Saccharomyces Cerevisiae Modification For Ethanol And Electricity Co-production In Microbial Fuel Cells

In microbial fuel cells,an increase in intracellular electrons contributes to the performance of microbial fuel cells.In this study,by knocking out genes related to the intracellular pyruvate metabolism and electron consumption in the TCA cycle in Saccharomyces cerevisiae,excess electrons were accumulated intracellularly.The elevated intracellular electron pool had a positive impact on the electricity production performance of the microbial fuel cell,and also helped to increase ethanol production and achieve ethanol and electricity co-production,which in turn improved the energy utilization of the substrate.The knockdown of lactate dehydrogenase in strainΔdld123 resulted in a maximum ethanol yield of 7.71 g/L,a conversion rate of 0.386 g/g,an open circuit voltage of 0.65 V,an increase of 16%compared to the original strain,and an external circuit voltage of 0.411 V,an increase of 157%.The maximum power density in the MFC reached 240 mW/m~2,a 12-fold increase in power density.The total energy utilization has increased by 17.3%.Among the strains knocking out the genes related to electron consumption in the TCA cycle,all the knockout strains showed a decrease in ethanol yield compared to the original 5D strain,except for theΔmdh1 knockout strain which reached a maximum ethanol yield of 7.33g/L.The maximum open circuit voltage ofΔoye3 andΔidp1 reached 0.631 V and 0.615 V,respectively,which increased by 12.7%and 9.8%compared with the original bacteria.TheΔidp2 andΔoye3 knockout strains had external circuits of 0.274 V and 0.409 V,respectively,and theΔoye3 strain reached a maximum power density of 103.6 mW/m~2 with improved electricity production performance.The NADH/NAD~+ratio of theΔdld123 knockout strain was 2.8times higher than that of the original 5D bacterium,and the intracellular NADPH/NADP~+values of theΔoye3 knockout strain andΔidp2 knockout strain were 1.87 and 1.85 times higher than those of the original 5D bacterium,respectively,demonstrating the accumulation of intracellular electrons.In addition,this paper also did the introduction of the xylose metabolic pathway into the yeast cytosol,enabling Saccharomyces cerevisiae to use other carbon sources for ethanol electricity co-production.Ethanol production reached a maximum of 8.2 g/L with a maximum power density of 72.4 mW/m~2for theΔdld123-xly strain.Intracellular expression of membrane proteins in yeast to improve electron transfer efficiency showed that the growth of the membrane protein modified strain was inhibited and ethanol production was around 5-6 g/L.Compared to the original bacteria,ethanol production and power generation performance were reduced.