Abstract
The purified alkaline and neutral proteinases from Aspergillus oryzae dissolved and hydrolyzed soybean proteins to peptides, but produced only small amounts of free amino acids. Peptidases from A. oryzae were found to play an important role in digestion of the peptides formed by the above proteinases to yield free amino acids. Especially, the contribution rate of leucine aminopeptidase II in glutamic acid liberation from soybean proteins was 79.11% under the conditions of the present experiments with the L16-type orthogonal arrangement. A remarkable increase of glutamic acid in the hydrolyzate of the soybean proteins was also exhibited by the action of the above enzyme in the addition tests. On the basis of these results, determinations of activity of some exopeptidases were proposed for better evaluation of shoyu koji.
