Abstract:

In this study, eggshell membrane was used as the raw material to prepare polypeptides by enzymatic hydrolysis. In order to maximize degree of hydrolysis (DH) and nitrogen yield, the optimal hydrolysis mode of eggshell membrane was selected from hydrolysis with pairwise combination (used sequentially or simultaneously) of alkaline protease, papaya protease and trypsin that resulted in higher degree of hydrolysis and nitrogen yield than neutral protease and pepsin, or each of them. Meanwhile, based on this, the optimal values of crucial technological parameters, including temperature, hydrolysis time, pH and total enzyme dose, were determined by the method of quadratic orthogonal rotation combination design. Results showed that the optimal enzymatic production process was based on sequential hydrolysis at 50 ℃ with alkaline protease for 2 h at pH 9.0 followed by papaya protease for 1 h at pH 5.5 using a mixture of alkaline protease and papaya protease at 8:2 activity ratio with 16000 U/g total enzyme dose, which gave 46.12% DH and 85.56% nitrogen yield.

Key words: soluble eggshell membrane protein (SEP), composite enzymatic hydrolysis, polypeptides, quadratic orthogonal rotation combination design