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

•Carp egg protein hydrolysates (CEPHs) contained high-quality protein, ω-3 fatty acids, and minerals.•Molecular mass analysis confirmed the presence of low-molecular-mass peptides (6-100 kDa).•We demonstrated the immunomodulatory effects of CEPHs in vivo.•CEPHs stimulated both the humoral and cell-mediated immune responses without allergenicity.•CEPHs could be useful in the food, pharmaceutical, and nutraceutical industries.

ObjectivesThe aim of this study was to prepare protein hydrolysates from underutilized common carp (Cyprinus carpio) egg and to investigate their immunomodulatory effects in vivo.MethodsCommon 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.ResultsThe three hydrolysates contained high protein content (64%-73%) with all essential amino acids, and good proportion of ω-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.ConclusionsThe 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.

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