Impact of down-stream processing of bakers yeast (Saccharomyses cerevisiae) on immune responses in Atlantic salmon (Salmo salar)

Abstract

Probiotics have been using in human as well as other animals as food supplements for improved health status and disease resistance. The present study was designed to evaluate the probiotic mediated health status improvement by a candidate probiotic bacterium Paenibacillus polymyxa HGA4C in a teleost fish Oreochromis niloticus. The investigation revealed that the fish supplemented with two levels of the probiotic bacterium (1 × 106 and 1 × 108 CFU g−1) significantly (P < 0.05) improved morphometric parameters such as final weight, weight gain and feed conversion ratio. The specific growth rate was significantly increased (1.58 ± 0.23) only in the group supplemented with 1 × 108 CFU g−1. The hepato-somatic index in the control and treatment groups was not significantly different. The bacterium improved the digestive capacity of the fish by increasing lipase, amylase and protease enzymes. The antioxidant status in the liver and intestinal tissues was enhanced by the bacterium. Probiotic supplementation effectively modulated the expressions of growth hormone binding receptor genes such as GHR-1 and GHR-2, insulin-like growth factors (IGF-1) and IGF-2 genes in the fish. Furthermore, the probiotic bacterium upregulated Toll-like receptor (TLR-2) gene expression and anti-inflammatory cytokine (IL-10) in the intestinal tissue of the fish. Intestinal MUC 2 up-regulation by the bacterium has indicated the mucosal remodeling of the host fish. All these results have shown that the probiotic bacterium could improve the feed utilization, feed conversion, antioxidant capacity, and immunity of Oreochromis niloticus.