The initial pHs of different treatments were all around pH 6.32, then the pH decreased followed by an increasing after 36 h of fermentation (Fig. 1a). The results showed that the koji sample containing 60% soybean presented the highest increasing of pH to 6.97 after 72 h of cultivation. The increasing of pH was due to the production of various extracellular proteins from A. oryzae S. during soybean koji fermentation [3].