In order to produce raw soy sauce, a mixed culture of 3,600 kg defatted soybean, 3,600 kg wheat grain, and 3.8 kg mixed tane-koji was prepared with Aspergillus oryzae K2 (length of conidiophores, about 350 mu m) and a late-conidiating strain, A. oryzae HG (length of conidiophores, about 2,500 mu m). The resulting mixed culture showed high glutaminase activity (5.5 units/g dry koji) compared with a monoculture of strain K2 (1.8 units/g dry koji). In addition, the number of conidia contained in the mixed culture (2.5 x 10(7)/g dry koji) drastically decreased compared with those in the monoculture of strain K2 (1.3 x 10(8)/g dry koji), thus resolving the serious problem of conidia dust contaminating the working environment during the koji-making process. The mixed culture was then combined with 13,000 l of 23% NaCl solution and fermented for 180 d. The glutamic acid content of the raw soy sauce made with mixed culture was 1.25 times higher than that of the raw soy sauce made by the conventional soy sauce making process.