Silver carp (Hypophthalmichthys molitrix) by-product hydrolysates: A new nitrogen source for Bifidobacterium animalis ssp. lactis BB-12.

Appropriate utilization of silver carp by-products is critical for enhancing industry profit and sustainability of aquaculture. This study explored the effect of the silver carp by-product hydrolysates on the growth of Bifidobacterium animalis ssp. lactis BB-12. Results indicated that papain recovered more nitrogen and < 1 kDa components from silver carp by-products than neutrase and alcalase. Papain-2 h (by-products hydrolyzed by papain for 2 hrs) was more effective in promoting the growth of BB-12. The content of < 1 kDa components, sulfhydryl-containing amino acids, and peptides composed of all the hydrophobic amino acids in hydrolysates was positively correlated to the growth of BB-12. BB-12 cultured by papain-2 h substituted medium exhibited a thinner and shorter morphology at 4 hrs of cultivation. This study provided a new nitrogen source for Bifidobacterium animalis ssp. lactis BB-12 and possible strategy for converting by-products to reduce aquacultural waste.