Immune stimulant effects of a nucleotide-rich baker's yeast extract in the kuruma shrimp, Marsupenaeus japonicus

Immune stimulant effects of a nucleotide-rich baker's yeast extract (Vertex IG20) were investigated in the kuruma shrimp, Marsupenaeus japonicus by examining expression of anti-microbial peptides/proteins (AMPs) such as penaeidin (MjPen), crustin (MjCrus) and lysozyme (MjLyz) genes. Furthermore, to confirm that the baker's yeast extract-induced AMPs were functional, we also assessed the effect of its oral administration on resistance to Vibrio nigripulchritudo infection in the kuruma shrimp. Our results demonstrate that baker's yeast extract-injected and fed shrimps displayed a significant up-regulation of MjPen, MjCrus and MjLyz gene expression in the lymphoid organ. Moreover, significantly increased (P < 0.01) resistance to the bacterial pathogen in term of better post infection survival (66.6%) was observed in the shrimp fed with the yeast extract-incorporated diet compared with the control diet fed group (8.3%). The present study indicates the immunostimulatory effects of the nucleotide-rich baker's yeast extract on the kuruma shrimp immune system and supports its potential use in aquaculture.

► Baker's yeast extract contained 36.7% nucleotides. ► Baker's yeast extract-treated shrimp displayed higher expression of immune genes. ► Yeast extract fed shrimp showed increased pathogen resistance. ► Baker's yeast extract had immunostimulatory effects on kuruma shrimp immune system. ► It may be used as a potential immunostimulant in shrimp aquaculture.