Probiotic potential of autochthonous Enterobacter mori ASP8 and Bacillus stercoris ASP10 isolated from gut microbiota of healthy stinging catfish, Heteropneustes fossilis (Bloch).

This study characterizes two bacterial isolates Enterobacter mori ASP8 and Bacillus stercoris ASP10, derived from the stinging catfish (Heteropneustes fossilis) and evaluates in vitro probiotic efficacy for enhancing sustainability in freshwater aquaculture. Rigorous biosafety assessments confirmed that both strains were non-hemolytic, were non-blood coagulant, lack DNase/RNase activity, and were non-biogenic amine producers. Both isolates exhibited high gastrointestinal resilience and survival under stimulated stomach duodenum passage (SSDP) with a value of 81.98% for E. mori ASP8 and 84.89% for B. stercoris ASP10. The isolates also showed strong tolerance to bile, phenol, and lysozyme. Functional assays revealed robust hydrocarbon adherence up to 84.83% and significant co-aggregation with fish pathogens varied between 50.5 and 72.69%. Notably, it was found that B. stercoris ASP10 exhibited biofilm-forming capabilities on Congo red agar. E. mori ASP8 and B. stercoris ASP10 showed strong antibacterial activity against seven pathogens by producing bacteriocin, siderophore production. In addition, the isolates exhibited cholesterol lowering, antioxidant potentially and multi-enzymatic (amylase, protease, cellulase, and lipase) activities. Overall findings concluded both strains are effective, but B. stercoris ASP10 emerged as superior probiotic candidate for future aquaculture application.