Soybean were soaked in water for 6-8 h then autoclaved at 121 °C for 40 min. Wheat bran was roasted to dark brown and cracked then 32% of total wheat bran was ground to powder and mixed with culture before spreading to raw material to ensure through mixing of raw material. Different combinations of soybean and wheat bran (40%:60%, 50%:50%, and 60%:40% w/w) inoculated with 0.1% of culture spore were used as substrates for koji fermentation and incubated at 30°C for 72 h. Spores of A. oryzae S. NPUST-FS-206-A1 in 2 inoculum sizes (0.1% and 0.3% w/w) were inoculated into the raw material.