The results showed different degrees of improvement in the protease activity of the four transformants when compared with wild-type A. oryzae. A major improvement in the polypeptide yield was achieved when these strains were used in soybean mealfermentation. The polypeptide conversion rate of one of the four transformants, A. oryzae pep, reached 35.9%, which was approximately twofold higher than that exhibited by wild-type A. oryzae. Amino acid content analysis showed that the essential amino acid content and amino acid composition of the fermentation product significantly improved when engineered A. oryzae strains were used for soybean mealfermentation.
Conclusions:
These findings suggest that cloning of microbial proteasegenes with good physicochemical properties and expressing them in an ideal host such as A. oryzae is a novel strategy to enhance the value of soybean meal.