Study On The Treatment Of Biodiesel Byproduct Crude Glycerol By Microbial Fuel Cell Method

Microbial fuel cells?MFCs?,as a new type of fuel cell,have been widely used in renewable energy applications,energy production and waste disposal,owing to its diverse fuel sources and green process characteristics,which could directly convert organic fuels into electrical energy for recycling.In recent years,biodiesel as a renewable biomass energy,that has the potential to replace fossil fuels,has been widely used and promoted by various governments.However,a large amount of crude glycerol has been accumulated in the refining process,bringing about the market and the environment huge stress.Therefore,there is an urgent need to seek a green and environmentally friendly technical method to rationally and effectively recycle or use crude glycerol and convert them into value-added products.In this study,a consortium two-chamber MFC was constructed.Glycerol was used as the sole carbon source,Klebsiella peneumoniae and Shewanella oneidensis were used as anodic strains and K₃[Fe?CN?₆]solution was used as catholyte.We studied the effect of different strains,mixing ratios,carbon metabolism flow distribution,and EET on electrical performance of MFCs through electrochemical and synthetic biology and other research methods.We also systematically analyzed the advantages and features of simultaneous consuming glycerol and recovering electric energy by MFCs.The main achievements of the above research include:?1?Broaden the carbon source utilization spectrum of MFCs.Pure S.oneidensis MFCs is hardly to use glycerol as carbon source to produce electricity.However,as K.peneumoniae was added as fermentative strain,the power production of MFCs could be significantly improved,with a maximum output voltage?127 mV?and power density?8.17 mW/m²?.Such a result indicated that rational combination of different strains can broaden the carbon source utilization spectrum of MFCs.?2?The output voltage produced by MFCs is different,when K.peneumoniae and S.oneidensis are mixed at different inoculation ratios.This study compared the output voltages of MFCs with 1:5,1:10 and 1:15 inoculation ratios.The results showed that K.peneumoniae and S.oneidensis,when mixed at the value of OD₆₀₀ was 0.05 and 0.5spectively,had the best electrical performance are in better real estate performance.Its maximum output voltage was up to 114 mV,while the other two value are respectively 99 mV and 108 mV.?3?Rationally regulate the intracellular carbon metabolic flux distribution of K.peneumoniae and EET efficiency between S.oneidensis and electrodes can significantly increase MFCs'ability to produce electricity and utilize glycerol.Synthetic biology technology was used to knock out the ethanol metabolism pathway of K.peneumoniae,and a heterologous expression pathway of lactic acid was introduced to make more carbon source flow towards the favorable direction of MFCs'production of electricity.At the meantime,a heterologous expression pathway of riboflavin was introduced into S.oneidensis,which acted as the electron transport,to accelerate the extracellular electron transfer?EET?between S.oneidensis and the electrodes.The results showed that more than 98%of the ethanol was reduced,lactic acid production increased by 350%,and riboflavin production increased by 790%.Finally,the maximum output voltage of MFCs reached 233 mV,and the power density increased from 8.17 mW/m² to 19.9 mW/m².?4?The consumption speed of glycerol was accelerated.We compared different types MFCs,such as single strains,mixed strains,wild type strains,and engineered strains.The results showed that the consumption speed of consortium MFCs was superior to that of single strains of MFCs.At the same time,the engineered MFCs performed better than wild-type.The results showed that the EET of exoelectrogen can accelerate the glycerol consumption speed of the fermenter.