| Corn cobs,as a cellulosic waste biomass,is a crop by-product with abundant production in China,but it can cause serious damage to our water,air,and soil environment if it is not properly disposed of.Microbial electrochemical system(MES)is a technology that can convert the chemical energy contained in biomass into electrical energy,and it can generate electrical energy from biomass,which can realize the resource utilization of corn cobs.However,cellulose-based biomass is difficult to be directly utilized by electricity-producing bacteria in the MES anode chamber,and long-term operation will affect the electricity-producing performance of the reactor.Therefore,in this paper,corn cobs were hydrothermally pretreated,enzymatically treated,and hydrolyzed and acidified to obtain three hydrolysates,and the electrochemical performance of each system was investigated using each hydrolysate as MES anode solution,and the microbial community structure of the anode biofilm of each MES was analyzed in the following process:In this paper,corn cobs were firstly crushed to obtain corn cob powder,and the enzymatic solution was obtained by hydrothermal pretreatment of corn cob powder and then cellulase was added to the enzymatic solution,after which the anaerobic hydrolytic acidification of the enzymatic solution was carried out using granular sludge to obtain the acidification solution rich in volatile acids,and the concentration of each component during the reaction was observed regularly.The optimal time for the enzymatic reaction was determined to be 12 h and the optimal time for the hydrolytic acidification reaction was determined to be 16 h,which saved the reaction time and reduced the nutrient loss to provide the hydrolysate required for subsequent experiments.Four groups of MES reactors were started and named C1,C2,C3 and C4,respectively,and electrochemical tests were conducted after incubation with sodium acetate carbon source until maturity,and the C1,C2 and C3 reactors with closer performance were selected according to the test results,and the maximum power densities measured after the addition of acidification solution,enzymatic solution and hydrothermal treatment solution were 912.6 m W/m2,821.4 m W/m2,814.5 m W/m2,814.5 m W/m2,814.5 m W/m2 and 814.5 m W/m2,respectively,814.5 m W/m2,and the COD degradation rates of the anode solution at the end of the single cycle were89.3%,86%,and 82%,respectively,in addition to the high decomposition rates of reducing sugars and volatile acids in the anode solution.The decomposition utilization rates of acetic acid,propionic acid,n-butyric acid,isobutyric acid,n-valeric acid,and isovaleric acid in the anode solution at the end of the cycle for C1 with the best electrochemical performance were 90.5%,95.9%,75%,87.7%,73.2%,and 81.7%,respectively.The highest values of COD removal were 89.2%,85.8%,and 81.2% for C1,C2,and C3,respectively,and the highest values of coulometric efficiency were 26.69%,19.84%,and 15.73% for different COD concentration gradients in the anode solution.C1,C2 and C3 were analyzed for the microbial community structure of the anode biofilm at the end of the experiment,and the main phylum of electricity-producing bacteria observed in each reactor were Proteobacteria and Firmicutes,and the percentage of abundance occupied by Clostridia phylum in C2 and C3 were 12% and 14.8%,respectively,and the percentage occupied by Bacilli phylum in C2 was as high as Geobacter,Dysgonomonas,Desulfovibrio were the main genera of electricity producing bacteria in each MES,and Dysgonomonas and Pleomorphomonas were observed in C3 because the main component of the anodic solution was xylose,which occupied a higher proportion.This experiment proved that the acidified solution is more suitable as the anodic substrate substrate for MES. |
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