Increasing the temperature is a relevant strategy to form microbial anodes intended to work at room temperature

Abstract

OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. Reducing the time required for the formation of microbial anodes from environmental inocula is a great challenge. The possibility of reaching this objective by increasing the temperature during the bioanode preparation was investigated here. Microbial anodes were formed at 25 C and 40 C under controlled potential with successive acetate additions. At 25 C, around 40 days were required to perform three acetate batches, which led to current density of 9.4 ± 2 A.m À2 , while at 40 C, 20 days were sufficient to complete three similar batches, leading to 22.9 ± 4.2 A.m À2 . The bioanodes formed at 40 C revealed three redox systems and those formed at 25 C only one. The temperature also impacted the biofilm structure, which was less compact at 40 C. When the bioanodes formed at 40 C were switched to 25 C, they produced current densities similar to those of bioanodes formed at 25 C; they recovered the single redox system that was developed by the bioanodes formed at 25 C and the difference in biofilm structures was mitigated. It is consequently fully appropriate to accelerate the formation of microbial anodes by increasing the temperatures to 40 C even if they are finally intended to operate at room temperature.

Factors affecting the efficiency of a bioelectrochemical system: a review

“…Microbial anodes perform a core function in a BES: they oxidize various resistant organic compounds, including polycyclic aromatic hydrocarbons (PAHs), phenols, and polychlorinated biphenyls (PCBs), that cannot be degraded easily under natural conditions. 7,11,28,29 The system is constructed either for electricity generation via spontaneous redox reactions (in MFCs) or applying external electrical power to initiate an otherwise nonspontaneous reaction to produce value-added products, such as hydrogen reduced from protons (in MECs) or methane reduced from carbon dioxide (via microbial electrosynthesis). [1][2][3]25 Theoretically, the potential of the redox reaction occurring on the surface of the electrodes determines the potential of the electrodes and the spontaneity of the reaction.…”

“…32,61 For most microorganisms, 35-40 C is the optimum temperature range for growth, enzyme activity, and formation of a stable biolm, thereby increasing the substrate degradation rate and the electricity production in the BES. 29,32,62,63 In many studies, increasing the temperature will increase the power output of the BES. It was demonstrated that the Arrhenius law is followed between anode current output and temperature in the range of 30-45 C. 63 However, when the temperature reaches a certain level, the activity and structure of the microbial enzyme are impaired, thereby reducing the performance of the BES.…”

“…69 Consequently, it may be desirable to heat the wastewater (e.g., to 40 C) during the establishment of the anode biolm. 29 Considering the adverse effects of high temperatures on the system's energy production, we could start the system at a high temperature and then operate at a relatively low temperature. In addition to the direct inuence of temperature on microorganisms in the BES, there are also effects on the physical and chemical properties of the treatment media (water, sediment, soil, etc.…”

Solar Photothermal Electrodes for Highly Efficient Microbial Energy Harvesting at Low Ambient Temperatures

“…[3] However, the successful commercializationo fM FCs has been strongly hindered because of their low powero utputs. [5] In general, op-timal temperatures enablef ast start-upa nd better anode performance of the MFCs because the anodic biofilm formation is faster and enzymesa re more active. [4] Te mperature fluctuation is one of the keyi ssues that must be solved to achieveh igh-performance MFCs.…”

“…[4] Te mperature fluctuation is one of the keyi ssues that must be solved to achieveh igh-performance MFCs. [5] In general, op-timal temperatures enablef ast start-upa nd better anode performance of the MFCs because the anodic biofilm formation is faster and enzymesa re more active. [6] Low ambientt emperatures lead to al ower microbial bioelectrocatalytic activity and metabolic rates, which impacts the rate of electric energy conversion of MFCs.…”