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The Microbial Fuel Cell (MFC) is a bio-electrochemical transducer converting waste products into electricity using microbial communities. Cellular Automaton (CA) is a uniform array of nite-state machines that update their states in discrete time depending on states of their closest neighbors by the same rule. Arrays of MFCs could, in principle, act as massive-parallel computing devices with local connectivity between elementary processors. We provide a theoretical design of such a parallel processor by implementing CA in MFCs. We have chosen Conway's Game of Life as the `benchmark' CA because this is the most popular CA which also exhibits an enormously rich spectrum of patterns. Each cell of the Game of Life CA is realized using two MFCs. The MFCs are linked electrically and hydraulically. The model is veri ed via simulation of an electrical circuit demonstrating equivalent behaviors. The design is a rst step towards future implementations of fully autonomous biological computing devices with massive parallelism. The energy independence of such devices counteracts their somewhat slow transitions | compared to silicon circuitry | between the di erent states during computation. ; This work was supported by the European Union's Horizon 2020 Research and Innovation Programme under Grant Agreement No. 686585.

A cellular non-linear network (CNN) is a uniform regular array of locally connected continuous-state machines, or nodes, which update their states simultaneously in discrete time. A microbial fuel cell (MFC) is an electro-chemical reactor using the metabolism of bacteria to drive an electrical current. In a CNN model of the MFC, each node takes a vector of states which represent geometrical characteristics of the cell, like the electrodes or impermeable borders, and quantify measurable properties like bacterial population, charges produced and hydrogen ions concentrations. The model allows the study of integral reaction of the MFC, including temporal outputs, to spatial disturbances of the bacterial population and supply of nutrients. The model can also be used to evaluate inhomogeneous con gurations of bacterial populations attached on the electrode bio lms. ; This work was funded by the European Union's Horizon 2020 Research and Innovation Programme under Grant Agreement No. 686585. https://ec.europa.eu/programmes/horizon2020/

Microbial fuel cells, in which microorganisms catalyze the transfer of electrons released from the oxidation of organic compounds onto an electrode, are a promising biotechnological approach for harvesting energy in the form of electricity from certain wastes. The purpose of this study was to determine if landfill leachate is a productive source of substrate and microbes for generating electricity in microbial fuel cells. Research methods included filling the anodic chambers of multiple fuel cells with landfill leachate. The cathodic chambers were filled with a buffer solution of KH2PO4 and were separated from the anodic chambers by a proton exchange membrane (NafionTM). Graphite plates were used as the electrodes in both chambers. Findings from this study show that microorganisms in landfill leachate are electrochemically active, and thus, landfill leachate can be an effective source of bio-electricity. Further results indicate that these electricity-producing microbes reside on the graphite anode, as opposed to being suspended throughout the leachate fluid. Experiments indicated that the leachate may lack enough carbon constituents (or food sources) to support long-term electrical generation. The addition of 10 mL of a 0.4% soluble sugar mixture (0.1% each of glucose, cellobiose, maltose, and xylose) provided enough food source for the microorganisms in the leachate to generate electrical voltage that was nearly three times the amount produced without the sugar mixture (0.120 volts). Furthermore, this maximum voltage generation (0.450 volts) continued for nearly two weeks, over twice the length of generation for the leachate without sugar. Additionally, leachate Chemical Oxygen Demand (COD) levels were reduced in initial tests after fuel cell electrical generation was complete, indicating that microbial fuel cells are potentially effective in treating landfill leachate. A cost analysis of a conceptual large scale design indicated that MFC technology is not mature enough to justify the implementation of this design based on economics alone. However, as energy costs continue to rise and MFC power production is maximized, MFC implementation could become more feasible. ; Ohio State University. College of Engineering ; Ohio State University. Dept. of Food, Agricultural, and Biological Engineering ; Ohio State University. Chapter of Sigma XI ; Ohio State University. Undergraduate Student Government

