2.3. Cellulase production
Cellulase was produced by solid-state fermentation according to the method of Xia (Xia and Cen, 1999). Spores of T. reesei ZU-02 were inoculated into the seed medium and incubated at 30 °C for 48 h under aerobic conditions. For solid-state fermentation, 10% liquid seeds were inoculated into the solid medium (5 cm thick) in a 1000 ml Erlenmeyer flask and cultured in an incubator at 28–30 °C for 7 d. Each gram of dry koji contained 146 IU of filter paper activity (FPU) and 12 IU of cellobiase activity (CBU).