Synergistic bio-electrocatalysis by a defined Enterobacter sp. - Methanoculleus sp. co-culture enables antibiotic mixture degradation and methane recovery

Antibiotic contamination in wastewater poses dual threats: environmental toxicity and the proliferation of antimicrobial resistance, while rising demand for renewable energy calls for integrated remediation strategies. Here, we employed a defined bio-electrochemical system (BES) coupling a multi-antibiotic degrading bacterium (Enterobacter sp. ACD-08) with a hydrogenotrophic methanogen (Methanoculleus sp. MB-04) to achieve simultaneous degradation of a six-antibiotic mixture and methane (CH₄) production. Under optimized conditions (120 mg/L antibiotic mixture (20 mg/L each), pH 6.8, 37 °C, applied potential 0.8 V), the system achieved >79% removal for all antibiotics. Cumulative CH₄ production reached 7.55 ± 0.78 mmol, and total chemical oxygen demand (COD) removal exceeded 91.3 ± 1.02%, demonstrating effective conversion of antibiotic-derived intermediates into bioenergy. Mechanistic analyses revealed that ACD-08 oxidized antibiotics to volatile fatty acids at the bio-anode, which were subsequently utilized by MB-04 at the bio-cathode for CH₄ generation. BES stimulation further enhanced extracellular electron transfer, microbial growth, and enzymatic activities, resulting in reduced oxidative stress and increased biomass. Comparative treatments confirmed that neither the degrader nor the methanogen alone achieved concurrent pollutant removal and bioenergy recovery, highlighting the synergistic interplay enabled by BES. This study establishes a robust, reproducible platform for integrated antibiotic remediation and renewable energy recovery, offering a sustainable strategy for pharmaceutical wastewater treatment.