Study On The Enhanced Performance Of Metal Dependent Anaerobic Oxidation Of Methane By Electronic Shuttle

The methane in the atmosphere contributes 20%to the current global warming,and is increasing at a rate of 0.5%to 1%year by year.Metal-dependent methane anaerobic oxidation can effectively reduce greenhouse gas methane emissions.However,the complicated material transport and electron transport mechanisms have led to the disadvantages of long growth cycle,slow metabolic rate,and low methane anaerobic oxidation rate.The electronic shuttle can participate in the redox reaction cyclically,increase the extracellular electron transfer rate,and strengthen the effect of anaerobic biological treatment of pollutants.Therefore,this study aims to promote the extracellular electron flux of methane anaerobic oxidizing bacteria through the electronic shuttle to strengthen the performance of metal-dependent methane anaerobic oxidation.The paper takes the metal-dependent methane anaerobic oxidizing bacteria as the research object,and studies the enhancement effect on the anaerobic oxidation of methane and the electron transfer activity of microorganism by adding 4 kinds of exogenous electron shuttle formed from L-cysteine,AQC,2-HNQ and neutral red.The results showed that the rate of methane deceleration in the L-cysteine and neutral red groups was1.3 times and 2.6 times that the control group,while AQC and 2-HNQ reduced the rate of methane deceleration;all four electronic shuttles slowed down Mn.(II)formation rate,and the process of AOM coupling?-Mn O₂ reduction to Mn(II)follows zero-order reaction kinetics(R²>0.91).The results of TTC-ETS activity and INT-ETS activity both showed that neutral red and L-cysteine can significantly improve the electron transport activity of microorganisms,but the correlation between TTC-ETS activity and methane deceleration rate is higher.The paper reveals the effect of the external electronic shuttle on the electron transfer efficiency of the Metal-AOM.L-cysteine and neutral red increase the hydrophilicity of microbial aggregates,which is beneficial to the microorganisms to improve the material transport ability,while AQC increases the hydrophobicity of microbial aggregates.The correlation analysis found that the methane reduction reaction rate ratio(K_ES/K₀)had a linear negative correlation with the electron shuttle redox potential E⁰(R²=0.9717).The methane deceleration rate did not increase with the increase of the electronic shuttle ETC,and too low EDC to increase the reaction kinetic rate,and the reasonable EAC/ETC proportion can effectively increase the methane deceleration rate.Through electrochemical means,it was found that L-cysteine can effectively increase the electron flux of microbial extracellular respiration.The biofilm showed a significant reduction peak,and the oxidation peak was extremely weak.The L-cysteine group biofilm electron transfer rate kapp was 1.18 times that the control group,and the biofilm extracellular electron transfer rate was accelerated.In summary,L-cysteine and neutral red have relatively low redox potentials and a reasonable EAC/ETC proportion,which improves the ability of microbial aggregates to obtain substances and metabolic activity,enhances the extracellular transfer electron circulation,and strengthens The metal-dependent methane anaerobic oxidation performance.