Doxycycline degradation by Enterobacter cloacae HS-08: A comparative analysis of biodegradation and bio-electrodegradation approaches with toxicity implications

Doxycycline (DOX), a commonly prescribed antibiotic, poses a growing environmental concern due to its recalcitrant nature, insufficient removal by conventional treatment methods, and detrimental effects on ecosystems and living organisms. This study evaluates the comparative efficacy of biodegradation and bio-electrodegradation approaches for DOX removal using Enterobacter cloacae HS-08, focusing on degradation efficiency, intermediate toxicity, systemic impacts, and gut microbiome alterations. The results showed that biodegradation achieved 61% DOX removal (75 mg/L) within 8 days; however, HPLC-MS/MS analysis revealed the formation of toxic intermediates, resulting in residual toxicity. Interestingly, bio-electrodegradation demonstrated superior performance, achieving 99.19% degradation under optimized conditions with minimal toxic intermediates. In-vivo toxicity studies using mice revealed that untreated DOX effluent significantly reduced body weight, food intake, and organ health while disrupting gut microbiome composition, marked by reduced diversity and dysbiosis. Biodegradation effluent exhibited moderate toxicity, reflecting the lingering effects of intermediate by-products. Conversely, bio-electrodegradation effluent mitigated toxicity, preserved gut microbiome structure and diversity, and supported normal physiological function, with growth, appetite, and organ health comparable to the control group. These findings highlight the critical need to address doxycycline contamination and emphasize the superior efficacy of bio-electrodegradation as a sustainable solution for mitigating pharmaceutical pollutants and restoring ecological balance.