[Background] Microbial fuel cells (MFCs) operating with complex microbial communities have been extensively reported in the past, and are commonly used in applications such as wastewater treatment, bioremediation or in-situ powering of environmental sensors. However, our knowledge on how the composition of the microbial community and the different types of electron transfer to the anode affect the performance of these bioelectrochemical systems is far from complete. To fill this gap of knowledge, we designed a set of three MFCs with different constrains limiting direct and mediated electron transfer to the anode. ; [Results] The results obtained indicate that MFCs with a naked anode on which a biofilm was allowed unrestricted development (MFC-A) had the most diverse archaeal and bacterial community, and offered the best performance. In this MFC both, direct and mediated electron transfer, occurred simultaneously, but direct electron transfer was the predominant mechanism. Microbial fuel cells in which the anode was enclosed in a dialysis membrane and biofilm was not allowed to develop (MFC-D), had a much lower power output (about 60% lower), and a prevalence of dissolved redox species that acted as putative electron shuttles. In the anolyte of this MFC, Arcobacter and Methanosaeta were the prevalent bacteria and archaea respectively. In the third MFC, in which the anode had been covered by a cation selective nafion membrane (MFC-N), power output decreased a further 5% (95% less than MFC-A). In this MFC, conventional organic electron shuttles could not operate and the low power output obtained was presumably attributed to fermentation end-products produced by some of the organisms present in the anolyte, probably Pseudomonas or Methanosaeta. ; [Conclusion] Electron transfer mechanisms have an impact on the development of different microbial communities and in turn on MFC performance. Although a stable current was achieved in all cases, direct electron transfer MFC showed the best performance concluding that biofilms are the major contributors to current production in MFCs. Characterization of the complex microbial assemblages in these systems may help us to unveil new electrogenic microorganisms and improve our understanding on their role to the functioning of MFCs. ; This work was partially funded by projects RTC-2016-5766-2, CTQ2014–54553-C3–2-R and CTQ2014–61809-EXP to JM from the Spanish Government, with participation of the European Regional Development Fund. ; Peer reviewed

[Background] Microbial fuel cells (MFCs) operating with complex microbial communities have been extensively reported in the past, and are commonly used in applications such as wastewater treatment, bioremediation or in-situ powering of environmental sensors. However, our knowledge on how the composition of the microbial community and the different types of electron transfer to the anode affect the performance of these bioelectrochemical systems is far from complete. To fill this gap of knowledge, we designed a set of three MFCs with different constrains limiting direct and mediated electron transfer to the anode. ; [Results] The results obtained indicate that MFCs with a naked anode on which a biofilm was allowed unrestricted development (MFC-A) had the most diverse archaeal and bacterial community, and offered the best performance. In this MFC both, direct and mediated electron transfer, occurred simultaneously, but direct electron transfer was the predominant mechanism. Microbial fuel cells in which the anode was enclosed in a dialysis membrane and biofilm was not allowed to develop (MFC-D), had a much lower power output (about 60% lower), and a prevalence of dissolved redox species that acted as putative electron shuttles. In the anolyte of this MFC, Arcobacter and Methanosaeta were the prevalent bacteria and archaea respectively. In the third MFC, in which the anode had been covered by a cation selective nafion membrane (MFC-N), power output decreased a further 5% (95% less than MFC-A). In this MFC, conventional organic electron shuttles could not operate and the low power output obtained was presumably attributed to fermentation end-products produced by some of the organisms present in the anolyte, probably Pseudomonas or Methanosaeta. ; [Conclusion] Electron transfer mechanisms have an impact on the development of different microbial communities and in turn on MFC performance. Although a stable current was achieved in all cases, direct electron transfer MFC showed the best performance concluding that biofilms are the major contributors to current production in MFCs. Characterization of the complex microbial assemblages in these systems may help us to unveil new electrogenic microorganisms and improve our understanding on their role to the functioning of MFCs. ; This work was partially funded by projects RTC-2016-5766-2, CTQ2014–54553-C3–2-R and CTQ2014–61809-EXP to JM from the Spanish Government, with participation of the European Regional Development Fund. ; Peer reviewed