1. Introduction
The solid-state fermentation (SSF) has been a common method in traditional fermentation. It is
characterized as a fermentation process carried out on a solid medium with low moisture content (aw),typically 0.4-0.9, in nonseptic and natural state. Various agricultural materials such as wheat straw, rice hulls,
and corncobs have been used as substrates for SSF [1].
Koji fermentation is also a kind of SSF system. Koji producing is the first step in making fermented foods
such as soy sauce, miso, mirin and sake [2]. In traditional soy sauce fermentation, soybean has been used as
the protein source for koji. The koji mold (Aspergillus oryzae S.) breaks down carbohydrates and proteins on
soybean to synthesize enzymes. There are various extracellular proteins produced from the culture by A.
oryzae AS 3.951 in soybean koji including leucine aminopeptidase, TAKA-amylase (