Proteolytic enzymes are important to modify the processing characteristic of soybeans and have been utilized for the production of soybean-derived foods-e.g., miso and soy sauce. Proteolytic enzymes produced in the cotyledons of soybean seeds during germination are used to modify the characteristics of processed foods. The optimum conditions for protease production during germination were determined and the characteristics of these proteases were described. The soybean variety Ohtsuru produced high levels of a semi-alkaline proteolytic enzyme under conditions of 20% CO₂ and 25℃. The protease was purified using cation-exchange and size-exclusion chromatography. The monomeric protein had a mass of 84.9 kDa. The optimum pH and temperature for this protein were pH8.0 and 30℃, respectively, and the protein was stable at pH7.0-10.0 and 4-30℃. The proteolytic enzyme was activated by magnesium, zinc, and manganese ions and was inhibited by copper and mercury ions, EDTA, and EGTA. However, the enzyme was not inhibited by trypsin inhibitor. The enzyme cleaved substrates by endo-type proteolysis and cleaved the α-, α'-, and β-subunits of the soy protein β-conglycinin. The enzyme was able to modify the characteristics of soybean during their production. Moreover, it digested a major allergen protein, Gly m Bd60K, which is an α-subunit of beta-conglycinin.

　Spoilage of cooked rice occurred as a result of heat insulation. The cooked rice had an off-flavor that was caused by spoilage. This phenomenon is thought to be caused by microorganisms. Therefore, in this study, we attempted to isolate the contaminating microorganisms from cooked rice and identify them by using polymerase chain reaction (PCR) and PCR-denaturing gradient gel electrophoresis (DGGE). No microorganisms were detected in normal cooked rice; however, microorganisms were detected at 4.6×10⁶ cfu/g in rice spoiled by 72h of heat insulation. The isolates were able to grow at 60～65℃ on the cooked rice, and they produced an off-flavor. Based on phylogenetic analysis, the isolates were identified as members of the genus Geobacillus, and were closely related to Geobacillus thermoleovorans. Contaminating microorganisms in the cooked rice were identified by PCR using bacterial universal primers and G. thermoleovorans was only detected using PCR-DGGE. These results suggest that G. thermoleovorans was the contaminating microorganism in the spoiled cooked rice and produced the off-flavor.