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Open Access Research

Microbial community structures differentiated in a single-chamber air-cathode microbial fuel cell fueled with rice straw hydrolysate

Zejie Wang14, Taekwon Lee35, Bongsu Lim1, Chansoo Choi2* and Joonhong Park3

Author Affiliations

1 Department of Environmental Engineering, Daejeon University, Daejeon, South Korea

2 Department of Applied Chemistry, Daejeon University, Daejeon, South Korea

3 School of Civil and Environmental Engineering, Yonsei University, Seoul, South Korea

4 Institute of Urban Environment, Chinese Academy of Sciences, Urban, China

5 Department of Microbiology and Ecosystem Science, University of Vienna, Vienna, Austria

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Biotechnology for Biofuels 2014, 7:9  doi:10.1186/1754-6834-7-9

Published: 17 January 2014

Abstract

Background

The microbial fuel cell represents a novel technology to simultaneously generate electric power and treat wastewater. Both pure organic matter and real wastewater can be used as fuel to generate electric power and the substrate type can influence the microbial community structure. In the present study, rice straw, an important feedstock source in the world, was used as fuel after pretreatment with diluted acid method for a microbial fuel cell to obtain electric power. Moreover, the microbial community structures of anodic and cathodic biofilm and planktonic culturewere analyzed and compared to reveal the effect of niche on microbial community structure.

Results

The microbial fuel cell produced a maximum power density of 137.6 ± 15.5 mW/m2 at a COD concentration of 400 mg/L, which was further increased to 293.33 ± 7.89 mW/m2 through adjusting the electrolyte conductivity from 5.6 mS/cm to 17 mS/cm. Microbial community analysis showed reduction of the microbial diversities of the anodic biofilm and planktonic culture, whereas diversity of the cathodic biofilm was increased. Planktonic microbial communities were clustered closer to the anodic microbial communities compared to the cathodic biofilm. The differentiation in microbial community structure of the samples was caused by minor portion of the genus. The three samples shared the same predominant phylum of Proteobacteria. The abundance of exoelectrogenic genus was increased with Desulfobulbus as the shared most abundant genus; while the most abundant exoelectrogenic genus of Clostridium in the inoculum was reduced. Sulfate reducing bacteria accounted for large relative abundance in all the samples, whereas the relative abundance varied in different samples.

Conclusion

The results demonstrated that rice straw hydrolysate can be used as fuel for microbial fuel cells; microbial community structure differentiated depending on niches after microbial fuel cell operation; exoelectrogens were enriched; sulfate from rice straw hydrolysate might be responsible for the large relative abundance of sulfate reducing bacteria.

Keywords:
Microbial fuel cell; Microbial diversity; 454-pyrosequencing; Rice straw biomass