Efficacy of Rhodobacter sphaeroides TISTR 1529 on the growth performance, immune response, and amino acid profile of Pacific whiteleg shrimp, Penaeus vannamei

Abstract

Photosynthetic bacteria have been used as probiotics for decades, and are notable for their ability to produce 5-aminolevulinic acid (ALA), a precursor of glutamic acid, and to synthesise astaxanthin, a potent carotenoid antioxidant. Enhancing shrimp to be both palatable and health-beneficial presents a significant challenge. In this study, Pacific whiteleg shrimp (initial weight 6.8 ± 0.14 g) were fed diets supplemented with different concentrations of Rhodobacter sphaeroides (1 × 106 (Wang and Gu, 2010), 1 × 107 (Chumpol et al., 2017), and 1 × 108 CFU/mL) for 14 days, followed by a Vibrio parahaemolyticus challenge. Treated groups showed significantly improved growth performance, with T2 and T3 achieving the highest average daily gain (0.143 ± 0.02 g and 0.142 ± 0.01 g, respectively). Enhanced immune responses were observed through increased hemocyte counts and upregulation of immune-related genes (ALF, crustin, penaeidin3). Notably, all treated groups demonstrated significantly higher survival rates post-challenge, with T4 achieving 86.67 % survival compared to 28.33 % in the control group. Additional benefits included increased astaxanthin content and elevated levels of aspartic and glutamic acids in treated groups, suggesting potential improvements in both shrimp health and product quality. In conclusion, this study demonstrates that photosynthetic bacteria can enhance growth performance, immune response, and the amino acid profile in P. vannamei, offering a potentially healthier option for consumers.