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

Abstract

BackgroundThe 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.ResultsThe 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.ConclusionThe 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.

Different methods used to form oxygen reducing biocathodes lead to different biomass quantities, bacterial communities, and electrochemical kinetics

“…The second way of obtaining a biocathode is to polarize the electrode at a potential lower than the open circuit potential. The cathode polarization can result from MFC operation (potential may vary) [7][8][9][10] or from potentiostatic control (potential is constant) [11][12][13][14][15][16][17][18]. This method is widely used to form effective OR-biocathodes in many environments, among them sewage sludges or/and wastewater [8,13,15,18], industrial/agricultural wastes [7,9], seawater and sediments [14,17], soil and/ or derived leachate [10][11][12].…”

Microbial fuel cell: a green approach for the utilization of waste for the generation of bioelectricity

“…The results showed that chicken feathers can be successfully employed as a cheap substrate for electricity production in MFC. In a different study, rice straw hydrolysate was used for electricity production by Wang et al (2014). In presence of 400 mg-COD/L, a power density of 137.6 ± 15.5 mW/m 2 was obtained.…”

Improving the extracellular electron transfer of Shewanella oneidensis MR-1 for enhanced bioelectricity production from biomass hydrolysate

“…[1][2][3][4] Fueling MFC with renewable resources is now considered as one of the promising strategies to develop sustainable energy systems on earth. [5][6][7][8] Biomass is the most abundant renewable bioresource for sustainable bioenergy production. 9 For example, about 7 Â 10 8 tonnes of agricultural biomass could be produced annually in China.…”

“…12 Recently, MFCs fueled with wheat/rice straw hydrolysate were established with the mixed microbial community. 5,12 By using hydrothermal treated wheat straw hydralysate as the substrate, $148 mW m À2 power output was obtained by using a two chamber MFC inoculated with mixed microbial community. 12 Another biomass hydrolysate with about 1 time higher power output (293 mW m À2 ) was also developed by using acidic treated rice straw hydrolysate and anaerobic sludge as the substrate and inoculum, respectively.…”

“…12 Another biomass hydrolysate with about 1 time higher power output (293 mW m À2 ) was also developed by using acidic treated rice straw hydrolysate and anaerobic sludge as the substrate and inoculum, respectively. 5 However, the mixed culture encountered drawbacks such as difficult to be reproduced (esp. at different places or operation conditions), susceptible to environmental uctuation, complicated interspecies interaction, unknown mechanisms, and difficulty to control.…”