s Cell Wall Components of Bacillus pumilus SE5 Improved the Growth, Digestive and Immunity of Grouper (Epinephelus coioides)

Background: Probiotic cellular components could be an interesting alternative to live probiotics, which could potentially cause safety problems in open aquatic environments. Objective: The cell wall (CW), peptidoglycan (PG) and lipoteichoic (LTA) were extracted from probiotic strain of Bacillus pumilus SE5, and these biomolecules were used to develop the possible application in fish aquaculture. Methods: Grouper (Epinephelus coioides) juveniles were fed with either a basal control diet or the basal diet supplemented with CW, PG and LTA respectively for 60 days, and the growth performance, digestive enzymes activities, serum immune responses and immune genes expression in head kidney were determined. Results: Dietary supplement PG and LTA significantly improved final body weight (FBW), weight gain rate (WGR), specific growth rate (SGR) and protein efficiency ratio (PER), while significantly decreased feed conversion ratio (FCR) was noticed in all the treatments compared with the control group. Dietary supplements of CW, PG and LTA enhanced the activities of trypsin, lipase and amylase in the liver. Serum complement C3 and IgM levels as well as, AKP, ACP and SOD activities elevated significantly in fish fed the PG and LTA containing diets. Furthermore, PG and LTA containing diets, significantly up-regulated expression of TLR2, NOD2, IL-8, IgM and three antibacterial peptides genes (epinecidin-1, hepcidin-1 and β-defensin) in the head kidney. Conclusion: PG and LTA originated from probiotic B. pumilus SE5 could effectively enhance the growth performance, feed utilization, digestive ability and boost innate and adaptive immune system of E. coioides.