Bacillus subtilis probiotic enhances ornamental fish survival through ammonia detoxification

Abstract

Ammonia nitrogen (NH₃-N) pollution poses a critical challenge to global aquaculture sustainability. Here, we report the isolation and characterization of Bacillus subtilis DM115, a novel probiotic strain that demonstrates exceptional NH₃-N degradation capabilities in ornamental fish aquaculture. Under optimized conditions, DM115 achieved 98.45% NH₃-N reduction within 24 h, while exhibiting broad-spectrum antimicrobial activity against major aquaculture pathogens with minimal antibiotic resistance. In vivo studies using koi (Cyprinus rubrofuscus haematopterus) revealed that DM115 not only effectively reduced NH₃-N levels to 0.25 mg/L (99.37% efficiency) but also significantly enhanced fish survival (86.67%) through modulation of antioxidant enzyme activities and inflammatory response pathways. Our findings establish DM115 as a promising probiotic agent for sustainable aquaculture water quality management, offering an environmentally conscious alternative to conventional treatment methods.