Metabolic activity and pathway study of aspirin biodegradation using a microbial electrochemical system supplied by an alternating current.

The main aim of this study is to investigate the biodegradation of highly concentrated aspirin as an emerging pollutant from aqueous solution using an alternating current microbial electrochemical system. A single-chamber Plexiglas cylindrical reactor equipped with stainless steel mesh electrodes (18 cm height × 16 cm diameter) was applied as the bioreactor in batch mode with an effective volume of 5 L, height of 20 cm, and the diameter about 20 cm by AMPL = 2 V, OFST = 0.1 V, waveform = sinusoidal, frequency = 10 Hz, and pH = 7. The process parameters including initial concentration (100-400 mg L), chemical oxygen demand (COD), activity of enzymes, biokinetic and pathway studies at very low voltage and very low frequency alternating current were investigated. The specific biodegradation rate of aspirin was calculated based on Michaelis-Menten model. The complete aspirin removal efficiency and the maximum enzymatic activity were achieved at 250 mg L aspirin, voltage of 2 V and applied current = 3 mA during 6 h. The bioassay of aspirin concentrations in biofilm of the system using flow cytometry analysis resulted in the live and necrotic cells shares of 96.2%, and 0.44%, respectively. Moreover, the LC and GC-MS analysis showed low molecular weight acids such as oxalic and acetic acid at 6 h time under the optimal conditions using very low applied voltage and frequency. Obtaining low reaction time for degradation, high potential in biodegradation, oxidation and mineralization ability were the novelty of treatment system with high concentration aspirin in the study.