Dietary Probiotic Bacillus subtilis AAHM-BS2360 and Its Postbiotic Metabolites Enhance Growth, Immunity, and Resistance to Edwardsiellosis in Pangasianodon hypophthalmus
Nugroho Wiratama, Pakapon Meachasompop, Benchawan Kumwan, Yosapon Adisornprasert, Prapansak Srisapoome, Phornphan Phrompanya, Patcharapong Thangsunan, Pattanapong Thangsunan, Kanokporn Saenphet, Supap Saenphet, Wararut Buncharoen, Anurak Uchuwittayakul
Abstract
Edwardsiellosis, caused by Edwardsiella tarda, poses a significant threat to the aquaculture industry, particularly in pangasius farming. This study investigates the effects of probiotic Bacillus subtilis AAHM-BS2360 and its postbiotic metabolites on growth performance, immune responses, antioxidative activity, and disease resistance against E. tarda infection. A total of 240 healthy pangasius (37.0 ± 4.9 g) were divided into four treatment groups with four replicate tanks each, as follows: (1) the Control group, which received feed top-dressed with 100 mL of 0.85% NaCl/kg diet; (2) the Probiotic group, which received feed supplemented with 100 mL of B. subtilis AAHM-BS2360 cells at the concentration of 1 × 1012 CFU/kg diet; (3) the Postbiotic group, which received feed supplemented with B. subtilis AAHM-BS2360 cell-free supernatant 100 mL/kg diet; and (4) the Pro + Post group, which received a combination of B. subtilis AAHM-BS2360 cells and cell-free supernatant. After 30 days of feeding treatment, biochemical serum analysis revealed a significant increase in the AST/ALT ratio in the Postbiotic group. The Probiotic and Postbiotic treatments increased lysozyme activity in mucus, indicating an innate immune response to pathogens. The Pro + Post group exhibited the highest levels of catalase (CAT) in serum and upregulated antioxidant-related genes. All treatment groups receiving B. subtilis AAHM-BS2360, metabolites, and their combinations showed significant upregulation of immune-related genes, like lygl1, tgfb, b2ml, and tnf. The expression of proinflammatory genes (litaf, ifngr1l, c3, il13, and il1b) increased, with the most pronounced effects observed in the Pro + Post group. The Probiotic group showed significant upregulation of the growth-related gene igf1. Meanwhile, the Pro + Post group showed significantly higher values in SGR and ADG parameters, with values of 3.29 ± 0.98%/day and 1.42 ± 0.52 g/day respectively (p < 0.05). Survival rates were significantly higher in the Pro + Post (87.5%), Postbiotic (84.37%), and Probiotic (81.25%) groups when challenged with E. tarda. Dietary supplementation with B. subtilis AAHM-BS2360, its metabolites, and their combination enhanced immune response, reduced oxidative stress, and improved growth performance in pangasius, highlighting its potential as a functional feed additive for sustainable aquaculture.