All rights reserved.