Suggested improvements to the standard filter paper assay used to measure cellulase activity

Two suggestions can be found in the literature to improve the reproducibility of the Mandels' filter paper assay: add supplemental cellobiase and increase the boiling time for color development. Here we provide data that strongly supports adding supplemental cellobiase. Adding supplemental cellobiase increased assay response by 56%. Cellulases from different sources have different cellobiase activities, which would cause significant variation in the assay response. There is no need for additional boiling time—5 minutes is sufficient. For maximum reproducibility, it is essential that the water bath vigorously boil so that temperature excursions are minimized.