with different cellulase loadings (1.5, 3.7, 7.5, 11.2, 14.9, 22.4, and 29.9 FPU/cellulose) in 10 mL of 0.1 M citrate buffer (pH 4.8) supplemented with 80 lg/mL tetracycline and 60 lg/mL nystatin (dissolved in DMSO) to prevent microbial contamination