As shown in Fig. 1a, the initial pH of koji was 6.32, then the pH decreased to 6.12 after 24 h of
fermentation. However, it increased to 6.97 at the end of fermentation period. Similar results have also been
reported for A. oryzae in soybean koji by Liang et al. [4]. The increasing of pH of fermented matter was due
to the microbial metabolic activities especially various extracellular proteins production