Potential enzyme-producing probiotic from Channa striata for enhancing growth, digestive enzyme activity, and antioxidant defense in juvenile Oreochromis niloticus

Aquaculture farming often faces diseases, causing economic loss. Probiotics offers an eco-friendly alternatives antibiotic, improving fish health, immunity, and resistance, without adverse side effects. This study evaluated the probiotic potential of two enzyme producing probiotic strains, DAS-SCF02 and RKDAS1, isolated from the gut of Channa striata . Molecular identification using 16S rRNA gene sequencing confirmed their taxonomy and phylogenetic relationships. Juvenile Oreochromis niloticus were fed diets supplemented with 1×10 8 CFU/g of these isolates, either individually or in combination, for 60 days. Growth performance parameters including final average body weight (FABW), weight gain (WG), specific growth rate (SGR), and feed conversion ratio (FCR) were significantly improved ( P < 0.05) in probiotic-treated groups, with the dual-strain diet (Diet 4) showing the most pronounced effects. Digestive enzyme activities (amylase, protease, and cellulase) were also markedly elevated in treated fish. Furthermore, antioxidant biomarkers such as total antioxidant capacity (T-AOC), superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) were significantly increased, while malondialdehyde (MDA) levels were reduced, indicating enhanced oxidative stress resistance. These findings suggest that DAS-SCF02 and RKDAS1 are promising probiotic candidates for improving growth performance, digestive efficiency, and antioxidant defense in O. niloticus , supporting their application in sustainable aquaculture.