Simultaneous Production Of Biohydrogen And Bioelectricity From Xylose With Microbial Fuel Cell:Performance And Mechanism

A wide range using of fossil fuels has caused major environmental challenges.Therefore,environmental-friendly renewable energy resources such as solar energy,wind energy,and biomass energy have been considered to facilitate sustainable energy development and environmental challenges.Among them,biomass energy has been regarded to be one of the renewable energy resources with high capability.Thus,microbial fuel cell?MFC?is a new technology that can directly and efficiently convert organic compounds into electrical energy,which holds extensive applications.Although now,MFC efficiency from biomass conversion is low,in which one of the main limiting factors is faced with the difficulty of MFC for efficiently converting biomass-derived xylose into energy products.According to this key limiting factor,strain screening method was assayed to isolate a new type of exoelectrogenic strain that can generate electricity using xylose as a sole carbon source with efficient utilization of xylose in MFC.Further,it was found that the MFC can produce hydrogen while xylose is used to generate electricity,and it can enable simultaneous conversion of xylose into biohydrogen and bioelectricity production,which provides a new pathway and potential for the efficient energy harvesting from xylose.The main research contents and results are as follows;Strain screening method was aimed to achieve a new type of exoelectrogenic microorganism for xylose-fueled MFC.In order,we isolated and identified a new exoelectrogenic yeast strain?Cystobasidium slooffiae strain JSUX1?that can generate bioelectricity using xylose as a sole carbon and energy source in MFC.After adaptation,it produced significant current density with rapid xylose metabolism.More surprisingly,the isolated strain produced biohydrogen either in anaerobic flask incubation or in MFC,which delivered 67 mW/m² power output and 23 L/m³biohydrogen in MFC.Further,the electrochemical analysis indicated that riboflavin was secreted by strain JSUX1 as an electron mediator for efficient electron transfer between cells and electrode in MFC.Next,electrode modification methods were developed to improve the performance of xylose-fueled MFC.We used polyaniline?PANI?polymers to modify carbon felt?CF?,and carbon cloth?CC?electrodes surface.The PANI-modified electrode was characterized by SEM,FTIR,Raman,and XRD analysis.Raman shift peaks showed the most intense peaks in the stretching region of 1487 cm^-1 assigned to C=N as a function of charge potential,and the located band on 1586 cm^-1 corresponds to C=C quinoid ring as an oxidizing agent.Further,FTIR analysis detected the bands at 1558 cm^-1,1521 cm^-1,1488 cm^-1 that were corresponded to C-C chain,and 1295 cm^-1,1241 cm^-1,1123 cm^-1 were referred to C-O ring stretching.Besides,XRD pattern showed the highest degree of crystallinity in the domain of 25 and 20 angle degrees,which were compatible with amine and phenolic groups presented in the structural ring.The effect of PANI modification on MFC performance revealed an enhancement on bioelectricity about119 mW/m² and biohydrogen production about 37.3 L/m³.Further,biofilm analysis indicated that PANI modification can highly enhance the cell loading on the electrode surface,which resulted in MFC performance.Moreover,we used graphene oxide?GO?for electrodes surface modification to further improve the MFC performance.Interestingly,GO was biologically reduced to rGO by yeast cell strain JSUX1 and formed a 3D-rGO hydrogel on the surface of the electrodes.The characterization of GO and rGO with XRD pattern showed a peak with pure GO at the reflection plane of?001?,while the biologically produced rGO showed peaks at reflection planes of?002?and?110?.Further,the reduction of GO to rGO by yeast strain was confirmed by FTIR and Raman analysis.The effect of GO modification on MFC performance revealed an enhancement on bioelectricity about 150 mW/m² and biohydrogen production about 48 L/m³.Moreover,the electrochemical analysis indicated that EET of MET for riboflavin was enhanced and the charge transfer resistance between cells and electrodes was largely decreased,which was the underlying mechanism for performance improvement by GO modification.In summary,this work isolated a new exoelectrogenic eukaryotic microorganism that can simultaneously produce biohydrogen and bioelectricity from xylose,and it could develop an efficient xylose-fueled MFC for biohydrogen and bioelectricity production,which would diversify the toolbox of biomass energy.