Abstract: In order to prepare a heme-rich polypeptide product, mixed papain and neutral protease were used for the hydrolysis of porcine hemoglobin. The effects of substrate concentration, mixing ratio for papain and neutral protease, hydrolysis pH and hydrolysis temperature on hydrolysis degree, protein recovery rate and heme content were investigated. The results indicated that substrate concentration was the most important factor that affects hydrolysis degree and protein recovery rate. pH was the most important factor that affects heme content. The optimal hydrolysis conditions for the preparation of heme-rich polypeptide products were substrate concentration of 6%, pH 8, hydrolysis temperature of 55 ℃ and papain-to-neutral protease ratio of 5:5. Under the optimal preparation conditions, relatively high protein recovery rate and heme content for the hydrolysis of porcine hemoglobin were achieved.

Key words: porcine hemoglobin, heme, polypeptide, enzyme complex, hydrolysis