Abstract
Soil has been used to generate electrical power in microbial fuel cells (MFCs) and exhibited several potential applications. This study aimed to reveal the effect of soil properties on the generated electricity and the diversity of soil source exoelectrogenic bacteria. Seven soil samples were collected across China and packed into air-cathode MFCs to generate electricity over a 270 days period. The Fe(III)-reducing bacteria in soil were enriched and sequenced by Illumina pyrosequencing. Culturable strains of Fe(III)-reducing bacteria were isolated and identified phylogenetically. Their exoelectrogenic ability was evaluated by polarization measurement. The results showed that soils with higher organic carbon (OC) content but lower soil pH generated higher peak voltage and charge. The sequencing of Fe(III)-reducing bacteria showed that Clostridia were dominant in all soil samples. At the family level, Clostridiales Family XI incertae sedis were dominant in soils with lower OC content but higher pH (>8), while Clostridiaceae, Lachnospiraceae, and Planococcaceae were dominant in soils with higher OC content but lower pH. The isolated culturable strains were allied phylogenetically to 15 different species, of which 11 were Clostridium. The others were Robinsoniella peoriensis, Hydrogenoanaerobacterium saccharovorans, Eubacterium contortum, and Oscillibacter ruminantium. The maximum power density generated by the isolates in the MFCs ranged from 16.4 to 28.6 mW m-2. We concluded that soil OC content had the most important effect on power generation and that the Clostridiaceae were the dominant exoelectrogenic bacterial group in soil. This study might lead to the discovery of more soil source exoelectrogenic bacteria species.
Highlights
Soil can be used to generate electrical power in microbial fuel cells (MFCs), which convert chemical energy from soil organic compounds into electricity via catalysis by soil source exoelectrogenic microorganisms
Soil samples were collected from seven sites, which were located in the Inner Mongolia Autonomous Region (IM), Hebei Province (HB), Henan Province (HN), Jiangsu Province (JS), Jiangxi Province (JX), Fujian Province (FJ), and Guangxi Zhuang Autonomous Region (GX), respectively
We investigated the characters of power generation by seven soils in MFCs over a 270 days period, and revealed that the soil organic carbon (OC) content had the most important effect on power generation
Summary
Soil can be used to generate electrical power in microbial fuel cells (MFCs), which convert chemical energy from soil organic compounds into electricity via catalysis by soil source exoelectrogenic microorganisms. The pollutant toxicity and soil microbial activity could be monitored by the generated electrical signals of the MFCs, such as peak voltage, quantity of electrons and start-up time MFCs do not need energy input, instead, a small amount of electrical power is generated. The performance of these MFCs is largely related to the magnitude of electrical current generated by the exoelectrogenic bacteria in soil. Little is known about the character of power generation and the diversity of exoelectrogenic bacteria in different soils
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