Measuring cellulase activity: application of the filter paper assay to low-activity enzyme preparations.

An approach is presented for obtaining relative filter paper activities for enzyme preparations having activities below that required for application of the traditional International Union of Pure and Applied Chemistry filter paper assay. The approach involves the utilization of protein stabilizers to retard the time-dependent enzyme inactivation that may occur under traditional filter paper assay conditions. Enzyme stabilization allows extended reaction times and the calculation of relative activities based on the time required for saccharification of 3.6% of the traditional substrate, making results proportional to those obtained in the traditional International Union of Pure and Applied Chemistry assay. The assay is demonstrated using a commercial cellulase preparation along with KCl and bovine serum albumin as protein stabilizers.