Wheat gluten hydrolysis using isolated Flavourzyme peptidases: Product inhibition and determination of synergistic effects using response surface methodology

Abstract

The commercial peptidase preparation Flavourzyme is derived from the Aspergillus oryzae strain ATCC 42149/RIB 40 (Yellow koji mold) and is widely used for protein hydrolysis in various industrial and research applications. However, a biochemical characterization of the Flavourzyme peptidases is difficult, because obtaining purified proteins is essential when functional and structural characterization studies are targeted. Key enzyme activities (three endopeptidases, two aminopeptidases, two dipeptidyl peptidases) have recently been identified and isolated from this commercially available enzyme preparation. The impact and the synergism of theses peptidases on the complex wheat gluten hydrolysis are yet unclear. However, the knowledge about the latter is crucial for an efficient protein hydrolysis. In the present study, we determined the product inhibition for the seven isolated peptidases and analyzed the impact of each peptidase on the wheat gluten hydrolysis using response surface methodology. In general, both aminopeptidases and the three endopeptidases were of major importance. One of the endopeptidases (alkaline protease 1) was least affected by product inhibition and showed the highest effect on the wheat gluten hydrolysis. In the case of the aminopeptidases, the leucine aminopeptidase 2 showed a higher impact on the hydrolysis compared to the leucine aminopeptidase A, but exhibited the highest product inhibition sensitivity. The dipeptidyl peptidases were of only minor impact on the wheat gluten hydrolysis. To conclude, six out of the seven peptidases contributed significantly (p<0.05) to the wheat gluten hydrolysis and should be considered when designing such a process.