Chemical composition and immunomodulatory effects of enzymatic protein hydrolysates from common carp (Cyprinus carpio) egg

Objectives: The aim of this study was to prepare protein hydrolysates from underutilized common carp (Cyprinus coupio) egg and to investigate their immunomodulatory effects in vivo. Methods: Common carp (Cyprinus carpio) egg (roe) was hydrolysed by pepsin, trypsin, and Alcalase. Chemical composition (proximate, amino acid, mineral and fatty acid compositions) and molecular mass distribution of the three hydrolysates were determined. The carp egg protein hydrolysates (CEPHs) were evaluated for their immunomodulatory effects in BALB/c mice. CEPHs (0.25, 0.5 and 1 g/kg body weight) were orally administered daily to female BALB/c mice (4-6 wk, 18-20 g) for a period of 45 d. After 45 d, mice were sacrificed and different tissues were collected for the immunologic investigations. Results: The three hydrolysates contained high protein content (64%-73%) with all essential amino acids, and good proportion of omega-3 fatty acids, especially docosahexaenoic acid. Molecular mass analysis of hydrolysates confirmed the conversion of large-molecular-weight roe proteins into peptides of different sizes (5-90 kDa). The three hydrolysates significantly enhanced the proliferation of spleen lymphocytes. Pepsin hydrolysate (0.5 g/kg body weight) significantly increased the splenic natural killer cell cytotoxicity, mucosal immunity (secretory immunoglobulin A) in the gut and level of serum immunoglobulin A. Whereas Alcalase hydrolysate induced significant increases in the percentages of CD4+ and CD8+ cells in spleen. Conclusions: The results demonstrate that CEPHs are able to improve the immune system and further reveal that different CEPHs may exert differential influences on the immune function. These results indicate that CEPHs could be useful for several applications in the health food, pharmaceutical, and nutraceutical industries. (C) 2015 Elsevier Inc. All rights reserved.